Active immunity - vaccinations

A vaccination is the injection of dead or modified microorganisms.

A man getting an injection

The body’s lymphocytes produce antibodies in response to the antigens present in the vaccine.

Memory lymphocytes will also be produced – this is the primary response.

If this microorganism is encountered after the vaccine, the memory lymphocytes will produce large numbers of the antibody very quickly.

The individual does not get sick – this is the secondary response.

Sometimes a booster vaccination is needed to maintain the high levels of antibodies needed to provide immunity.