(HealthDay News) — The presence of immunoglobulin G (IgG) antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein is associated with a reduced risk for reinfection at long-term care facilities (LTCFs), according to a study published in the June issue of The Lancet Healthy Longevity.
Maria Krutikov, M.B.Ch.B., from the University College London Institute of Health Informatics, and colleagues conducted a prospective cohort study of SARS-CoV-2 infection in 682 residents from 86 LTCFs and 1,429 staff members from 97 LTCFs from Oct. 1, 2020, to Feb. 1, 2021. Blood samples were obtained between June and November 2020 and were tested for IgG antibodies to SARS-CoV-2 nucleocapsid and spike proteins.
The researchers found that 33 and 29% of the residents and staff members, respectively, had IgG antibodies to nucleocapsid at baseline. The infection rate was 0.054 per month at risk for residents who were antibody-negative at baseline compared with 0.007 for those who were antibody-positive at baseline. Among staff members, the corresponding infection rates were 0.042 versus 0.009 per month at risk. The risk for polymerase chain reaction-positive infection was lower for residents and staff who were antibody-positive versus those who were antibody-negative at baseline (adjusted hazard ratios, 0.15 and 0.39, respectively). Eleven of the 12 reinfected participants with available data on symptoms were asymptomatic.
“Understanding the correlates of immunity that protect against future infection will be fundamental to policy decisions regarding LTCFs, including revaccination schedules and the ongoing need for nonpharmaceutical interventions to prevent SARS-CoV-2 transmission,” the authors write.