People who reported experiencing side effects to the Pfizer/BioNTech and Moderna Covid-19 vaccines such as fever, chills or muscle pain tended to have a greater antibody response following vaccination, according to new research.
Having such symptoms after vaccination is associated with greater antibody responses compared with having only pain or rash at the injection site or no symptoms at all, suggests the paper published Friday in the journal JAMA Network Open.
"In conclusion, these findings support reframing postvaccination symptoms as signals of vaccine effectiveness and reinforce guidelines for vaccine boosters in older adults," the researchers -- from Columbia University in New York, University of Vermont and Boston University -- wrote in their paper.
But even though some people may have small, localized side effects or no symptoms at all, the vaccine still elicits robust immune responses in them too. Nearly all study participants exhibited a positive antibody response after completing a two-dose Pfizer/BioNTech or Moderna vaccine series.
"I don't want a patient to tell me that, 'Golly, I didn't get any reaction, my arm wasn't sore, I didn't have fever. The vaccine didn't work.' I don't want that conclusion to be out there," said Dr. William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center and medical director of the National Foundation for Infectious Diseases, who was not involved in the new study.
"This is more to reassure people who have had a reaction that that's their immune system responding, actually in a rather good way, to the vaccine, even though it has caused them some discomfort," Schaffner said.
The researchers analyzed data on 928 adults who self-reported what symptoms they experienced after receiving Pfizer/BioNTech or Moderna Covid-19 vaccinations, as well as submitted a dried blood spot to test for antibodies. Most of the participants were White adults, with a mean age of 65.
The researchers found that after either vaccine dose, 446 or 48 per cent of participants reported systemic symptoms while 12 per cent reported only local symptoms and 40% reported no symptoms at all.
Meanwhile, antibody reactivity was observed in 444 or 99 per cent of participants with systemic symptoms, 99 per cent of those with only local symptoms and 98% of those with no symptoms.
"A lot of people have speculated over the years whether people who had more of a reaction to the vaccine might actually have that represent a more vigorous immune response," Schaffner said. "And these data would appear to support that."
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