To date, there is limited evidence of reinfection in humans with previously documented COVID-19… Most studies of immune protection against SARS-CoV-2 in humans have focused on the induction of neutralizing antibodies. But antibody responses tend to wane and are not detectable in all patients, especially those with less severe forms of COVID-19. “It will therefore be critical in light of the ongoing pandemic to determine if people with milder forms of COVID-19 develop robust immunity against SARS-CoV-2,” [the authors] commented.
To address this gap in knowledge, [researcher Marcus] Buggert and his collaborators assessed SARS-CoV-2-specific T cell and antibody responses in more than 200 individuals from Sweden across the full spectrum of exposure, infection, and disease. “ … we used a systematic approach to map cellular and humoral immune responses against SARS-CoV-2 in patients with acute moderate or severe COVID-19, individuals in the convalescent phase after mild or severe COVID-19, exposed family members, and healthy individuals who donated blood before (2019) or during the pandemic (2020),” they wrote.
“Our findings suggest that the reliance on antibody responses may underestimate the extent of population-level immunity against SARS-CoV-2,” Buggert says. “The obvious next step is to determine whether robust memory T cell responses in the absence of detectable antibodies can protect against COVID-19 in the long term.”