New York, Oct 9: According to a preprint study not yet peer-reviewed, individuals experiencing heightened side effects such as chills, tiredness, feeling unwell, and headaches following Covid-19 vaccination may be exhibiting an increased production of antibodies in their bodies.

Protection against SARS-CoV-2, the virus responsible for Covid-19, diminishes over time, and the adoption of booster shots has been limited.

Researchers from the University of California - San Francisco conducted the study, revealing that individuals experiencing these side effects after the second dose of a Covid vaccine had more antibodies against the coronavirus at one month and six months after the shot compared to those without symptoms.

The study also indicated that elevated skin temperature and heart rate correlated with higher antibody levels.

The research investigated the connection between post-vaccination symptoms, biometric changes, and neutralizing antibodies (nAB) after mRNA vaccination.

Data was collected from 363 adults who received two doses of either Pfizer-BioNTech or Moderna Covid vaccines.

“We found that certain symptoms (chills, tiredness, feeling unwell, and headache) after the second dose were associated with increases in nAB at one and six months post-vaccination, to roughly 140-160 per cent the level of individuals without each symptom,” said Ethan G. Dutcher, from the UCSF’s Department of Psychiatry and Behavioral Sciences, in the paper.

“Each additional symptom predicted a 1.1-fold nAB increase. Greater changes in skin temperature and heart rate after the second dose predicted higher nAB levels. Skin temperature had a stronger predictive relationship for six-month than one-month nAB levels,” Dutcher added.

However, it's important to note that this doesn't imply that individuals without symptoms do not mount a strong immune response. Experts emphasize that the relative increase in antibody levels among those who experienced side effects was modest.

“Lack of side effects should not be taken as a sign that the vaccine’s not working,” said Alessandro Sette, co-director of the La Jolla Institute of Immunology’s Center for Vaccine Innovation, who was not involved in the work, as quoted by the New York Times.

A previous study found that 98 per cent of people who experienced no ill effects still produced abundant amounts of antibodies, compared to 99 percent of those who had localized symptoms or worse, Sette said.

However, the researchers noted that the new findings "suggest that public health messaging could seek to reframe systemic symptoms after vaccination as desirable.