Studies have found immune responses in patients with mild COVID-19 last months, and probably longer. Recent findings indicated that antibodies decline in slightly ill patients, and shortly after recovery, immunity wanes. Yet a report on 349 COVID-19 patients from China last month, which has not yet undergone peer review, reported similar trends of immune response at six months, regardless of the extent of the symptoms.
And in a study published Saturday ahead of peer review, U.S. researchers conducted blood tests after mild COVID-19 in 15 patients, looking for three signs of lasting immune responses: antibodies, so-called memory B cells, and memory T cells. Three months after recovery, patients still had “all three of these layers of defense,” reducing their risk of reinfection, the University of Washington School of Medicine study co-author Lauren Rodda told Reuters. When they become reinfected, they ‘re less likely to become seriously sick or become infectious, Rodda said.
Test results were unchanged at three months from tests at one month, and her team assumes this is a permanent answer. Since the results last three months indicate immune responses, if not longer, Rodda said, they are helping the U.S. Disease Control and Prevention Centers warn that patients do not need to be retested for COVID-19 within the first three months of infection.