Does the bivalent COVID-19 booster vaccine help protect against getting sick from COVID-19?


Short answer: yes! The bivalent booster vaccine does give additional protection against symptomatic COVID-19 infections for people who had previously received the OG COVID-19 mRNA vaccines.

In September 2022, the US Advisory Committee on immunization Practices (ACIP) recommended that all persons aged 12 and up who had already gotten their primary series of COVID-19 vaccines get the new and improved bivalent COVID-19 booster vaccine. This vaccine contains components of both the original strain of SARS-CoV-2 and the Omicron BA.4/BA.5 strains. The recommendation was expanded in October to include kids aged 5 and up.

The recommendations were based on immunogenicity data (looking at antibodies after getting a vaccine). While this is helpful data to know, it does not always translate into meaningful clinical outcomes. The next step is to measure if the vaccine prevented real world stuff that people care about, like “was I less likely to get sick if I get this vaccine?”

The CDC has just published a new study that answers that very question! They looked at the effectiveness of the bivalent booster to prevent symptomatic COVID-19 infections compared to the monovalent (only had the original strain) vaccines. Between September 14 to November 11, 2022, they tested COVID-19 for adults in retail pharmacies who came in with symptoms that could be COVID-19 and did not have any immunocompromising conditions. They wanted to know what the rates of COVID-19 looked like for people who had prior mRNA vaccine doses, how long ago, and if they got the booster shot.
They found that the relative vaccine effectiveness (rVE) of the bivalent booster compared with at least 2 doses of the monovalent vaccine 2-3 months after the last monovalent dose was 30% for ages 18-49 years, 31% for ages 50-64 and 28% for 65 years and up. This means that the bivalent booster adds protection compared to just getting the monovalent vaccines. Probably because of waning immunity, there was an even bigger boost in rVE for folks who had gotten their last vaccine 8 months or more before the bivalent vaccine dose.

This study gives us some important information and some lingering questions:

👉 Bivalent boosters added protection when Omicron BA.4/BA.5 strains were the predominant circulating strains. This is important: we know that the original monovalent vaccine efficacy went down when these strains took over.

🙌 The bivalent boosters were helpful at restoring protection after immune waning. We know this because the relative vaccine effectiveness increased with longer time since the last monovalent dose.

🤔 This does not tell us if prior infections, exposure risk, or behaviors (like wearing a mask or avoiding indoor crowds) impact the vaccine effectiveness.

❓ We don’t know how well the vaccine protects people who have weakened immune systems. Those people were not included in this study.

❗️ This is the first patient-oriented outcome for the bivalent vaccine. It looks at something that matters to people (getting a symptomatic infection) compared to a lab value (amount of antibodies).

Only about 12% of eligible people in the US have received the bivalent COVID-19 booster. This study adds more support to getting boosted! As COVID-19, flu, and RSV are on the rise and the tripledemic is kicking our healthcare system’s collective butts, getting boosted is more important than ever.

Stay safe. Stay well. Get boosted!
Those Nerdy Girls


CDC MMWR Effectives of Bivalent mRNA Vaccines in Preventing Symptomatic SARS-CoV-2 Infection

CDC COVID Data Tracker

WHO Primer on Vaccine Efficacy and Effectiveness

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