Malaria Prophylaxis: The Options, How They Differ and Why Timing Matters

A nurse in a travel clinic told me the busiest week of her year is no longer the run-up to Christmas. It is the stretch when wedding invitations from Lagos, Accra and Mumbai land in the same inbox as a viral video insisting that mosquito repellent makes the pills unnecessary. As of July 2025, searches for malaria prophylaxis have climbed on the back of three things: the World Health Organization’s latest World Malaria Report, which counted an estimated 263 million cases and 597,000 deaths worldwide in 2023; the 2026 edition of the CDC’s travel medicine reference, the Yellow Book, published this year; and a steady flow of social media posts promising natural alternatives to the tablets.

That mix of real news and loud rumor is exactly where people get hurt. Every year roughly 2,000 travelers return to the United States with malaria, and the great majority were either not taking prophylaxis or not taking it as prescribed.

This piece walks through what the medicines are, how they differ, why the calendar matters as much as the pharmacology, and where the evidence is solid, moderate or thin.

Why malaria prophylaxis is suddenly everywhere in search

Search spikes rarely have one cause, and this one has at least three. The first is simple exposure: international travel to sub-Saharan Africa and South Asia has rebounded past pre-pandemic levels, and more people are visiting family rather than staying in air-conditioned resorts. Family visits mean longer stays, rural overnights and evenings outdoors, which is exactly when the Anopheles mosquito that carries malaria likes to feed.

The second is news. The WHO’s World Malaria Report, released in December 2024, confirmed that malaria deaths have not fallen meaningfully since 2015, and that children under five still account for about three in four malaria deaths in Africa. At the same time, two malaria vaccines are being rolled into childhood immunization programs across the continent, which has left many adults wondering, reasonably, whether a vaccine exists for them. It does not, at least not yet, and that gap sends people straight back to the tablets.

The third driver is the one that worries clinicians: viral content. Short videos claiming that garlic, vitamin B1, tonic water or a particular essential oil blend will prevent malaria have racked up millions of views. None of these claims is supported by controlled trials, and some are actively dangerous because they persuade travelers to skip prophylaxis altogether.

What all three threads share is a question people type into a search bar at eleven at night, two weeks before a flight: what are my options, and when do I need to start? The honest answer is that malaria prophylaxis is a decision made with a clinician who knows your itinerary, your medical history and the current resistance patterns where you are going. The rest of this article exists to make that conversation shorter and sharper.

What changed recently in malaria prevention

Several dated developments explain the current attention, and they are worth separating from the noise.

December 2024. The WHO World Malaria Report estimated 263 million malaria cases and 597,000 deaths in 2023, an increase of around 11 million cases over the previous year. Roughly 94 percent of cases and 95 percent of deaths occurred in the WHO African Region. The report also noted that resistance of the Plasmodium falciparum parasite to artemisinin, the backbone of malaria treatment, has now been confirmed in several East African countries.

2024. The WHO consolidated its malaria guidelines, including updated recommendations on chemoprevention for children and pregnant women living in endemic areas. These are population strategies for residents, not travel advice, but they often get quoted out of context online.

2025. The CDC published the 2026 edition of its Yellow Book, which lists country-by-country malaria risk, the parasite species present, known drug resistance and the prophylaxis options it considers appropriate for each destination. Clinicians use this as the primary reference when choosing a regimen for American travelers.

2023, still shaping guidance. The United States recorded its first locally acquired malaria cases in two decades, in Florida, Texas, Maryland and Arkansas. The numbers were tiny, fewer than a dozen, and transmission did not persist, but the episode reminded clinicians that Anopheles mosquitoes still live in much of the country.

Vaccines. Since late 2023, the RTS,S/AS01 and R21/Matrix-M vaccines, both recommended by the WHO for children in moderate to high transmission areas, have entered routine immunization schedules in a growing list of African countries. Neither vaccine is licensed or recommended for travelers.

