Immunisation and travel medicine
Routine immunisation across the life course plus pre-travel advice, malaria prophylaxis, and the fever cross-check.
- Immunisation is the single most effective preventive intervention in medicine: it trains the immune system to recognise a pathogen before it can cause disease, and it protects whole populations when coverage is high enough to interrupt transmission.
- A "schedule" is not a memorised list. It is a set of ages, intervals and doses that follow from how the immune system matures, from the epidemiology of each infection, and from the products available.
- Childhood and adult schedules differ by country and by edition. This topic mainly cites the United States Advisory Committee on Immunization Practices (ACIP) schedules for 2025, plus the CDC Yellow Book 2026 for travel. Use your own national calendar for exact timings at the bedside.
- Live attenuated vaccines (measles-mumps-rubella, varicella, yellow fever, oral typhoid, oral polio, rotavirus, BCG and the live influenza nasal spray) must not be given to anyone with significant immunodeficiency, and several have additional restrictions in pregnancy.
- Pre-travel advice is a risk assessment, not a prescription list: itinerary, duration, season, activities, traveller health and local epidemiology together decide which vaccines and which malaria prophylaxis make sense.
- Malaria chemoprophylaxis is highly effective but not perfect. Any fever in a traveller returning from a malaria-endemic area needs a blood smear within hours, even if they took every dose. This cross-check has its own MedGrasp topic, "Fever in a returned traveller".
- Low-resource note: when a vaccine or test is unavailable, the priority order is measles, tetanus-diphtheria, pertussis and hepatitis B for children, plus malaria prevention counselling and a smear for fever.
By the end of this page you should be able to:
- Explain the difference between live, inactivated, subunit, conjugate and toxoid vaccines, and why that distinction governs who may receive a vaccine.
- Outline the routine immunisation schedule for a child from birth to adolescence and for an adult, and justify the key intervals.
- State the principal contraindications and precautions for live vaccines, including the CD4 thresholds used in HIV infection and the corticosteroid dose that counts as high-dose.
- Conduct a pre-travel consultation: assess individual and itinerary risk, decide routine and travel vaccines, and choose appropriate malaria chemoprophylaxis.
- Choose and dose a malaria prophylactic drug, with the correct start, continuation and stop timings, and identify when G6PD testing is required.
- Recognise that fever in a recently returned traveller is malaria until proven otherwise, and describe the immediate diagnostic steps.
- Advise travellers on insect-bite prevention, self-treatment and insurance, and adjust advice for pregnancy, immunocompromise and limited resources.
Immunisation is the deliberate stimulation of the immune system so that a later encounter with a pathogen is cleared faster and with less illness. Vaccination is the act of giving a vaccine; immunisation is the immune response it produces. The two words are used interchangeably in clinical practice.
Vaccines come in five families that a medical student should keep distinct, because the family determines safety in immunocompromise:
- Live attenuated vaccines contain a weakened form of the organism that can still replicate. They mimic natural infection closely and usually give strong, long-lived immunity, often after one or two doses. The price is that they are unsafe in marked immunodeficiency and in pregnancy in several cases. Examples: measles-mumps-rubella (MMR), varicella, yellow fever, oral typhoid (Ty21a), BCG, rotavirus, oral polio and the live attenuated influenza nasal spray.
- Inactivated (killed) vaccines cannot replicate and are safe in immunocompromise, though they may need booster doses. Examples: inactivated polio, hepatitis A, rabies, Japanese encephalitis, inactivated influenza injection.
- Subunit, recombinant and conjugate vaccines use a piece of the organism, sometimes joined to a carrier protein to improve responses in young children. They are very safe and are the backbone of the infant schedule. Examples: hepatitis B, pneumococcal conjugate, meningococcal conjugate, Haemophilus influenzae type b (Hib), human papillomavirus (HPV).
- Toxoid vaccines use an inactivated bacterial toxin. Examples: tetanus and diphtheria.
- mRNA and viral vector vaccines encode an antigen in host cells. The COVID-19 vaccines are the common example; they are non-live and can be given in immunocompromise.
Two further ideas recur throughout schedules. A primary series is the set of doses that produces the first protective response. A booster re-exposes a primed immune system to raise antibody levels and prolong memory. Inactivated products usually need a primary series and periodic boosters; live products often do not.
DefinitionHerd immunity
When enough people in a community are immune, chains of transmission break and even people who cannot be vaccinated (newborns, the immunocompromised) are protected. The threshold varies from infection to infection: measles is one of the most contagious infections known, so it needs a very high proportion of the population to be immune.
