(HealthDay News) — Natural immunity protects against reinfection with the alpha and beta variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), according to a study published online Dec. 15 in the New England Journal of Medicine.
Hiam Chemaitelly, Ph.D., from Weill Cornell Medicine-Qatar in Doha, and colleagues estimated the efficacy of immunity induced by natural infection against reinfection by comparing the incidence of SARS-CoV-2 reinfection in a cohort of persons who had previous confirmed infection before Jan. 1, 2021, with incidence in a cohort of antibody-negative individuals with no evidence of previous infection using data from national databases in Qatar. Participants were followed from March 8 to April 21, 2021.
The researchers found that at 42 days of follow-up, the cumulative incidence was 0.27 and 3.44% in the previous-infection cohort and antibody-negative cohort, respectively, for the beta variant, and was 0.03 and 1.35%, respectively, for the alpha variant. The incidence rates of infection with the beta variant were estimated at 4.34 and 56.25 cases per 10,000 person-weeks in the previous infection and antibody-negative cohorts, respectively; for the alpha variant, the corresponding incidence rates were 0.53 and 22.44 cases per 10,000 person-weeks. The efficacy of natural infection against reinfection was estimated at 92.3 and 97.6% for the beta and alpha variants, respectively.
“These findings give some insights into the hypothesis that natural immunity may provide protection against known variants of concern,” the authors write.