None of these changes altered the fundamental menu of travel antimalarials, which has been stable since tafenoquine was approved by the US Food and Drug Administration in 2018. What has changed is the volume of people asking about it.

What is malaria prophylaxis and how does it actually work?

Prophylaxis is a medicine taken to prevent a disease rather than treat it. In malaria, the medicine is working against a parasite with an unusual life cycle, and that life cycle is the key to understanding why the options differ.

Malaria is caused by single-celled parasites of the genus Plasmodium. Five species infect humans: P. falciparum, responsible for most severe disease and deaths; P. vivax and P. ovale, which can form dormant liver forms called hypnozoites that reawaken months later; P. malariae; and P. knowlesi, a monkey parasite found in parts of Southeast Asia.

When an infected female Anopheles mosquito bites, usually between dusk and dawn, she injects sporozoites, the travel-stage form of the parasite. Within about an hour these reach the liver, where each one quietly multiplies for one to two weeks. The liver stage causes no symptoms. The parasites then burst into the bloodstream, invade red blood cells and begin the cycles of multiplication and cell rupture that produce fever, chills and sweats.

Antimalarials attack different points on this map. Causal prophylaxis acts on the liver stage, stopping the infection before it ever reaches the blood. Atovaquone-proguanil, primaquine and tafenoquine work this way. Suppressive prophylaxis acts only on the blood stage, which means parasites may complete their liver development after you leave the risk area and emerge into blood that still needs to contain the drug. Chloroquine, mefloquine and doxycycline fall into this category.

That one distinction explains the central timing fact of this whole topic: suppressive drugs must be continued for about four weeks after the last possible bite, while causal drugs can stop within about a week. It is biology, not marketing, that sets the calendar.

Which malaria prophylaxis options exist today?

In the United States, five prescription medicines are used for travel prophylaxis, with a sixth used in a narrow situation. Each carries a different profile, and no single one suits every traveler.

Atovaquone-proguanil (Malarone). A fixed combination of two drugs that together block the parasite’s energy production and DNA synthesis. It is taken daily, works on the liver stage, and is generally the best tolerated option. It is not recommended in severe kidney impairment or during pregnancy, and small children are dosed by weight under supervision.

Doxycycline. A tetracycline antibiotic that also kills the blood-stage parasite. Taken daily, it is widely available and has the added benefit of some protection against other travel infections such as leptospirosis. It is not used in pregnancy or in children under eight because it can affect developing teeth and bone, and it increases sun sensitivity.

Mefloquine. A weekly tablet that acts on blood-stage parasites. Its convenience is offset by a US boxed warning, added in 2013, for neuropsychiatric side effects that can persist after the drug is stopped. It is not prescribed to people with a history of depression, anxiety disorders, psychosis or seizures.

Tafenoquine (Arakoda). Approved for prophylaxis in 2018, this weekly medicine acts on both liver and blood stages and also eliminates the dormant hypnozoites of P. vivax. It requires a blood test for G6PD deficiency, an inherited enzyme shortage that makes red blood cells fragile, because in affected people it can trigger serious hemolysis. It is not approved for children or during pregnancy.

Chloroquine and hydroxychloroquine. Once the global standard, these weekly medicines are now useful only in the shrinking parts of the world where the parasite remains sensitive, chiefly parts of Central America and the island of Hispaniola.

Primaquine. A daily option sometimes chosen for areas where P. vivax dominates. It also requires G6PD testing.

Malaria prophylaxis comparison: how the main options differ

Laid side by side, the differences are mostly about frequency, how long you keep taking the medicine after you leave, and who should avoid it. The table below summarizes the mainstream guidance from the CDC and NHS; specific regimens are set by the prescribing clinician.