The adult schedule assumes that routine childhood immunisation was completed. Its job is to fill gaps, cover age-related risks (influenza, pneumococcus, zoster), and protect in pregnancy and immunocompromise. The recommendations below are those of the ACIP adult schedule for 2025 (notes reviewed 2 July 2025), expressed as a guide rather than as a rule, and they change with each season for influenza and COVID-19. [1]
| Vaccine | Routine adult recommendation | Key interval or detail |
|---|---|---|
| Influenza | 1 dose every year for everyone aged 19 years or older | "Egg allergy" is no longer a contraindication to any influenza vaccine |
| COVID-19 | 1 dose of the current season's product for adults 19 to 64 years not pregnant; 2 doses at least 8 weeks apart for immunocompromised adults; adults 65 years or older receive a second dose 6 months later | Products are age- and manufacturer-specific [1] |
| Tetanus, diphtheria, pertussis | Complete a 3-dose primary series if unvaccinated; then Td or Tdap every 10 years; 1 dose of Tdap in each pregnancy, ideally at 27 to 36 weeks' gestation | Tdap is preferred as the first dose when the history is unknown [1] |
| Hepatitis B | Complete a 2-, 3- or 4-dose series for adults 19 to 59 years; risk-based or on request at 60 years or older | Heplisav-B is a 2-dose series at least 4 weeks apart; Engerix-B needs 3 doses at 0, 1 and 6 months [1] |
| Hepatitis A | 2-dose series on request for any unvaccinated adult (Havrix 6 to 12 months apart, or Vaqta 6 to 18 months apart, minimum 6 months) | Accelerated HepA-HepB (Twinrix) at 0, 7 and 21 to 30 days, then 12 months for travel, used in time-critical situations [1][2] |
| Human papillomavirus | Complete the series for everyone through 26 years; 2 doses 6 to 12 months apart if started at 9 to 14 years, 3 doses at 0, 1 to 2 and 6 months if 15 years or older; shared decision-making at 27 to 45 years | 3 doses for anyone immunocompromised, even if started young [1][2] |
| Measles, mumps, rubella | 1 dose if no evidence of immunity; 2 doses at least 4 weeks apart for students, travellers, contacts of immunocompromised people and health care staff | MMR is a live vaccine: avoid in severe immunocompromise [1] |
| Varicella | 2 doses 4 to 8 weeks apart if no evidence of immunity | Live vaccine: avoid in severe immunocompromise; give after pregnancy in women without immunity [1] |
| Zoster | 2-dose recombinant zoster vaccine (RZV, Shingrix) 2 to 6 months apart from age 50 years, regardless of prior shingles or Zostavax | Minimum interval 4 weeks; also for immunocompromised adults at high risk [1][2] |
| Pneumococcal | Adults 50 years or older: 1 dose of PCV15, PCV20 or PCV21; if PCV15 is used, add PPSV23 at least 1 year later (8 weeks is acceptable if immunocompromised) | Adults 19 to 49 years receive it only with risk factors [1] |
| Polio | Adults known or suspected to be unvaccinated or incompletely vaccinated: 1, 2 or 3 doses of inactivated polio vaccine to complete a 3-dose primary series | A single lifetime booster for adults at increased exposure [1] |
| Meningococcal | Special situations only: 2-dose primary series for asplenia, complement deficiency or travel in hyperendemic areas, then boosters every 5 years | Menveo, MenQuadfi and MenB products differ [1][2] |
| Respiratory syncytial virus | Pregnant women at 32 weeks 0 days to 36 weeks 6 days during September to January: 1 dose of Abrysvo; adults 75 years or older: 1 dose; adults 50 to 74 years at increased risk: 1 dose | Either maternal RSV vaccination or infant nirsevimab, not both routinely [1] |
| Hepatitis A (travel) | Standard 2-dose series protects against travel-acquired hepatitis A, the most common vaccine-preventable infection acquired abroad | Dose 1 as soon as travel is considered for unvaccinated adults [2] |
Special vaccination needs push the adult schedule in three directions. Adults with asplenia need pneumococcal, meningococcal (ACWY and B), Hib and influenza protection, with splenectomy ideally preceded by vaccination at least 14 days before. Adults with HIV should receive MMR only if their CD4 count is at least 200 cells per cubic millimetre and CD4 percentage at least 15%, and varicella only if CD4 is at least 200 cells per cubic millimetre; both are live and are contraindicated below those levels. Adults receiving immunosuppressive therapy should ideally have all live vaccines completed before treatment starts, and live vaccines are withheld for 3 months after immunosuppressive drugs and 6 months after anti-B-cell agents. [1][3]
Two adult vaccines deserve special emphasis for travel. Hepatitis A is one of the most common vaccine-preventable diseases acquired during travel, so an unvaccinated adult visiting an intermediate or high endemicity area should receive dose 1 as soon as the trip is planned. Hepatitis B is recommended for travellers to countries with hepatitis B surface antigen prevalence of 2% or higher, and can be considered for any traveller because sexual, medical or injury-related exposure is unpredictable abroad. [4]
The infant and childhood schedule exploits two windows: maternal antibody fades in the first months, opening the way for the infant's own responses, and school entry concentrates transmission. The programme below is the United States child and adolescent schedule for 2025 (notes dated 2 July 2025). Your national schedule may differ in product and timing, but the principles are the same everywhere.
