Prior infection identified as a potential predictor of adverse reactions.
People who recovered from COVID-19 and received a COVID-19 shot were more likely to suffer adverse reactions, researchers in Europe are reporting.
Participants in the study were more likely to experience an adverse reaction after vaccination regardless of the type of shot, with one exception, the researchers found.
Across all vaccine brands, people with prior COVID-19 were 2.6 times as likely after dose one to suffer an adverse reaction, according to the new study. Such people are commonly known as having a type of protection known as natural immunity after recovery.
People with previous COVID-19 were also 1.25 times as likely after dose 2 to experience an adverse reaction.
The findings held true across all vaccine types following dose one.
Of the female participants who received the Pfizer-BioNTech vaccine, for instance, 82 percent who had COVID-19 previously experienced an adverse reaction after their first dose, compared to 59 percent of females who did not have prior COVID-19.
The only exception to the trend was among males who received a second AstraZeneca dose. The percentage of males who suffered an adverse reaction was higher, 33 percent to 24 percent, among those without a COVID-19 history.
“Participants who had a prior SARS-CoV-2 infection (confirmed with a positive test) experienced at least one adverse reaction more often after the 1st dose compared to participants who did not have prior COVID-19. This pattern was observed in both men and women and across vaccine brands,” Florence van Hunsel, an epidemiologist with the Netherlands Pharmacovigilance Centre Lareb, and her co-authors wrote.
There were only slightly higher odds of the naturally immune suffering an adverse reaction following receipt of a Pfizer or Moderna booster, the researchers also found.
The researchers performed what’s known as a cohort event monitoring study, following 29,387 participants as they received at least one dose of a COVID-19 vaccine. The participants live in a European country such as Belgium, France, or Slovakia.
Overall, three-quarters of the participants reported at least one adverse reaction, although some were minor such as injection site pain.