Medicine	Frequency	Stage targeted	Continue after leaving risk area	Notable cautions
Atovaquone-proguanil	Daily	Liver and blood (causal)	About one week	Severe kidney disease; pregnancy; take with food
Doxycycline	Daily	Blood (suppressive)	About four weeks	Pregnancy; children under eight; sun sensitivity; esophageal irritation
Mefloquine	Weekly	Blood (suppressive)	About four weeks	Psychiatric history; seizures; some heart rhythm problems; boxed warning
Tafenoquine	Weekly after a short loading period	Liver, blood and dormant forms	About one week	Requires G6PD test; not for children or pregnancy; psychiatric history
Chloroquine	Weekly	Blood (suppressive)	About four weeks	Only where parasites remain sensitive; retinal effects with very long use
Primaquine	Daily	Liver and dormant forms	About one week	Requires G6PD test; not in pregnancy

Two patterns jump out. First, the daily medicines are less forgiving of a missed day but shorter in their post-travel tail, while the weekly ones are easier to remember but stretch a full month beyond the trip. Second, every medicine has at least one group of people who should not take it, which is why an off-the-shelf choice without a medical history is a poor idea.

What the table cannot capture is the destination. A trip to rural Papua New Guinea, where P. vivax is common, raises different questions from a safari in Tanzania, where almost all malaria is P. falciparum. Mefloquine resistance in parts of the Thai-Cambodian border region rules that drug out for some itineraries entirely.

When to start malaria tablets and why timing matters

The single most common mistake clinicians see is not choosing the wrong medicine. It is starting late and stopping early.

Starting ahead of travel serves two purposes. The practical one is to reach a protective level in the blood before the first bite. The daily medicines achieve this within a day or two, which is why they suit last-minute travelers. The weekly medicines take longer, and mefloquine in particular is usually begun two to three weeks ahead. The second purpose is a tolerance test. If a medicine is going to cause vivid dreams, dizziness or stomach upset, it is far better to discover that at home, where switching is simple, than in a rural guesthouse without a pharmacy.

During travel, consistency matters more than perfection. Daily medicines should be taken at roughly the same time, with food where recommended, and a single missed dose is generally made up as soon as it is remembered rather than doubled. Vomiting shortly after a dose can mean it was not absorbed, and travelers should ask their clinician in advance what to do in that situation.

The post-travel tail is where discipline collapses. People get home, feel fine, and the remaining tablets end up in a drawer. Yet the parasite’s liver stage can last up to two weeks, and occasionally longer for P. vivax, so a bite on the last night of a trip can produce bloodstream parasites after the traveler is back at work. The suppressive medicines exist to catch exactly those parasites, which is why they continue for about four weeks. Stopping at one week with doxycycline or mefloquine is roughly equivalent to not having taken the second half of the trip’s protection.

Symptoms of malaria typically appear 7–30 days after an infective bite, though P. vivax and P. ovale can relapse months later. That window is the practical reason any fever within a year of travel to a malaria area is treated as malaria until proven otherwise.

What the evidence actually says about malaria prophylaxis

Confidence in this field rests on a mix of randomized trials, large observational surveillance programs and decades of pharmacology, and the strength varies by question.

Does prophylaxis work? Strong evidence. Placebo-controlled randomized trials conducted in non-immune volunteers and in military populations in the 1990s and 2000s showed protective efficacy well above 90 percent for atovaquone-proguanil, doxycycline and mefloquine when taken as directed. Tafenoquine’s approval rested on randomized trials in Australian soldiers and healthy volunteers with similar protection. These are the kinds of studies that make the recommendation grade high across the CDC, WHO and NHS.

Which is best tolerated? Moderate to strong evidence. A systematic review of randomized trials pooling more than 20,000 travelers found that people taking mefloquine were more likely to stop the medicine because of side effects than those taking atovaquone-proguanil or doxycycline, mainly because of abnormal dreams, insomnia, anxiety and depressed mood. Serious psychiatric harm was uncommon in trials, but the US boxed warning reflects post-marketing reports of persistent symptoms, which is observational rather than trial-level evidence.

Does non-adherence drive imported malaria? Strong observational evidence. CDC surveillance of imported cases consistently finds that the majority of US travelers who develop malaria either took no prophylaxis or did not complete the regimen. That is a correlation from case reports, not a trial, but it is a very consistent one.

