Will omicron-specific booster shots be more effective at combating COVID-19? 5 questions answered

On Sept. 1, 2022, the Centers for Disease Control and Prevention endorsed the use of updated COVID-19 booster shots that are specifically tailored to combat the two most prevalent omicron subvariants, BA.4 and BA.5. The decision comes just a day after the Food and Drug Administration’s emergency use authorization of the shots. The CDC’s backing will enable a full roll-out of the reformulated vaccines to begin within days.

The new booster shots – one by Moderna and another from Pfizer-BioNTech – come as more than 450 people are still dying of COVID-19 every day in the U.S.

As of Aug. 31, 2022, only 48.5% of booster-eligible people in the U.S. have received their first booster shot, and just under 34% of those eligible have received their second. These low numbers may in part be influenced by people waiting for the newer versions of the vaccines to provide better protection. But booster shots have proven to be an essential layer of protection against COVID-19.

Prakash Nagarkatti and Mitzi Nagarkatti are immunologists who study infectious disorders and how vaccines trigger different aspects of the immune system to fight infection. They weigh in on how the updated booster shots train the immune system and how protective they might be against COVID-19.

1. What is different about the updated booster shots?

The newly authorized shots are the first updates to the original COVID-19 vaccines that were introduced in late 2020. They use the same mRNA technology as the original vaccines. The key difference between the original COVID-19 shots and the new “bivalent” version is that the latter consists of a mixture of mRNA that encodes the spike proteins of both the original SARS-CoV-2 virus and the more recent omicron subvariants, BA.4 and BA.5.

As of late August 2022, the BA.4 and BA.5 omicron subvariants are dominant worldwide. In the U.S., currently 89% of COVID-19 infections are caused by BA.5 and 11% are caused by BA.4.

The inability of the original vaccine strains to prevent reinfection and to trigger long-term protective immunity prompted the need for the reformulated vaccines.