Why a Hep B birth dose?

With ACIP expected to recommend getting rid of the Hepatitis B vaccine at birth and delaying it to age 4, we want to talk about why the vaccine is given at birth.

Hepatitis B (Hep B) can spread through sex, but that’s not the only way it spreads. Doctors recommend giving babies the Hep B vaccine at birth because many babies were being born to mothers who didn’t know they had the infection. Scientists believe that about 30–40% of people with long-lasting (chronic) Hep B got it either when they were born or when they were very young. Only about half of mothers with Hep B are found before they give birth.

Even today, around 25,000 babies in the U.S. are born each year to moms with Hep B. If a newborn catches it, about 90% of them will stay infected for life. This raises their chances of liver disease and liver cancer later on.

There are many reasons why mothers don’t know they have Hep B. The test for Hep B is harder to understand than some other tests. A mom might get infected after her first test during pregnancy, but before giving birth. Tests can also be wrong sometimes, showing a false “negative.” Mistakes can happen too—like ordering the wrong test, reading the results wrong, or not sharing the results clearly.

Hepatitis B can also live outside the body for up to 7 days, even in dried blood. That means it can spread in other ways, too, like through bites in daycare, dirty needles, or bandages left in public places. This doesn’t happen often, but it’s still possible.

The Hep B vaccine is very safe. The most common side effects are just soreness or pain where the shot was given. Serious side effects are extremely rare—so rare that none have been proven after millions of doses. Because the vaccine is safe, and babies can get Hep B at birth or soon after, doctors give the first dose right when a baby is born.