Had COVID-19? One vaccine dose enough, study finds

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Two mRNA vaccines against COVID-19 have proven safe and effective in clinical trials, as well as in the millions of people who have been vaccinated so far.

But how prior SARS-CoV-2 infection affects vaccine response, and how long that response lasts, are still uncertain.

In a new study from…, researchers found that people who had COVID-19 need only one vaccine dose, and that boosters could be necessary for everyone in the future.

In clinical trials, the Pfizer-BioNTech and Moderna COVID-19 vaccines were about 95% effective in protecting against symptomatic infections.

Both mRNA vaccines trigger the immune system to produce antibodies against the SARS-CoV-2 spike protein receptor-binding domain (RBD), and two doses are necessary to provide immunity in people who haven’t previously had COVID-19.

In the study, the team wanted to compare antibody levels, quality and persistence after one and two doses of mRNA vaccine in people with or without prior SARS-CoV-2 infection.

They measured antibodies in people who received the Pfizer-BioNTech or Moderna vaccine, and in unvaccinated people soon after mild or severe COVID-19 cases.

In the 28 participants without prior infection, one dose of either vaccine triggered antibody levels similar to those seen after mild COVID-19 infections, whereas two doses were required to obtain anti-RBD antibodies approaching those observed after severe cases.

In contrast, in 36 participants who had COVID-19 prior to vaccination, the first dose produced a vigorous antibody response similar to severe natural infection, but the second dose provided no additional increase in antibody levels.

The quality of antibodies, indicated by their ability to neutralize the SARS-CoV-2 spike protein and their potency, followed similar patterns.

After the second vaccine dose, antibody levels waned in both groups comparably to natural infection, resulting in an average loss of 90% within 85 days.

Although more research on T cell responses to the vaccines is needed, this result suggests that booster vaccinations will likely be required for everyone, the researchers say.

If you care about COVID-19 vaccines, please read studies about this new vaccine can block COVID-19 and variants, plus other coronaviruses and findings of mounting evidence suggests COVID vaccines do reduce transmission.

For more information about COVID vaccines and your health, please see recent studies about COVID vaccines: some fully vaccinated people will still get infected – here’s why and results showing that many Americans take immune-weakening drugs that may lower COVID vaccine response.

The study is published in ACS Nano. One author of the study is Otto Yang.

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