Healthcare worker study shines light on who is most at risk of a vaccine reaction

A study in nearly 1,000 healthcare workers has pinpointed factors that may boost the odds of having a reaction to a COVID-19 mRNA vaccine.

Researchers queried workers in the Johns Hopkins Health System in Baltimore and collected serum samples 14 or more days after they received the second dose of the Pfizer or Moderna mRNA COVID-19 vaccine.

Among 954 workers, 5% reported clinically significant symptoms after the first dose and 43% did so after dose 2. The odds of having significant symptoms were higher for the Moderna vaccine than the Pfizer vaccine, investigators found. In addition, prior SARS-CoV-2 exposure appeared to raise the odds of having clinically significant symptoms following dose 1, but not dose 2.

Other factors that independently raised the odds that participants would report clinically significant post-vaccine symptoms were age younger than 60 years and female sex, after results were adjusted for time after receiving dose 2.

100% have strong antibody response

No matter their symptoms, nearly 100% of participants developed antibodies to the SARS-CoV-2 spike protein in 14 or more days following dose 2. Notably, one participant who was taking immunosuppressant medication did not develop these IgG antibodies. 

Spike IgG antibody measurements were higher in the workers who received the Moderna vaccine, had a prior SARS-CoV-2 infection, and reported clinically significant reactions, reported Amanda K. Debes, Ph.D., and colleagues. “The role of higher antibody levels in preventing COVID-19 and providing lasting immunity remains unknown, however,” she noted.

“Overall, the findings suggest that regardless of vaccine reactions or prior SARS-CoV-2 infection, either spike mRNA vaccine will provide a robust spike antibody response,” the investigators concluded.

Full findings were published in JAMA Internal Medicine.