A paper published by Krutikov and others in The Lancet June 2021 aimed to investigate the association between SARS-CoV-2 antibody status and subsequent infections within a population in a long term care facility.
They undertook a prospective cohort study of SARS-CoV-2 infection in staff aged under 65 years and residents aged over 65 years at 100 long term care facilities in England between October 1st 2020 and February 1st 2021.
Blood samples were collected between June and November 2020 at baseline and two and four months thereafter and tested for IgG antibodies to SARS-CoV-2 nucleocapsid and spike proteins.
PCR testing for SARS-CoV-2 was done weekly in staff and monthly in residents.
They found that IgG antibodies to nucleocapsid were detected in 33% of the 682 residents and 29% of the 1429 staff members.
93, 20% of the 456 residents were antibody negative at baseline had a PCR positive test infection rate 0.054 per month risk compared with 4, 2% of the 226 residents who were antibody positive at baseline.
11,1 that is 11% of the 1021 staff members who were antibody negative at baseline had PCR positive tests with a rate of 0.042 per month at risk compared with 10, 2% of the 408 staff members were antibody positive staff at baseline 0.009 nine per month at risk.
The risk of PCR positive infection was higher for residents who were antibody negative at baseline than residents who were antibody positive at baseline.
The risk of a PCR positive infection was also higher for staff who were antibody negative at baseline compared with staff who were antibody positive at baseline.
Antibody titres to spike nucleocapsid proteins were comparable in the PCR positive and PCR negative to cases.
They concluded that the presence of IgG antibodies to nucleocapsid protein was associated with a substantially reduced risk of reinfection in staff and residents for up to 10 months after primary infection.
They also found that any observed re-infections were not clinically severe.
They concluded that understanding the correlates of immunity that protect against future infection will be fundamental to policy decisions regarding long term care facilities including revaccination schedules and the ongoing need for non-pharmaceutical interventions to prevent SARS-CoV-2 transmission.
The London General Practice is proud to be on the Government website for all aspects of COVID-19 testing. As the leading London doctors’ clinic, it provides a full healthcare service for all aspects of COVID disease including COVID testing, COVID assist for those suffering with COVID and a multidisciplinary team to help those with long COVID or post-acute COVID.
Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed