A common argument against COVID-19 vaccination is “Surely the vaccines can’t be effective if I require a booster?”

All vaccines work to train the immune system to recognise foreign invaders and produce antibodies that will attack them. But the strength of the initial immune response, and the amount of time the antibodies will last, varies depending on both the pathogen the vaccine is fighting, and the vaccine itself. Measles antibodies, for example, are long lasting, which is why only children get the jab.

Added to the complexities of how long antibodies last, is the extent to which a virus can mutate. And we know that COVID is a master of mutation! A rapidly evolving virus can trick a trained immune system and cause illness by changing its appearance or finding new ways to attack. Trying to create a vaccine to detect every new mutation is like trying to hit a moving target… tricky, but not impossible. COVID-19 is not the first virus to do this… and that is why there is a new flu vaccine released each year.

Vaccines do more than just help the immune system to produce antibodies. Vaccines educate the entire immune system, including T-cells, a type of white blood cell involved in removing pathogens from the body. There is growing evidence that even though COVID-19 variants may evade vaccine-induced antibodies, other aspects of a vaccine-boosted immune system, including T cells, are not as easily fooled!

The current evidence available suggests that while there is a waning immune response from the initial COVID-19 vaccine doses, those who have a booster dose have superior protection against severe disease. In other words, a third dose simply tops up the immune response, supercharging it’s potential to fight off whatever mutation it may have to face next.

References:

• Duration of Protection against Mild and Severe Disease by Covid-19 Vaccines. N Engl J Med 2022; 386:340-350
• The Harvard Gazette. Breaking down boosters
• National Institute of Communicable Diseases. COVID-19 Booster Shot FAQs