The innate and the acquired immune systems combat viral infections. The former is infection type independent. The latter is infection type dependent and takes several days to be “educated” as to the, for example, specific viral infection. With that, B and T lymphocytes are activated. B lymphocytes make specific antibody, which is readily measured, while T lymphocyte functions are not so easily measured.

Specific antibody is measured to indicate that a specific infection has occurred. Antibody (monoclonal or polyclonal) may also be used to treat individuals. Such antibody-treated individuals are passively immunized, which is short lasting as compared with more long-lasting active immunity. The latter is achieved by recovery from infection or vaccine immunization.

Immunization with vaccines has been very important in public health. New types of vaccines have been developed, with recent emphasis particularly on mRNA vaccines. These can be made much more quickly than prior types of vaccines. They target a specific viral protein (antigen) and may find use in other types of illnesses where a specific abnormal protein is identified.

While side effects may occur with vaccines, as is the case with all medications, they are very safe.