Do repellents and nets substitute for medicine? Evidence does not support substitution. Insecticide-treated nets reduce malaria in endemic communities, a finding backed by randomized trials. Repellents reduce bites. Neither has been shown in travelers to match the protection of medicine, and guidelines treat them as additions, not replacements.

Natural alternatives? No evidence. There are no controlled trials showing that garlic, thiamine, tonic water or essential oils prevent malaria in humans. Expert opinion on these is uniform, and negative.

Malaria tablets side effects: what is common, what is rare

Most people take antimalarials without serious trouble. Knowing the likely minor effects in advance makes it easier to persist, and knowing the rare serious ones makes it easier to recognize when to stop and seek help.

Atovaquone-proguanil most often causes mild stomach upset, headache or mouth ulcers. Taking it with food or milk reduces nausea and improves absorption. Serious reactions are rare.

Doxycycline is best known for photosensitivity, an exaggerated sunburn response that can appear after minutes outdoors. It can also irritate the esophagus if it lodges in the throat, which is why it is taken with a full glass of water while upright. Some women notice an increased tendency to vaginal yeast infections. Rarely, it raises pressure inside the skull, producing persistent headache and visual disturbance.

Mefloquine commonly produces vivid or unpleasant dreams, trouble sleeping and dizziness. Less commonly it causes anxiety, low mood or confusion. The US Food and Drug Administration’s boxed warning notes that neuropsychiatric effects can continue for months or years after stopping in a small number of people. Any psychiatric symptom on mefloquine is a reason to contact the prescriber promptly.

Tafenoquine shares the dream and sleep effects of mefloquine to a milder degree and can cause headache, stomach upset and a reversible darkening of the cornea seen on eye examination. Its serious risk, hemolytic anemia, is confined almost entirely to people with G6PD deficiency, which is why testing before the first dose is mandatory rather than optional.

Chloroquine may cause itching, especially in people of African descent, along with nausea and blurred vision. Retinal damage is a concern only with years of continuous use.

A useful rule: nuisance effects that appear in the first week often settle; new neurological, psychiatric, visual or allergic symptoms at any point deserve a same-day call to the clinician.

Who needs special care: pregnancy, children, long trips and G6PD

The standard menu shrinks quickly for several groups, and in each case the stakes rise rather than fall.

Pregnancy. Malaria in pregnancy is more severe for the mother and raises the risk of miscarriage, stillbirth and low birth weight. The CDC and NHS advise pregnant travelers to avoid malaria areas where possible. If travel is unavoidable, chloroquine is used where it still works, and mefloquine is the option with the most reassuring safety data in regions of chloroquine resistance. Doxycycline, primaquine and tafenoquine are avoided, and atovaquone-proguanil is generally not recommended because of limited data. Breastfeeding adds further constraints, particularly because the infant’s G6PD status matters for some drugs.

Children. Young children develop severe malaria faster than adults. Atovaquone-proguanil and mefloquine can be used in children with weight-based prescribing; doxycycline is avoided under eight and tafenoquine is not approved for pediatric prophylaxis. Tablets often need to be crushed and disguised in food, which parents should plan for.

Long-term travelers and expatriates. People staying months or years sometimes stop prophylaxis out of fatigue or local advice. Guidelines support long-term use of atovaquone-proguanil, doxycycline and mefloquine where needed, and there is no requirement to take breaks for most healthy adults. The decision is individualized.

G6PD deficiency. This inherited enzyme shortage affects roughly 400 million people worldwide, most commonly those with African, Mediterranean, Middle Eastern and South or Southeast Asian ancestry. Primaquine and tafenoquine can cause red blood cells to break down in affected people, so a quantitative G6PD blood test is required before either is prescribed.

Other conditions. Kidney disease, epilepsy, heart rhythm disorders, psychiatric history and medicines such as anticoagulants or anticonvulsants each narrow the options. None of this makes prophylaxis impossible; it makes the consultation essential.

