Antibody Levels of COVID-19 After Vaccination Rise Over Time for Those Infected


The difference between individuals who were vaccinated and had the infection were higher at different intervals than for those who were unvaccinated.

Antibody levels against SARS CoV-2 remain higher over an extended period for those who were infected with COVID-19 and vaccinated than those who just received a 2-dose mRNA vaccine, results of a new study by Johns Hopkins Medicine show.

“This finding adds to our understanding of how immunity against SARS-CoV-2 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,” Aaron Milstone, MD, MHS, professor of pediatrics at the Johns Hopkins University School of Medicine and pediatric epidemiologist at Johns Hopkins Children’s Center, said in a statement.

Investigators followed 1960 health care workers from Johns Hopkins Medicine who received both doses of either the Moderna or Pfizer vaccination, including 73 individuals who tested positive for COVID-19 before their first dose.

The 73 individuals were divided into 2 groups: the members of the first group were infected at 90 days or closer to the first vaccine dose, and the other group’s members were exposed to the virus more than 90 days before the shot.

Antibody levels were compared at 1, 3, and 6 months after the second vaccine dose between both groups.

Those who were vaccinated and had the infection had antibody levels that were 14% higher at 1 month following the second vaccine dose, 19% higher at

3 months, and 56% higher at 6 months than those who were just vaccinated, Diana Zhong, MD, an infectious diseases fellow at the Johns Hopkins University School of Medicine, said in the statement.

Individuals who were infected 90 days before initial vaccination had adjusted antibody levels 9% higher at 1 month and 13% higher at 3 months than those infected less than or equal to the 90-day mark, she said.

Investigators adjusted the study for age, gender, and vaccine type.

The findings were posted in the Journal of the American Medical Association.


In Covid-19 vaccinated people, those with prior infection likely to have more antibodies. EurekAlert. News release. November 1, 2021. Accessed November 2, 2021.

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