| Age | Vaccines given | Key points |
|---|---|---|
| Birth | Hepatitis B dose 1 within 24 hours if the mother is surface-antigen negative and birth weight is 2,000 g or more; if the mother is surface-antigen positive, hepatitis B vaccine plus immune globulin in separate limbs within 12 hours, regardless of weight | Birth weight under 2,000 g: delay the birth dose to 1 month or discharge [2] |
| 2, 4 and 6 months | DTaP, Hib, inactivated polio, pneumococcal conjugate, rotavirus (oral, live), hepatitis B | Rotavirus course must be completed by 8 months |
| 12 to 15 months | First dose of MMR, varicella, hepatitis A dose 1, and a Hib booster | MMRV may be used from 12 months but separate MMR and varicella are preferred for the first dose |
| 15 to 18 months | Fourth dose of DTaP | |
| 4 to 6 years | Fifth dose of DTaP, second dose of MMR, second dose of varicella | |
| 11 to 12 years | Tdap booster, first dose of meningococcal ACWY, and HPV vaccination (may start at 9 years) | HPV is 2 doses 6 to 12 months apart if started at 9 to 14 years [2] |
| 16 years | Second dose of meningococcal ACWY | |
| 6 months and older | Influenza every year | Children 6 months to 8 years who have had fewer than 2 influenza doses previously need 2 doses at least 4 weeks apart [2] |
| 9 to 16 years in endemic areas | Dengue vaccine only for those with laboratory-confirmed prior dengue infection | 3 doses at 0, 6 and 12 months; not for travellers briefly visiting endemic areas [2] |
| 16 to 23 years | Meningococcal B on the basis of shared clinical decision-making | 2 doses at least 6 months apart [2] |
The childhood schedule contains important subtleties that exam questions test repeatedly:
- Hepatitis B at birth is the only vaccine routinely given before any other immunisation, because perinatal transmission is the most efficient route and because maternal antibody does not block this response. Infants born to mothers with chronic hepatitis B receive vaccine plus hepatitis B immune globulin within 12 hours.
- DTaP (diphtheria, tetanus and acellular pertussis) needs five doses, with the fifth being unnecessary if the fourth was given at four years or older at least 6 months after the third. [2]
- MMR is given at 12 to 15 months and 4 to 6 years. For travel, infants aged 6 to 11 months who are going to measles-endemic areas (which includes much of the world) should receive 1 dose before departure, then be revaccinated with the full 2-dose series from 12 months, with dose 2 no earlier than 4 weeks later. The same applies to hepatitis A in the infant traveller. [2]
- Varicella vaccine is a live vaccine, and its minimum age is 12 months. When MMR and varicella are given together at 12 to 47 months, the combination can slightly increase the risk of fever-related fits compared with giving them separately, so many programmes give MMR and varicella as separate injections at the first dose.
- Hib products differ: ActHIB, Hiberix and Pentacel need a 4-dose series, while PedvaxHIB needs only 3 doses with the last two at 2 and 4 months and a booster at 12 to 15 months. Vaxelis cannot be used for the booster dose. [2]
- Human papillomavirus vaccine protects against cancers caused by oncogenic types. Starting between 9 and 14 years gives immunity with 2 doses; starting at 15 years or older needs 3 doses. The routine age is 11 to 12 years, but it can begin at 9. [2]
- Meningococcal vaccine in adolescence protects against a rare but rapidly fatal infection. Routine ACWY is at 11 to 12 and 16 years. Serogroup B vaccine is given at 16 to 23 years on shared clinical decision-making; it is 2 doses at least 6 months apart. [2]
Catch-up is allowed and never requires restarting a series. Doses given up to 4 days before the minimum age or interval are accepted; doses given 5 or more days early must be repeated after the correct minimum interval. [1][2]
Live vaccines should be avoided in pregnancy and in significant immunocompromise, but they are often safe in HIV infection when immunity is preserved. The table summarises the standard guidance, mostly from the ACIP general best practice document on altered immunocompetence. [3]
| Live vaccine | Main contraindications and cautions |
|---|---|
| MMR (and MMRV) | Severe cellular immunodeficiency; CD4 below 15% or fewer than 200 cells per cubic millimetre in HIV infection. Safe and recommended for HIV infection with CD4 at least 15% and at least 200 cells per cubic millimetre for at least 6 months |
| Varicella (single antigen) | Severe immunodeficiency; CD4 below 15% or fewer than 200 cells per cubic millimetre. May be considered in HIV infection with CD4 at least 15% and at least 200 cells per cubic millimetre: 2 doses 3 months apart. MMRV is never given to an HIV-infected person [3] |
| Yellow fever | Severe immunodeficiency. Contraindicated if symptomatic HIV infection or CD4 below 200 cells per cubic millimetre; a precaution only if 200 to 499 cells per cubic millimetre [3] |
| Oral typhoid (Ty21a) BCG, smallpox (vaccinia) | Avoid in most altered immunocompetence. BCG additionally avoided in suspected severe combined immunodeficiency |
| Rotavirus (oral) | Avoid in severe combined immunodeficiency and in infants with a history of intussusception |
| Live attenuated influenza (nasal) | Avoid in pregnancy, severe immunocompromise, and asplenia; may be given to healthy household contacts of immunocompromised people unless the immunocompromised person is in a protective environment |
| Oral polio | No longer used in the United States; inactivated polio is used instead |
Two safety thresholds are worth memorising precisely.