Do I need malaria tablets if I grew up in a malaria country?

This is the question travel clinics hear most from people visiting friends and relatives, and the answer is almost always yes.

People who grow up in high-transmission areas do develop partial immunity, but it is a narrow, hard-won protection built by repeated infections over years. It does not prevent infection; it blunts the severity of symptoms. And it fades. Within a year or two of moving to a country without malaria, the immune memory that kept symptoms mild begins to wane, and after several years an adult returning home is, from the parasite’s point of view, close to a first-time visitor.

The surveillance data reflect this. In CDC reports on imported malaria, travelers visiting friends and relatives consistently account for the largest share of cases, and a disproportionate share of severe cases. They tend to stay longer, sleep in family homes without screens or air-conditioning, visit rural areas and, crucially, are the least likely to seek pre-travel advice or take prophylaxis. Many assume they are still immune. Others were told by relatives that the medicine is unnecessary or harmful.

Children born abroad to parents from endemic countries deserve particular attention. They have no acquired immunity at all, and a family trip to a grandparent’s village exposes them to exactly the same risk as any other non-immune child.

The same logic applies to people who took a single trip years ago without incident. Not catching malaria once is luck, not protection. Transmission intensity varies by season, by village and by year, and a dry-season visit that went smoothly says little about a rainy-season return.

The decision about whether a particular itinerary warrants prophylaxis, and which medicine fits, belongs with a clinician who can check current destination risk. For most travel to sub-Saharan Africa, the guidance from the CDC, WHO and NHS is unambiguous: prophylaxis is recommended for everyone, regardless of birthplace.

Beyond the pills: bite prevention and the malaria vaccines

Medicine is the main layer of protection for travelers, but it is not the only one, and the other layers are not optional extras.

Anopheles mosquitoes bite mostly between dusk and dawn, so evening and overnight behavior matters most. The CDC and NHS recommend repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus, applied to exposed skin after sunscreen. Long sleeves and trousers in light colors reduce the exposed surface. Clothing and gear can be treated with permethrin, an insecticide that stays active through several washes. Where accommodation is not sealed and air-conditioned, sleeping under an insecticide-treated bed net tucked beneath the mattress is the intervention with the strongest trial evidence in endemic communities.

These measures also protect against dengue, chikungunya and Zika, carried by daytime-biting Aedes mosquitoes, against which there is no routine travel medicine.

Then there are the vaccines. Two have WHO recommendations: RTS,S/AS01, recommended in 2021, and R21/Matrix-M, recommended in 2023. Both target the sporozoite stage of P. falciparum and both are recommended by the WHO for children living in areas of moderate to high transmission, given in a multi-dose series starting in infancy. In trials they reduced clinical malaria episodes substantially during the first year, with protection that waned without boosters. They are being delivered through national childhood immunization programs in a growing number of African countries.

What they are not is a travel vaccine. Neither is licensed for adults, neither is approved in the United States or the United Kingdom, and neither is recommended by the CDC, WHO or NHS for visitors. Several candidate vaccines for travelers are in clinical trials, but as of 2025 they remain investigational and are not available for use outside those studies. For now, a traveler’s protection remains prophylaxis plus bite prevention, nothing less.

Common myths about malaria prophylaxis, corrected

The claims below circulate widely enough that most travel clinics have a prepared answer for each.

Myth: Repellent and a net are enough. They reduce bites, and nets have strong trial evidence in endemic populations. They have never been shown to protect non-immune travelers as well as medicine, and guidelines treat them as an addition to prophylaxis, not a replacement.

Myth: Vitamin B1, garlic or tonic water keep mosquitoes away or kill the parasite. No controlled study supports any of these. Modern tonic water contains far too little quinine to have any antimalarial effect.

Myth: Antimalarials stop working if you take them too often. Drug resistance develops in parasite populations under treatment pressure in endemic areas, not in an individual traveler who takes prophylaxis for several trips.

