A T-cell response, or cellular immunity, was present in 100 people six months after their initial COVID-19 infection, according to a study published in the preprint server BioRxiv.
Researchers from the University of Birmingham in England collected serum and blood samples from more than 2,000 clinical and non-clinical healthcare workers, including 100 who tested positive for COVID-19 in March and April. To measure antibody levels, serum samples were collected monthly and blood samples were collected after six months to analyze T-cell response. Immune responses were detected in all 100 participants six months after infection.
People who were symptomatic had about a 50 percent higher response size than people who were asymptomatic — a notable find, according to researchers. All positive cases in the study were mild, moderate or asymptomatic infections. None required hospitalization.
"To our knowledge, our study is the first in the world to show robust cellular immunity remains at six months after infection in individuals who experienced either mild/moderate or asymptomatic COVID-19," said Paul Moss, PhD, a hematology professor at the University of Birmingham and lead of the U.K.'s Coronavirus Immunology Consortium. "We now need more research to find out if symptomatic individuals are better protected against reinfection in the future."
The study has not yet been peer-reviewed.