Unvaccinated healthcare workers showed similar levels of antibodies to vaccinated ones.
A recent study, conducted by investigators from the Barcelona Institute for Global Health, in collaboration with the Catalan Health Institute, has discovered that most people maintain antibodies for SARS-CoV-2 regardless of symptoms for months, potentially years, after infection.
Results from the study were published in the journal BMC Medicine.
"The results obtained until now lead us to believe that immunity to SARS-CoV-2 will last longer than we originally thought,” Anna Ruiz Comellas, co-author on the study said. “Being a new virus, it is very important to understand how it behaves and affects different people.”
For the study, the team of investigators took blood samples from 173 healthcare workers who had an infection with COVID-19. The majority of the cases were deemed mild to moderate, though some cases did require hospitalization.
They then measured the samples for level and type of SARS-CoV-2-specific antibodies.
Findings from the study showed that there was no significant decay in observable antibodies within the first 5 months. At 9 months, 92.4% remained seropositive, with 90% having IgG, 76% having IgA and 61% having IgM.
Additionally, there were 4 reinfections observed among the participants, with 2 of them being symptomatic. Another case was observed in an individual with very low antibody levels.
“Considering that antibody levels achieved by COVID-19 immunization are usually higher than those elicited following natural infection, based on this study, it could be speculated that immune memory induced by the first-generation vaccines could also be long-lasting; therefore, reducing the probability that periodic boosters might be required to sustain protective immunity, at least within the first year,” the authors wrote. “Furthermore, data indicates that naïve people should be prioritized for vaccination over those who had suffered COVID-19, since the latter maintain antibodies for at least a year.”