A Michigan Medicine study found that most patients with mild COVID-19 infections produce antibodies that persist and protect them from reinfection for up to six months.
Researchers analyzed data from 130 people with PCR-confirmed COVID-19 illness between three and six months after initial infection. Three patients were hospitalized while the rest were treated as outpatients and experienced mild infection, with symptoms including headaches, chills and loss of taste or smell.
The results, published in Microbiology Spectrum, found that approximately 90% of participants produced spike and nucleocapsid antibody responses, and all but one had persistent antibody levels at follow up.
The prospective study’s participants were either Michigan Medicine healthcare workers or patients with a high risk of exposure to COVID-19. Most subjects took part in the same research team’s previous study, which found that COVID-19 antibody tests are effective at predicting prior infection.
During the observation period, none of the subjects who produced antibodies were re-infected, compared to 15 antibody-negative patients. Schuler’s team also found that the antibodies’ ability to neutralize COVID-19 did not differ significantly from the first visit, which occurred three months after infection to the second visit at the six-month mark.
The team of researchers is now analyzing samples from this group taken up to a year after infection to further evaluate antibody responses.
The research was conducted between March 2020 and February 2021, months before the highly transmissible Delta variant became the dominant strain of COVID-19 in the United States.