Myth: The tablets mask malaria so doctors cannot diagnose it. Prophylaxis can delay symptoms or make them milder, which is a reason to mention it to any clinician assessing a fever, not a reason to skip it. Blood tests still detect the parasite.

Myth: All antimalarials cause psychiatric problems. The neuropsychiatric warning applies specifically to mefloquine, and to a lesser degree tafenoquine. Atovaquone-proguanil and doxycycline do not carry that profile.

Myth: If you did not get malaria last time, you do not need it this time. Transmission varies by season and location; a previous uneventful trip is not evidence of immunity.

Myth: Chloroquine works everywhere. It works in a handful of regions. Across Africa and most of Asia the parasite has been resistant to it for decades.

Myth: You can start the tablets when you arrive and stop when you leave. Starting ahead builds protection and tests tolerance; continuing afterward covers parasites still maturing in the liver. Both ends of the schedule are part of the medicine.

When to see a doctor: red flags during and after travel

Malaria can progress from a vague fever to a medical emergency within 24 to 48 hours, especially with P. falciparum. The threshold for seeking care should be low, and the message to the clinician should be explicit: I have been in a malaria area.

Before travel, see a clinician ideally four to six weeks ahead, though even a visit the day before departure is far better than none. Bring a list of medicines, medical conditions, pregnancy or breastfeeding status, and the full itinerary including rural stops.

During travel, seek medical attention the same day for:

• Fever, chills, sweats or flu-like illness, with or without headache and muscle aches
• Severe vomiting that prevents keeping tablets down
• New confusion, agitation, hallucinations, severe anxiety or depressed mood, particularly on mefloquine or tafenoquine
• Dark urine, yellowing of the eyes or unusual breathlessness, which can signal red cell breakdown
• Rash, facial swelling or difficulty breathing suggesting an allergic reaction

After travel, treat any fever within a year of leaving a malaria area, and particularly within the first three months, as malaria until a blood test proves otherwise. Tell the emergency department or urgent care about the travel immediately; it changes the testing they order.

Call emergency services for drowsiness or difficulty waking, seizures, severe breathing difficulty, very little urine, or a fever in a young child or pregnant woman after travel.

Do not stop a prescribed antimalarial on your own because of side effects, and do not switch to a medicine bought abroad without medical advice. Counterfeit antimalarials are common in some regions. Every decision about continuing, changing or stopping prophylaxis belongs with the prescribing clinician, who can weigh the symptom against the risk of leaving you unprotected.

Is there a best antimalarial for travel? How to prepare for the consultation

There is no single best antimalarial for travel, and anyone who tells you otherwise is answering a different question from the one that matters, which is: what is best for this person, on this trip, right now.

That said, the choice usually follows a recognizable logic. For a short trip of a week or two, a daily causal medicine such as atovaquone-proguanil is often favored because it starts quickly and ends within a week of return. For a long stay, cost and convenience shift the calculation toward a weekly option or doxycycline, provided the traveler’s history allows. For destinations where P. vivax is common, a medicine that also clears dormant liver forms may appeal, which brings G6PD testing into the picture. For the parts of Southeast Asia with mefloquine resistance, that drug is simply off the table.

The most useful thing you can do is make the clinician’s job easy. Arrive with the itinerary written down, including stopovers, rural overnights and dates. Know your medical history, especially any psychiatric diagnosis, seizures, kidney disease or heart rhythm problems. Bring a list of current medicines, including contraceptives, anticoagulants and supplements, because antimalarials interact with several. Mention pregnancy, plans to conceive or breastfeeding. Say honestly how good you are at remembering a daily tablet; that single answer often decides between a daily and a weekly medicine.

Ask three questions before you leave the room. What exactly do I do if I miss a dose or vomit after one? Which side effects should make me call you, and which can I ride out? And what should I say to a doctor if I develop a fever after I get home?

Done well, malaria prophylaxis is one of the quieter success stories in travel medicine: a decades-old set of medicines that, taken on schedule, protect more than nine in ten travelers from a disease that still kills hundreds of thousands of people every year. The pills do the biology. The calendar is up to you.

