The hepatitis B vaccine is given at birth primarily to prevent newborns from acquiring the hepatitis B virus (HBV) during birth, especially from an infected mother. If a baby catches hepatitis B at birth, there is about a 90% chance they will develop chronic hepatitis B, which can lead to serious lifelong liver diseases such as cirrhosis and liver cancer. Giving the vaccine within 24 hours of birth significantly reduces the risk of infection and protects infants until subsequent doses are given in the following months. This early vaccination helps prevent both perinatal transmission (from mother to child during delivery) and horizontal transmission (from close contacts). It is a critical safety measure especially because many adults with hepatitis B may be unaware they carry the virus. Vaccinating at birth has been shown to greatly reduce the incidence of chronic hepatitis B infection and its severe long-term consequences.
