COVID-19 booster shots prompt stronger, longer protection than original shots

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In a new study from Northwestern University, researchers found COVID-19 booster shots trigger much stronger and longer protection than full vaccination with two doses of the Pfizer or Moderna vaccines.

They also found that the response to a booster is even greater in fully vaccinated people who have had infections.

In this study, the researchers analyzed blood samples from 33 healthy, fully vaccinated young adults in the Chicago area. Their median age was 43, meaning half were older, half younger.

They found nine months after the people had two doses of the Pfizer or Moderna vaccines, their neutralizing antibody levels to SARS-CoV-2 had decreased about 10-fold.

After a booster shot, antibody levels rose 25-fold—five times higher than after two doses of the vaccine. Booster antibodies were 50 times higher than those from natural infections.

The researchers said booster doses trigger a high level of neutralizing antibodies against the Delta variant, which should provide much protection.

However, the response was even higher against the original version of the virus because it’s the one that vaccines target.

The team says the findings are relevant to anyone who is considering a booster shot.

The mRNA vaccines provide a high level of protection against serious cases of COVID-19 that lead to hospitalization or death.

But immunity wanes over time—particularly levels of antibodies that help prevent infection—and we are seeing higher rates of breakthrough infections as a result, particularly in combination with the rise of the more infectious Delta variant.

Since the pandemic began, the researchers have been evaluating antibody responses from natural infection and after each dose of COVID vaccines, and have published a number of studies with their findings.

They will continue to evaluate antibody levels over time and monitor breakthrough infections to assess waning immunity.

If you care about COVID booster, please read studies about do I need a COVID-19 booster shot? 6 questions answered on how to stay protected and findings of do I need a booster shot if I got the Johnson & Johnson vaccine? A virologist answers 5 questions.

For more information about COVID booster and your health, please see recent studies about what you should know about COVID-19 booster shots and third vaccine doses and results showing how long does immunity last after COVID vaccination? Do we need booster shots? 2 immunology experts explain.

The study is published on medRxiv. One author of the study is Alexis Demonbreun.

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