DefinitionHigh-dose corticosteroids
A dose equivalent to at least 2 milligrams per kilogram of body weight per day, or at least 20 milligrams per day of prednisolone or equivalent for people weighing more than 10 kilograms, given for 14 consecutive days or more, suppresses immunity enough to raise concern about live vaccines. Vaccination should be deferred for at least 1 month after such a course ends. Shorter courses, low doses, alternate-day therapy, replacement doses and topical, inhaled or intra-articular steroids are not usually contraindications to live vaccination. [3]
- All non-live vaccines are safe in immunocompromise. The concern with them is reduced effectiveness, which is why timing matters: a non-live vaccine given within 14 days before or during immunosuppressive therapy may need to be repeated once immune function recovers. [3]
- Household and close contacts of an immunocompromised person should be vaccinated with MMR, varicella and rotavirus when indicated. The live virus can in theory be shed, but the risk to the contact is far smaller than the risk of introducing wild-type infection, and only a varicella rash after vaccination requires avoiding contact until it has resolved.
- Yellow fever vaccine carries a specific precaution-contraindication grading based on CD4 count, so a traveller with moderate immunodeficiency needs individual risk-benefit discussion rather than automatic refusal.
United States
The United States schedule separates MMR and varicella at the first dose between 12 and 47 months because MMRV given together in this age group carries a higher rate of fever and febrile convulsions.
World Health Organization
National immunisation programmes adapt the World Health Organization expanded programme on immunisation to local disease burden, cold-chain capacity and cost. In regions with high measles transmission, an extra measles dose at 9 months may be used, and tuberculosis vaccination with BCG is routine at birth.
Pre-travel advice is a consultation, not a form. It consists of a risk assessment, clear communication of those risks, and risk reduction. The three components overlap, and together they determine which vaccines and which malaria prophylaxis make sense. The framework below is that of the CDC Yellow Book 2026 chapter on the pre-travel consultation.
No itinerary is complete without the traveller's own profile. The assessment includes:
- Health background: age, allergies (especially to vaccines, eggs or latex), current medications, underlying conditions, and pregnancy or breastfeeding status.
- Special conditions: recent surgery or cardiopulmonary event, immunocompromise, seizure disorder, recent chemotherapy, thymus abnormality, and advanced age.
- Immunisation history: routine vaccines already given, and any travel vaccines.
- Prior travel experience: previous malaria chemoprophylaxis, malaria infections, altitude illness and travel-related infections.
- Itinerary: countries, regions (urban versus rural), order of countries, and layovers.
- Timing: season, departure date and trip duration.
- Reason for travel: tourism, visiting friends and relatives, business, pilgrimage, adventure, medical care abroad.
- Travel style: accommodation standard, independence, and travel with children.
- Special activities: animal contact, fresh water exposure, trekking, motorbiking, health care work, diving or high altitude.
Visiting friends and relatives is the single highest-risk reason for travel in many countries, because travellers assume residual immunity that has actually faded and because they often stay in rural settings.
Communicate risk in plain language. Travellers vary enormously in their tolerance for risk, and the consultation is an exchange rather than a lecture.
Managing risk means:
- Updating routine vaccines (the yellow book table lists both routine and travel-specific ones).
- Deciding travel vaccines from itinerary and activities.
- Prescribing malaria prophylaxis where indicated, and teaching adherence.
- Teaching mosquito avoidance, food and water precautions, injury prevention and behavioural risks (road traffic, sexual health, blood-borne exposures).
- Providing self-treatment for likely problems such as travellers' diarrhoea, motion sickness and altitude illness.
- Advising on travel insurance, evacuation and how to find reliable care abroad.
Clinical pearlCost and prioritisation
Some travellers cannot afford every recommended intervention. When resources are tight, prioritise interventions by the seriousness and the likelihood of the hazard: measles and routine vaccines for children, malaria prophylaxis for a high-burden destination, and Japanese encephalitis or rabies pre-exposure only when the itinerary genuinely warrants it.
