When do vaccines take effect and what is the duration?

Reading time: 2 min

Antibodies can be detected 10 to 14 days after administrating a vaccine, but the body’s response is most consolidated three to six weeks later. Within this period there has already been time for more specialised antigen-recognising cells to have developed, allowing faster responses and high antibody production. In fact, in the first few days, the immune response is low in intensity and not very specific. It becomes more potent and specific with each day that passes, as more elements of the immune system get involved –  so much so that subsequent exposure to the same antigen (in the form of a booster dose) causes the immune response to be more rapid, and intense antibody production is achieved within just a few days.

How long the effect of a vaccine lasts depends on the antibodies generated (humoral immunity) and also on cellular immunity after the first vaccination. Therefore, the duration of the protection given will largely depend on the characteristics of the vaccine and its ability to stimulate the immune system. Speaking generically, we could say that due to their similarity to natural micro-organisms, attenuated vaccines have a greater capacity to stimulate the immune system and can provide lifelong immunity. On the other hand, inactivated vaccines, especially those containing a single micro-organism (or parts of it) and which are more purified, have less ability to stimulate the immune system, meaning they require more than one dose to complete the regimen and often require booster doses.

Substantiated information by:

Anna Vilella
Antoni Trilla
Marta Aldea

Published: 13 January 2022
Updated: 13 January 2022


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