Hepatitis A is a vaccine-preventable viral liver infection caused by the hepatitis A virus (HAV), spread through contaminated food and water and through close contact with an infected person. WHO estimates roughly 1.5 million clinical cases of hepatitis A globally each year, with much higher unreported infection rates and the heaviest burden in regions with limited safe-water and sanitation infrastructure. Travelers from low-incidence countries to high-endemicity areas are a recurring source of US imported cases.

The vaccine works extraordinarily well. A single dose gives roughly 95% protection within 2 to 4 weeks, and the two-dose series provides protection for at least 25 years and likely lifelong. Despite that, US adults born before universal childhood vaccination (introduced in 2006) often remain unvaccinated, and most travel-associated US hepatitis A cases occur in adults who never got around to getting the shot. Hepatitis A vaccination is one of the highest-yield items in any pre-departure plan, and our outbreak-aware travel guide covers how it fits alongside food-and-water rules, vaccinations, and destination-specific risk research.

Key Takeaways

What is hepatitis A and where is it endemic?

Hepatitis A is a vaccine-preventable viral infection of the liver caused by HAV. WHO categorizes countries by endemicity, with the highest rates in parts of sub-Saharan Africa, South Asia, the Middle East, and Central and South America. Most US travel-associated cases come from Mexico, Central America, and South Asia. CDC's traveler health pages list current vaccine recommendations by destination.

Endemicity correlates with sanitation infrastructure. In high-endemicity regions, most people are exposed in early childhood and develop lifelong immunity, often without recognizing the infection. In low-endemicity countries with universal childhood vaccination, most adults under 20 are protected through the routine schedule, but adults over 30 who never traveled or boosted may have no immunity at all.

Outbreaks in the US most often involve restaurant food handlers, contaminated produce or shellfish, and person-to-person spread among populations with limited sanitation access. Recent multi-state outbreaks have been linked to imported strawberries, raw oysters, and salad blends. Our foodborne disease outbreaks post covers the broader food-traceback picture.

How does hepatitis A spread to travelers?

Hepatitis A spreads almost entirely through fecal-oral routes: contaminated water and food (especially raw shellfish, salads, ice, and unpeeled fruit washed in unsafe water), contaminated cooking and serving utensils, and close personal contact with an infected person. Travelers most often become infected from food or beverages prepared by an asymptomatic shedder or through contaminated water sources.

The incubation period averages 28 days, which means the exposure usually happened 3 to 6 weeks before symptoms appear. By the time you get sick, you may be back home and unable to recall what you ate where. CDC's outbreak investigations frequently identify the source weeks after the patient's return, which is part of why travel vaccination matters.

Cooking inactivates HAV at sustained temperatures above 85°C for at least 1 minute. Freezing does not. Bottled water, peeled-by-you fruit, and food served hot all-the-way-through are the standard travelers' precautions. The travelers' diarrhea post covers the same food-and-water rules in more depth.

How effective is the hepatitis A vaccine and when should you get it?

A single dose of hepatitis A vaccine provides roughly 95% protection within 2 to 4 weeks of administration. CDC recommends the first dose at least 2 weeks before travel, though even last-minute doses provide useful protection by departure. The second dose is given 6 months later and confers protection for at least 25 years, likely lifelong, per CDC.

Two vaccines are available in the US: Havrix and Vaqta. Both are inactivated whole-virus vaccines, both are highly immunogenic, and they are interchangeable. The combination Twinrix vaccine covers hepatitis A and hepatitis B in a 3-dose schedule and is useful when travel pre-departure timing allows or when both vaccines are indicated.

For very late travelers (under 2 weeks before departure), CDC allows giving the vaccine plus immune globulin if the traveler is over 40, immunocompromised, or has chronic liver disease. The travel vaccinations timing guide covers the broader pre-departure schedule for hepatitis A alongside other common travel vaccines.

What food and water precautions reduce risk?

Drink only sealed bottled water or water boiled for 1 minute (3 minutes above 2,000 m elevation), avoid ice unless made from safe water, eat only fruit you peel yourself, eat hot foods that are still hot through the center, and avoid raw or undercooked shellfish entirely. These rules reduce hepatitis A risk and most other foodborne pathogens at the same time.

Lettuce and salad greens are a recurring problem because washing in contaminated water can recontaminate them faster than cooking can sterilize. Avoid leafy salads and pre-cut fruit at any establishment where you cannot trust the water source. Sealed commercial yogurt and dairy products are generally safe in countries with reliable cold chains, but raw dairy is not.

Hand washing with soap and water before eating and after using the bathroom is the single most useful traveler behavior beyond the vaccine itself. CDC's traveler hand-hygiene guidance applies in any setting where you wouldn't drink the tap water, and our hand hygiene technique guide goes through the technique in detail.

What if you've been exposed and not vaccinated?

CDC recommends post-exposure prophylaxis (PEP) within 14 days of exposure to hepatitis A. For healthy people aged 12 months to 40 years, a single dose of hepatitis A vaccine is preferred. For adults over 40, immunocompromised people, those with chronic liver disease, and people whose vaccination would be contraindicated, immune globulin (IG) is used instead, sometimes with simultaneous vaccine.

PEP works best when given as early as possible. Effectiveness drops as the 14-day window closes and is minimal beyond it. Health departments contact-trace confirmed hepatitis A cases and notify exposed individuals, which is the usual mechanism for getting PEP. Travelers returning with possible exposure should contact their physician early rather than waiting for symptoms.

If you develop symptoms (fatigue, nausea, abdominal pain, jaundice, dark urine) within 50 days of travel to an endemic area, see a physician promptly and mention the travel history. Hepatitis A is reportable in all 50 states, which lets the local health department investigate and prevent secondary cases through PEP for close contacts.

FAQ

Do I need a hepatitis A vaccine for Mexico?

CDC's traveler health page lists hepatitis A vaccination as recommended for nearly all travelers to Mexico, regardless of length of stay or accommodation type. The recommendation also covers Central America, South America, parts of the Caribbean, most of Africa, and most of South and Southeast Asia. Specific destinations and risk levels are updated annually on CDC's traveler pages.

How quickly does the hepatitis A vaccine protect you?

Roughly 95% of healthy adults develop protective antibody levels within 2 to 4 weeks of a single dose. CDC's official recommendation is to get the first dose at least 2 weeks before departure, but even doses given right before travel provide some protection because the virus has a long incubation period of 15 to 50 days.

Is hepatitis A the same as hepatitis B or C?

No. The three are separate viruses with different transmission routes and clinical courses. Hepatitis A is a fecal-oral RNA virus that causes acute illness and rarely chronic infection. Hepatitis B is a DNA virus spread through blood and body fluids that can become chronic. Hepatitis C is an RNA virus spread mostly through blood that frequently becomes chronic. Vaccines exist for A and B but not C.

Can hepatitis A become chronic?

No. Hepatitis A causes only acute infection. Recovery confers lifelong immunity. The infection can occasionally relapse over 6 to 12 months, and rare cases of severe acute liver failure occur (mostly in older adults and people with chronic liver disease), but it does not establish chronic infection like hepatitis B or C.

What does hepatitis A look like clinically?

Symptoms appear 15 to 50 days after exposure and include fatigue, nausea, vomiting, abdominal pain (especially in the right upper quadrant), low-grade fever, dark urine, pale stools, and jaundice (yellowing of skin and eyes). Children under 6 are often asymptomatic. Most adults are sick for 2 to 6 weeks, with full recovery within 2 to 6 months.