Last-minute travellers need attention too: many vaccine series cannot be completed (Japanese encephalitis needs two doses 28 days apart, rabies three), but accelerated schedules and first doses with follow-up after travel are still useful.
| Vaccine | Travel recommendation |
|---|---|
| Hepatitis A | One of the most common vaccine-preventable infections acquired during travel. Vaccinate (or give immunoglobulin) anyone going to a country with high or intermediate endemicity. Dose 1 as soon as travel is considered |
| Hepatitis B | Recommended for travellers to countries with hepatitis B surface antigen prevalence of 2% or more, and can be considered for all travellers |
| Measles, mumps, rubella | International travellers of 6 months or older without immunity need protection; outbreaks in the United States are frequently traced to imported infection [4] |
| Meningococcal (A, C, W, Y) | Recommended for the "meningitis belt" of sub-Saharan Africa during the dry season, and the Hajj requires the quadrivalent vaccine for pilgrims [4] |
| Yellow fever | Offer to eligible travellers to endemic parts of sub-Saharan Africa and South America; assess absolute and relative contraindications individually, and give a medical waiver when vaccination is unsafe |
| Typhoid | Recommended for travellers with prolonged exposure to potentially contaminated food and drink in developing regions |
| Japanese encephalitis | Rare, but severe; vaccinate longer-term travellers (about a month or more) and frequent visitors to endemic areas |
| Rabies | Pre-exposure immunisation for travellers whose activities may put them at risk, and for whom post-exposure prophylaxis would be hard to obtain abroad |
| Cholera | Consider for travel to areas with active transmission in the last 12 months [4] |
| Tick-borne encephalitis | Endemic areas in Europe; consider for travellers with extensive tick exposure |
| Influenza and COVID-19 | Keep up to date: transmission is seasonal in temperate zones and year-round in the tropics |
| Polio | Unimmunised or under-immunised travellers can acquire wild or vaccine-derived poliovirus; adults who completed the childhood series and travel to higher-risk destinations may receive one lifetime booster dose |
Air travel itself carries restrictions: it is usually contraindicated within 2 weeks of an uncomplicated myocardial infarction and within 10 days of thoracic or abdominal surgery, and other conditions need destination-specific advice. [4]
- Personal protection: seat belts, helmet use, safe alcohol and sexual practices, avoidance of animal contact (rabies), fresh water (schistosomiasis, leptospirosis) and barefoot walking (parasites).
- Vector avoidance: DEET-containing repellent applied after sunscreen, permethrin on clothing and nets, covering clothing, and sleeping in screened or air-conditioned rooms. Repellent-impregnated clothing is an option.
- Sun and water: sun protection and safe water and food practices, plus diarrhoea self-treatment.
- Self-treatment supplies: for travellers' diarrhoea, altitude illness, motion sickness, malaria (a reliable supply), and common problems such as urinary or yeast infections.
A pre-travel consultation in outline
- 1. Assess the travellerHealth background, allergies, medications, pregnancy, immunocompromise, immunisation history
- 2. Assess the itineraryCountries, regions, season, duration, reason, activities
- 3. Communicate riskPlain-language hazards and personal tolerance for risk
- 4. Manage routine immunisationUpdate influenza, COVID-19, tetanus-diphtheria-pertussis, MMR, varicella, hepatitis B, HPV as needed
- Question: Is the destination malaria-endemic?
No
- 5. Give travel-specific vaccines onlyHepatitis A, yellow fever, typhoid, rabies, Japanese encephalitis, meningococcal, cholera, TBE as indicated
Yes
- 5. Give travel-specific vaccinesAs above, plus confirm yellow fever requirements
- 6. Choose malaria prophylaxisDestination species and resistance, trip length, pregnancy, other conditions, allergies, cost
- 7. Teach mosquito avoidance and self-treatmentDEET, permethrin, nets, repellent clothing; reliable supply where appropriate
- 8. Document and arrange follow-upYellow card, completion dates, travel insurance and evacuation plan
Malaria is caused by Plasmodium parasites that a female Anopheles mosquito transmits mainly between dusk and dawn. It is a major global health problem: the World Health Organization's World Malaria Report 2024 recorded about 263 million infections and 597,000 deaths in 83 endemic countries during 2023. For travellers, the burden is concentrated: roughly 93% of imported malaria cases in the United States are acquired in Africa, and most occur in people visiting friends and relatives. [5]
Prevention has two parts that are used together: mosquito avoidance and chemoprophylaxis. No prophylactic drug is 100% effective, so chemoprophylaxis must be paired with bite prevention.
Risk varies with the intensity of local transmission, exact itinerary, trip duration, season, style of travel, and the traveller's own characteristics, including pregnancy and immunocompromise. Risk tends to be higher for:
- rural accommodation without screens or air conditioning;
- travel in peak transmission season;
- short travel to high-transmission areas;
- people visiting friends and relatives, who often assume immunity they no longer have.
Partial immunity acquired through childhood exposure fades quickly. Treat a returning visitor as a non-immune traveller.
- Remaining in enclosed, air-conditioned or well-screened areas where possible.
- Sleeping under insecticide-treated nets.
- Using insecticide sprays or mosquito coils in living and sleeping areas at night.
- Wearing clothing that covers most of the body in the evening.
- Applying an effective repellent (DEET-containing) to exposed skin, after sunscreen if both are used.
- Considering permethrin-treated clothing and nets.
- Travellers should take repellent and net with them rather than relying on local supply.
