The FDA recently approved COVID-19 boosters for all U.S. adults. While it is not new for there to be booster dosages or multiple dosages for a vaccine, the main concern comes down to efficacy. Outside of older populations and immunocompromised populations, are COVID-19 booster shots effective for eliciting long term durable immunity against COVID-19?
To be frank, I am not sure but there are some serious considerations that need to talked about. Notice the COVID-19 vaccines are effective at reducing transmission, reducing risk of hospitalizations, and reducing risk of death from COVID-19. Nevertheless, we seem to have limited evidence suggesting all adults 18 and above would benefit from a booster shot.
The argument for booster shots mainly comes from this concept of waning immunity. There is evidence suggesting vaccine efficacy decreases across time. This can be due to a number of different factors such as…
However, the underlying issue behind the methodology of waning immunity is this focus on neutralizing antibody levels. Neutralizing antibodies are an essential component of the adaptive immune system and we know their levels correlate with COVID severity. Nevertheless, a decrease in these neutralizing antibodies does not translate to waning immunity.
As this commentary states:
From an immunological standpoint, plasma neutralising antibody titres are expected to decay eventually following vaccination, but robust and long lived plasmablast and germinal B cell responses have been shown after mRNA vaccination, and memory B cells have been shown to increase over at least six months, improve functionally, and provide cross-variant protection.
In simple terms, antibodies levels are suppose to decay eventually following vaccination as the body does not need high levels of antibodies for a disease it is not fighting. What is more important is memory B cells for COVID as they’re the cells which produce the neutralizing antibodies in the first place.
We do have evidence the mRNA vaccines increase levels of memory B cells across time. This would lead to long durable immunity against COVID-19.