COVID-19 vaccine side effects associated with greater antibody response, study finds

The association between worse symptoms after vaccination and higher antibody levels against SARS-CoV-2 in subsequent months could be used to encourage reluctant patients to be vaccinated, study authors suggested.

Patients with more short-term side effects from COVID-19 vaccination have greater antibody response, a study found.

The prospective study included a cohort of U.S. patients who had not been vaccinated against or exposed to SARS-CoV-2 before receiving two shots of either of the mRNA vaccines. Outcomes included serum neutralizing antibody titers at one and six months after the second vaccine dose, as well as daily symptom surveys and objective biometric measurements after each vaccine dose. Results were published by Annals of Internal Medicine on June 11.

Overall, 363 participants (65.6% women; mean age, 52.4 years) were included in analyses of symptoms and 147 (66.0% women; mean age, 58.8 years) were included in biometric analyses. Chills, tiredness, feeling unwell, and headache after the second dose were each associated with 1.4- to 1.6-fold higher neutralizing antibody levels at one and six months. The number of symptoms and changes in skin temperature and heart rate with vaccination were all positively associated with antibody levels. Specifically, each 1-°C increase in skin temperature after the second dose was associated with 1.8-fold higher antibodies at one month and a 3.1 times increase at six months.

Limitations include that the study was conducted in 2021 among people receiving the primary vaccine series, so it's uncertain how the findings would apply to booster vaccinations, newer strains, or vaccination after COVID-19 infection, the study authors said. "It should be noted that our results do not justify inferences about any given person's level of nABs [neutralizing antibodies] or protection from SARS-CoV-2 infection. For example, although participants reporting tiredness had an average nAB level that was 1.5 times the level of those not reporting tiredness, not every person with tiredness had higher nABs than every person without tiredness," they added.

The results could potentially be used to encourage vaccination among reluctant patients, the authors said, given that concerns about side effects appear to be a barrier to SARS-CoV-2 vaccination for some.

In other COVID-19 vaccine news, an FDA advisory committee met on June 5 and recommended that vaccines for 2024 to 2025 target a SARS-CoV-2 strain within the lineage of the JN.1 variant.