Yes, there is a vaccine for hepatitis A, and it’s highly effective. More than 95% of adults develop protective antibodies within four weeks of a single dose, and nearly 100% are fully protected after completing the two-dose series. The vaccine has been available in the United States since the 1990s and is now part of the routine childhood immunization schedule.
Types of Hepatitis A Vaccines
Three FDA-licensed vaccines protect against hepatitis A in the United States. Two are standalone hepatitis A vaccines: Havrix and VAQTA. Both use an inactivated (killed) form of the virus, meaning they cannot cause the infection. A third option, Twinrix, combines hepatitis A and hepatitis B protection into a single shot, which can reduce the total number of injections you need if you’re due for both.
How the Vaccine Works
The hepatitis A vaccine contains virus that has been grown in cell culture, purified, and then chemically inactivated so it can no longer replicate. When injected, your immune system recognizes the dead virus particles as a threat and builds antibodies against them. An aluminum-based ingredient in the vaccine helps amplify that immune response. If you’re ever exposed to the live virus afterward, your body already has the antibodies ready to neutralize it before it can establish an infection.
Dosing Schedule for Children and Adults
Children receive their first dose between 12 and 23 months of age, followed by a second dose at least six months later. Adults who were never vaccinated as children can get the same two-dose series at any age, with the same six-month minimum gap between shots.
If you need protection against both hepatitis A and hepatitis B, the combination vaccine (Twinrix) follows a different timeline. On the standard schedule, you get three doses: the second at least one month after the first, and the third at least six months after the first. There’s also an accelerated four-dose schedule for situations like upcoming travel, where the first three doses are given over about three weeks and a booster follows at 12 months.
How Well It Works and How Long It Lasts
The hepatitis A vaccine is one of the most effective vaccines available. A single dose protects more than 95% of healthy adults within four weeks. The second dose pushes that number to nearly 100% and is what locks in long-term immunity. Studies tracking vaccinated individuals over decades suggest protection lasts at least 25 years and possibly a lifetime, though researchers are still monitoring this. No booster doses are currently recommended after completing the initial series.
Side Effects
The most common side effects are mild and local: soreness, tenderness, pain, or warmth at the injection site. Headache is the most frequently reported systemic reaction in both adults and children. Young children (roughly 11 to 25 months old) may also experience irritability, drowsiness, or loss of appetite. These side effects typically resolve within one to two days. Serious reactions are rare.
Who Should Get Vaccinated
All children should receive the vaccine starting at age one. Beyond that, several groups of adults face higher exposure risk and should prioritize vaccination:
- International travelers, particularly to countries where hepatitis A is common
- Men who have sex with men
- People who use or inject drugs
- People whose jobs put them at risk of exposure
- People expecting close contact with an international adoptee
- People experiencing homelessness
Some people also face a higher risk of serious illness if they do get infected, making vaccination especially important. This includes people with chronic liver disease (including hepatitis B or C), people living with HIV, and pregnant women. Hepatitis A is rarely fatal in healthy adults, but it can cause severe or prolonged liver damage in people whose livers are already compromised.
Protection After Exposure
The vaccine can also work as emergency protection after you’ve already been exposed to the virus. If you receive a dose within two weeks of exposure, it can prevent the infection from taking hold. This post-exposure use applies to anyone 12 months or older who hasn’t already completed the full vaccine series. The key is speed: the sooner you get the shot after exposure, the better it works. After the 14-day window, the vaccine is far less likely to prevent that particular infection, though it still protects against future exposures.
Who Should Not Get the Vaccine
Very few people have a reason to skip the hepatitis A vaccine. The main contraindication is a previous allergic reaction to a dose of the vaccine or to any of its ingredients. For the combination vaccine Twinrix specifically, an allergy to neomycin (an antibiotic) or yeast is also a contraindication. If you’re moderately or severely ill, it’s best to wait until you recover before getting vaccinated, but a minor cold or similar illness is not a reason to delay.