The choice depends on destination resistance, trip length, pregnancy, other medical conditions, medications and cost, and on whether the traveller can tolerate daily or weekly dosing. G6PD deficiency must be excluded with a quantitative test before using primaquine or tafenoquine, because both can cause haemolysis.
| Drug | Adult dose and schedule | Main cautions |
|---|---|---|
| Atovaquone-proguanil | 1 adult tablet daily, starting 1 to 2 days before travel, continuing daily in the endemic area, and for 7 days after leaving | Not for pregnant women, breastfeeding of infants under 5 kg, or severe renal impairment (creatinine clearance under 30 millilitres per minute). Good choice for last-minute travellers [5] |
| Doxycycline | 100 milligrams daily, starting 1 to 2 days before travel and for 4 weeks after leaving | Contraindicated in pregnancy and in children under 8 years. Photosensitivity and oesophagitis; take with fluids and avoid lying down [5] |
| Mefloquine | 228 milligrams (salt 250 milligrams) weekly, starting at least 2 weeks before travel and for 4 weeks after leaving | Contraindicated in active or recent depression, anxiety disorder, psychosis, schizophrenia and seizures; avoid in cardiac conduction abnormalities. FDA boxed warning for neuropsychiatric effects. Not for last-minute travel [5] |
| Chloroquine | 300 milligrams base (500 milligrams salt) weekly, starting 1 to 2 weeks before travel and for 4 weeks after leaving | Only for chloroquine-sensitive Plasmodium species. Can exacerbate psoriasis [5] |
| Hydroxychloroquine | 310 milligrams base (400 milligrams salt) weekly, same timing as chloroquine | Alternative to chloroquine in chloroquine-sensitive areas [5] |
| Primaquine | 30 milligrams base daily, starting 1 to 2 days before travel, for 7 days after leaving | Only after documented normal G6PD. Contraindicated in pregnancy and breastfeeding unless the infant's G6PD is normal. Good for short trips to mostly vivax areas [5] |
| Tafenoquine | 200 milligrams daily for 3 days before travel, then 200 milligrams weekly, plus 1 dose in the week after leaving | Only after documented normal G6PD. Not for children, pregnancy or breastfeeding without normal infant G6PD [5] |
The destination's resistance pattern decides which drug is usable. Chloroquine-resistant P. falciparum exists in all of Africa, Asia and South America except the Caribbean and Central America west of the Panama Canal, so atovaquone-proguanil, doxycycline, mefloquine or tafenoquine are used there. Mefloquine-resistant P. falciparum is reported in parts of Southeast Asia, so atovaquone-proguanil, doxycycline or tafenoquine are used there. Chloroquine-resistant P. vivax has been confirmed in Papua New Guinea and Indonesia.
By pregnancy, the options narrow. Chloroquine and mefloquine can be used in all trimesters, hydroxychloroquine is an alternative, while atovaquone-proguanil, doxycycline, primaquine and tafenoquine are not used in pregnancy. Travellers in their first trimester who cannot tolerate a safe drug should reconsider travel to a high-transmission area. [5]
Two additional points from the malaria chapter are worth stating because they affect decisions:
- Screening children for G6PD deficiency is required before primaquine or tafenoquine in both adults and breastfed infants, and a normal result, once documented, does not need repeating.
- Malaria chemoprophylaxis, while highly effective, is not 100% effective. The single most important safety message is that a traveller who develops fever after returning must seek care immediately.
Chemoprophylaxis is not treatment. A traveller already ill with malaria needs a treatment course, and a traveller in a remote area may carry a reliable supply of atovaquone-proguanil (4 adult tablets daily for 3 consecutive days) or artemether-lumefantrine (initial dose, second dose 8 hours later, then 1 dose twice daily for 2 days, 6 doses over 3 days). The drug carried must differ from the one used for prophylaxis, and self-treatment is only a bridge to urgent care. [5]
Choosing malaria chemoprophylaxis for a traveller
- Confirm malaria-endemic destinationUse country-specific CDC or WHO tables, by exact region, season and accommodation
- Question: Is the traveller pregnant?
Yes
- Use chloroquine or mefloquine (all trimesters) or hydroxychloroquineAvoid atovaquone-proguanil, doxycycline, primaquine and tafenoquine
No
- Question: Is the species in the area chloroquine-sensitive?
