A small study led by the UK Coronavirus Immunology Consortium (UK CIC) found that a T-cell response against SARS-CoV-2 was present 6 months after infection, in a group of 100 healthcare workers.
Blood and serum samples were collected from more than 2,000 medical staff including 23 males and 77 females who tested seropositive for SARS-CoV-2 in March and April 2020. These individuals reported mild to moderate symptoms or were asymptomatic. Antibody levels were measured in serum samples that were collected monthly. The T-cell response was measured in blood samples taken after 6 months.
Immune responses were detected in all 100 participants 6 months after infection although the T-cell response was 50% higher in symptomatic individuals. The study also found that the magnitude of the T-cell response was strongly correlated with the magnitude of the peak antibody response.
Why it matters: Previous studies have suggested that levels of antibodies against the SARS-CoV-2 virus decline after a few months. This is the first study to demonstrate that cellular (T-cell) immunity persists several months after infection in individuals with mild/moderate or asymptomatic COVID-19. Researchers have yet to fully understand how previous SARS-CoV-2 infections can prevent reinfection which will require large-scale population studies.