Study: COVID-19 antibodies last longer, stay higher in those vaccinated after earlier infection

People who got two doses of a COVID-19 vaccine following an earlier infection have higher antibody levels that last longer, a new Johns Hopkins Medicine study suggests.

In a news release, Johns Hopkins said the antibody levels stayed more “durable” in those who got both jabs of the vaccine after a coronavirus infection when compared to those who only got the vaccine.

The study looked at nearly 2,000 health care workers.

“This finding adds to our understanding of how immunity against SARS-CoV-2 (the COVID-19 virus) works, and builds upon an earlier study by our team that showed the mRNA vaccines yielded a robust antibody response, even if a person did not develop significant symptoms following vaccination or did not have a prior SARS-CoV-2 infection,” study senior author Dr. Aaron Milstone, professor of pediatrics at the Johns Hopkins University School of Medicine, said in the release.

Researchers followed 1,960 Johns Hopkins Medicine health care workers who had received both doses of either the Pfizer or Moderna vaccines — both of which are messenger RNA (mRNA) vaccines.

Of those studied, 73 had a positive COVID-19 PCR test before their first vaccine dose.

“We found that health care workers with prior SARS-CoV-2 infection followed by two doses of mRNA vaccine — therefore, three independent exposures to the S1 spike protein — developed higher antibody levels than those with vaccination alone,” said study lead author Dr. Diana Zhong, an infectious diseases fellow at the Johns Hopkins University School of Medicine. “The relative differences were 14% higher at 1 month following the second vaccine dose, 19% at three months and 56% at six months.”

Zhong also said participants with confirmed infection more than 90 days before their first vaccine “had adjusted antibody levels 9% (one month following the second vaccine dose) and 13% (three months following the second vaccine dose) higher than those who were exposed to the virus less than or equal to the 90-day mark.”

“This suggests that a longer interval between infection and first vaccine dose may enhance the antibody response,” said Milstone, though he maintained further investigation was needed to determine if increased post-vaccination durability is attributable to the number of exposures to the virus, the interval between exposures, or the interplay between natural or vaccine-derived immunity.

The research letter for the study is available on the Journal of the American Medical Association website.

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Will Vitka

William Vitka is a Digital Writer/Editor for He's been in the news industry for over a decade. Before joining WTOP, he worked for CBS News, Stuff Magazine, The New York Post and wrote a variety of books—about a dozen of them, with more to come.

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