What is the active component in the Boostrix vaccine?

The active component in the Boostrix vaccine is Bordetella pertussis antigen. Boostrix is a combination vaccine that provides protection against three diseases: tetanus, diphtheria, and pertussis (whooping cough). The inclusion of Bordetella pertussis antigen specifically helps stimulate the immune system to recognize and fight the bacteria that cause whooping cough. This antigen prompts the body to produce antibodies against Bordetella pertussis, thus offering immunity.

In this context, the other options do not match the components of the Boostrix vaccine. Tetanus toxoid is included in the vaccine, but it is not the primary active component that defines it. The influenza virus and measles virus options pertain to entirely different vaccines that protect against their respective diseases and are not related to Boostrix. Understanding the specific components of vaccines is crucial for recognizing their intended protective effects and the rationale behind combining different antigens in an immunization strategy.