Yes
- Options: chloroquine, hydroxychloroquine, atovaquone-proguanil, doxycycline, mefloquine, tafenoquinePrimaquine is a further option where vivax predominates
No (chloroquine-resistant)
- Options: atovaquone-proguanil, doxycycline, mefloquine, tafenoquineAtovaquone-proguanil 1 to 2 days before; doxycycline 1 to 2 days before; mefloquine at least 2 weeks before; tafenoquine loading 3 days before
- Apply traveller constraintsAge under 8 years excludes doxycycline; under 5 kg excludes atovaquone-proguanil; renal impairment excludes atovaquone-proguanil; psychiatric history excludes mefloquine; G6PD deficiency excludes primaquine and tafenoquine
- Advise adherence and bite preventionStart on time, continue after return, finish the course, never stop because of mild side effects without consulting a clinician
Fever in someone who has recently returned from a malaria-endemic area is malaria until proven otherwise. Malaria, especially P. falciparum, is a medical emergency: deterioration and death can be rapid and unpredictable. The malaria chapter states the cross-check explicitly, and its handling has its own MedGrasp topic, "Fever in a returned traveller".
| Question | Action |
|---|---|
| Did fever develop during travel or after return from an endemic area? | Consider malaria whatever the chemoprophylaxis history, since prophylaxis is not 100% effective [5] |
| How soon can malaria appear? | As early as 7 days after the bite and as late as several months, or longer for vivax and ovale [5] |
| What tests? | Blood smear microscopy with results available as soon as possible and within 24 hours of presentation, plus a rapid diagnostic test if it returns faster; PCR to confirm species [5] |
| When to start treatment? | Once the diagnosis is confirmed, immediately; if severe malaria is suspected and testing is not immediately available, start treatment before the diagnosis is established |
| Must chemoprophylaxis continue during investigation? | Yes, until the diagnosis is ruled out or confirmed |
| In every case | Report travel history, report malaria as required by local law, contact expert help early (in the United States, the CDC malaria hotline) |
Drug exposure matters for diagnosis too. Chloroquine is contraindicated in many areas, and halofantrine is not recommended for treatment because of documented fatal cardiac events. Self-treatment with a carried supply is only a temporary measure.
Pregnancy. Inactivated vaccines are safe and live vaccines are avoided. Tdap is given in every pregnancy at 27 to 36 weeks' gestation to protect the newborn from pertussis. Tdap and influenza are given in pregnancy; COVID-19 is given according to current seasonal guidance. For travel, chloroquine and mefloquine (or hydroxychloroquine) are the malaria prophylactic options, and yellow fever requires careful individual risk-benefit assessment.
Children and infants. The infant schedule immunises against the diseases most dangerous and most transmissible in early life. For travel, remember the 6-to-11-month measles dose and the infant hepatitis A dose, the need to avoid dengue vaccine in short-stay travellers, and the need to avoid live vaccines in pregnancy and severe immunodeficiency. When a mother is travelling with an infant, maternal antibody may blunt early responses to some products, which is why certain vaccines are timed to after 12 months. [2]
Immunocompromised travellers. Inactivated vaccines should be brought up to date, live vaccines avoided or given only at appropriate CD4 levels, and the traveller should be advised that vaccines may be less effective. All close contacts should be fully vaccinated.
Older adults. Influenza annually, COVID-19 per season, zoster from 50 years, pneumococcal from 50 years, RSV from 60 years (or 50 years with risk factors; 75 years and older routinely), and a tetanus-containing booster every 10 years. Older skin is also slower to heal, so travel injury prevention matters more.
- Immunise first: BCG at birth where tuberculosis is endemic, and the infant series (diphtheria-tetanus-pertussis, hepatitis B, Hib, pneumococcal if available, polio, rotavirus, measles) on the national schedule.
- Measles kills most where coverage is low. Measles vaccination is the priority at 9 or 12 months according to local policy.
- Cold chain: killed (inactivated) vaccines tolerate freezing poorly in some cases and heat sensitivity varies; follow storage rules strictly.
- When malaria testing is unavailable, a clinical diagnosis with fever in an endemic area still warrants prompt antimalarial treatment for suspected severe malaria; do not wait for a test that will not arrive in time.
- When antimalarial drugs are unavailable locally, travellers and residents should carry a verified supply from a reliable source and avoid counterfeit products.
- With no travel clinic, use the public health department or the CDC travelled-health country pages to decide malaria prophylaxis by destination.
- Immunisation schedules follow immune maturation, epidemiology and product availability; they vary by country and are updated regularly.
- Live attenuated vaccines give strong immunity but are avoided in significant immunodeficiency and in many cases in pregnancy.
- The routine adult schedule turns on influenza every year, tetanus-containing booster every 10 years, pneumococcal conjugate from 50 years, zoster from 50 years and respiratory syncytial virus in older adults.
- Childhood schedules centre on the birth-dose of hepatitis B, a 3-4 dose infant series, MMR and varicella at 12 to 15 months and 4 to 6 years, HPV at 11 to 12 years and a meningococcal booster at 16 years.
- Two live-vaccine thresholds to memorise: varicella and MMR are usable in HIV only with CD4 at least 15% and 200 cells per cubic millimetre; live vaccines are unsafe with high-dose corticosteroids (at least 2 milligrams per kilogram per day or at least 20 milligrams per day for 14 days or more). [3]
- A pre-travel consultation assesses the traveller and the itinerary, updates routine vaccines, adds travel-specific vaccines and considers malaria prophylaxis, mosquito avoidance, self-treatment and behaviour.
