Many people have already learned about mRNA vaccines, and may remember that when they were first approved by the FDA and CDC they had ~97% efficacy at protecting from infection. So what happened? Why did we need boosters last year and what is an Updated (aka Bivalent) booster?
The original efficacy of the vaccine speaks to how well the vaccines worked at protecting individuals from infection with the initial variants of COVID-19. Since the end of 2020, SARS-CoV-2 (the virus responsible for causing COVID-19) has shown to be one of the most mutagenic viruses ever studied. This means the virus has mutated into various Variants of Concern (VOC) since the original vaccines were manufactured.
These VOC’s have since evolved to evade the immunity provided both by prior infection with COVID-19 and vaccination. These mutations have caused a drop in efficacy of the original mRNA vaccines. Booster doses of the original formulation were approved last year and helped ‘remind’ your immune system how to defend against COVID-19. However, since these vaccines still targeted the original strain of SARS-CoV-2, they did not provide the immune system with any new tools in order to fend off infection.
Enter Updated Boosters. In June of 2022, the FDA chose to update the mRNA formulation in order to provide protection against the BA.4 and BA.5 strains of SARS-CoV-2. If the immune response is our first line of defense against infection, akin to a locked door, think of the new updated boosters as changing the locks after COVID-19 copied our previous keys (immune evasion). The updated boosters are specifically formulated to provide high levels of protection against the current circulating VOC’s by providing your immune system with an updated set of tools.
This winter it is particularly difficult to predict what will happen with COVID-19 due to a dramatic reduction globally in testing and genetic sequencing. Currently it looks like a winter wave may be made up of XBB or BQ.1.1 VOC’s. Both of these variants are the most mutated and most immune evasive we have seen to date. This means that even if you have been vaccinated or had prior infection, you could become infected with these variants. Fortunately for us, Updated Boosters have been formulated with the parent lineages to both of these VOC’s; meaning they will likely provide high levels of protection.
While we know that the virus will continue to mutate to evade our current defenses, thus causing lower vaccine efficacy over time, the mRNA vaccine technology allows us to quickly update the formulation when new VOC’s evolve. We will likely see yearly or seasonally updated COVID-19 vaccinations similar to flu vaccines.
The best way to protect yourself from contracting COVID-19 and reduce your risk of suffering severe negative outcomes due to infection or even Long COVID, is to get vaccinated with an Updated Booster dose of either Modern or Pfizer. Remember, it takes 2 weeks for your body to build an immune response after vaccination and protection typically lasts 3-6 months, so in order to be fully protected by the Holiday Season and throughout the winter you should get vaccinated as soon as possible. Dates for upcoming vaccination clinics in the RFV can be found here.
