Revaccination

Revaccination (from Latin re- — renewal, repetition, and vaccinus — bovine) is the repeated administration of a vaccine antigen to a person who has previously completed the full course of primary immunization.

The purpose of this procedure is to restore or enhance acquired immunity, which comprises a natural tendency to wane over time.

Etiology and pathophysiology

Following successful primary vaccination, a pool of immunological memory cells (T and B lymphocytes) is formed in the body.

However, if the immune system does not encounter the actual wild-type virus or bacterium for years, the number of circulating protective antibodies and specific cells gradually declines to a critically low level (the phenomenon of waning immunity).

Revaccination acts as a “reminder.” Repeated administration of the antigen results in the immediate activation of dormant memory cells.

A secondary immune response develops: rapid synthesis of IgG antibodies occurs.

Clinical significance

The concept of revaccination underlies the National Immunization Schedule for children and adults in many countries. In medical practice, several principal indications for the use of booster doses are recognized:

• against diphtheria and tetanus — immunity is not lifelong; therefore, adults require regular revaccination every 10 years;
• against certain infections (for example, pertussis) — revaccination is important during adolescence and adulthood because the protection conferred by childhood vaccination wanes after 3–5 years;
• to protect against viruses prone to rapid mutation (for example, coronavirus) — booster doses are administered to maintain protection. In this case, revaccination not only increases the overall antibody titer but also “updates” the immune database by exposing the body to new strains of the pathogen.