The hepatitis D (or Delta) virus only affects people who are already infected with hepatitis B, as it needs the hepatitis B virus to be able to survive in the body. Coinfection with HBV and HDV results in more severe complications than with HBV alone. The HBV vaccine protects against HDV because of the latter’s dependence on the former.
Learn more about HIV, including who’s at risk, where to get tested, and how you can prevent it.