- Malaria prophylaxis uses drugs with different start and stop timings: atovaquone-proguanil 1 to 2 days before and 7 days after; doxycycline and primaquine 1 to 2 days before and 4 or 7 days after; mefloquine at least 2 weeks before and 4 weeks after; tafenoquine loading 3 days before and one dose after.
- Primaquine and tafenoquine require documented normal G6PD levels. Atovaquone-proguanil, doxycycline, primaquine and tafenoquine are not used in pregnancy. [5]
- Fever after travel to a malaria-endemic area is malaria until proven otherwise: seek care immediately, test urgently and continue prophylaxis during the workup.
Answer each one in your head first, then open the answer.
A traveller has no documented measles immunity and is visiting India. What immunisation advice is appropriate, and what is the minimum interval?
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He needs MMR vaccination before travel: 2 doses at least 4 weeks apart for an international traveller without evidence of immunity. Because he travels in under a month, give dose 1 now and dose 2 at least 4 weeks later, even if this falls during travel, and counsel on measles risk until fully protected. India does not change the MMR schedule, but many travellers are under-immunised. [1]
An infant is about to travel to a measles-endemic country. What should be done?
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Give 1 dose of standard MMR now (minimum age for the routine schedule is 12 months, so this is an off-schedule travel dose). Revaccinate with the full 2-dose series from 12 months of age, with dose 2 given no earlier than 4 weeks after the first dose. Document the travel dose and explain to the parents that it does not count as a routine dose.
A woman with HIV and a CD4 count well above 200 cells per cubic millimetre asks for varicella vaccination before travel. Is it safe?
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Yes, with conditions. Single-antigen varicella may be considered in HIV when the CD4 proportion is at least 15% and the count is at least 200 cells per cubic millimetre: 2 doses 3 months apart. The combination MMRV must not be given to her. Confirm that no contraindication on the basis of symptoms of a primary or acquired immunodeficiency applies, and document the CD4 result and date.
A traveller is leaving in 5 days for a rural area of East Africa at the height of transmission. Which malaria prophylactic is most suitable if he is healthy, adult and takes no regular medicines, and why?
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Atovaquone-proguanil started 1 to 2 days before travel, continued daily in the endemic area and for 7 days after return. It is suitable for last-minute travellers, is generally well tolerated, and is also one of the recommended drugs for chloroquine-resistant areas. Doxycycline started 1 to 2 days before would also work; mefloquine is unsuitable because it needs at least 2 weeks to start. Chloroquine is not suitable for most of Africa because of resistance.
Which of the live vaccines may be given to a child with severe combined immunodeficiency?
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None of them. Severe combined immunodeficiency is a contraindication to all live viral and live bacterial vaccines. The child instead receives protection from non-live products, immunoglobulin replacement where indicated and from herd immunity, and referral to specialist immunology care.
A traveller returns from West Africa with fever shortly after arrival. She completed every dose of her chemoprophylaxis. What should happen next?
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Malaria must be excluded regardless of prophylaxis, because no regimen is 100% effective. Arrange urgent malaria blood smear microscopy (results within 24 hours and ideally much sooner), a concurrent rapid diagnostic test, and expert clinical review. Do not delay treatment if severe malaria is suspected and testing is not immediately available. Report the travel history clearly and arrange follow-up.
Why is hepatitis B vaccine given at birth, even though most other infant vaccines start at 2 months?
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Perinatal transmission is the most efficient route for hepatitis B, and maternal antibody does not blunt the response to this vaccine. Giving it within 24 hours to infants of surface-antigen-negative mothers (and within 12 hours with immune globulin to infants of positive mothers) prevents infection that would otherwise become chronic with high frequency in infancy.
- Fever in a returned traveller (the cross-check for malaria diagnosis and differential diagnosis).
- Travel-specific infections such as yellow fever, rabies, dengue and travellers' diarrhoea, each covered in its own MedGrasp topic where available.
- Routine antenatal care: a separate topic covers pregnancy immunisation in detail.
- Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices. Recommended Adult Immunization Schedule for Ages 19 Years or Older: Notes (United States, 2025). CDC Vaccines & Immunization, schedule notes last revised 2025-07-02. Accessed .
- Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices. Recommended Child and Adolescent Immunization Schedule for Ages 18 Years or Younger: Notes (United States, 2025). CDC Vaccines & Immunization, schedule notes dated 2025-07-02. Accessed .
- Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices. General Best Practice Guidelines for Immunization: Altered Immunocompetence. CDC Vaccines & Immunization, last reviewed 2024-06-26. Accessed .
- Chen LH, Bourque DL. The Pre-Travel Consultation (CDC Yellow Book 2026). CDC Yellow Book: Health Information for International Travel, 2026 edition, published 2025-04-23. Accessed .
- Ridpath AD, Wallender E. Malaria (CDC Yellow Book 2026). CDC Yellow Book: Health Information for International Travel, 2026 edition, published 2025-04-23. Accessed .
Educational content for medical students and doctors. It is not a substitute for clinical judgement or local guidelines.