Frequently asked questions

When should I start malaria tablets before a trip?

It depends on the medicine, which is why a travel consultation ideally happens four to six weeks before departure. Daily medicines such as atovaquone-proguanil and doxycycline reach protective levels within a day or two, so they suit last-minute travel. Weekly medicines, especially mefloquine, are usually begun two to three weeks ahead, partly to build levels and partly to check tolerance at home.

What are the most common malaria tablets side effects?

Mild stomach upset and headache are the most frequent across all options. Doxycycline adds sun sensitivity and throat irritation; mefloquine is known for vivid dreams, insomnia and dizziness, with a boxed warning for psychiatric effects; tafenoquine can cause mild sleep changes and requires G6PD testing to avoid hemolysis. New neurological, psychiatric, visual or allergic symptoms warrant a same-day call to the prescriber.

Do I need malaria tablets for a city-only trip?

Sometimes, and the answer is destination-specific. Many large cities in Asia and Latin America carry little or no malaria risk, while most cities in sub-Saharan Africa do. The CDC Yellow Book lists risk at the regional and city level, and a travel clinician will use it alongside your exact itinerary, length of stay and accommodation to decide whether prophylaxis is recommended.

Is there a best antimalarial for travel to Africa?

No single medicine is best for everyone. For most of sub-Saharan Africa, where chloroquine resistance is universal, the options are atovaquone-proguanil, doxycycline, mefloquine and tafenoquine. The choice turns on trip length, medical history, pregnancy, age, other medicines and how reliably you can take a daily tablet. The prescribing clinician makes that call.

Can I prevent malaria without tablets by using repellent and a net?

Not reliably. Insecticide-treated nets reduce malaria in endemic communities, and repellents reduce bites, but neither has been shown to protect non-immune travelers as well as medicine. The CDC, WHO and NHS recommend bite prevention in addition to prophylaxis, never as a substitute, for travel to areas where chemoprophylaxis is advised.

Why do some malaria tablets continue for four weeks after travel?

Because they act only on parasites in the blood. Malaria parasites spend one to two weeks, occasionally longer, multiplying silently in the liver before entering the bloodstream. Suppressive drugs such as doxycycline, mefloquine and chloroquine must still be present when those parasites emerge. Causal drugs that kill the liver stage, like atovaquone-proguanil, can stop sooner.

Is there a malaria vaccine for travelers?

Not at present. The WHO recommends two vaccines, RTS,S/AS01 and R21/Matrix-M, for children living in areas of moderate to high malaria transmission, given through national immunization programs. Neither is licensed for adults or approved in the United States or United Kingdom, and neither is recommended for travelers. Candidate travel vaccines remain investigational and are not available outside clinical trials.

What is G6PD deficiency and why does it matter for malaria prophylaxis?

G6PD deficiency is an inherited shortage of an enzyme that protects red blood cells from oxidative damage. In affected people, primaquine and tafenoquine can cause red cells to break down rapidly, leading to hemolytic anemia. A quantitative G6PD blood test is therefore required before either medicine is prescribed. The other antimalarials do not carry this risk.

I grew up in a malaria country. Am I still immune?

Almost certainly not to a useful degree. Immunity acquired through repeated childhood infections only reduces symptom severity and fades within a few years of living somewhere without malaria. Travelers visiting friends and relatives make up the largest group of imported cases in the United States and have a higher rate of severe disease, so prophylaxis is recommended regardless of birthplace.

What should I do if I get a fever after coming home?

Seek medical care the same day and state clearly that you have traveled to a malaria area, including dates. Fever within a year of travel, and especially within three months, should be treated as malaria until a blood test rules it out. Falciparum malaria can become life-threatening within 24 to 48 hours, so do not wait to see whether the fever settles.

References

• World Health Organization: Malaria fact sheet
• NHS: Malaria
• MedlinePlus: Malaria

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.