Incidence of SARS-CoV-2 infection according to baseline antibody status in staff and residents of 100 long-term care facilities (VIVALDI): a prospective cohort study

Abstract

Background SARS-CoV-2 infection represents a major challenge for long-term care facilities (LTCFs) and many residents and staff are seropositive following persistent outbreaks. We aimed to investigate the association between the SARS-CoV-2 antibody status at baseline and subsequent infection in this population. MethodsWe did a prospective cohort study of SARS-CoV-2 infection in staff (aged <65 years) and residents (aged >65 years) at 100 LTCFs in England between Oct 1, 2020, and Feb 1, 2021. Blood samples were collected between June and November, 2020, at baseline, and 2 and 4 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. Cox regression was used to estimate hazard ratios (HRs) of a PCR-positive test by baseline antibody status, adjusted for age and sex, and stratified by LTCF. Findings 682 residents from 86 LCTFs and 1429 staff members from 97 LTCFs met study inclusion criteria. At baseline, IgG antibodies to nucleocapsid were detected in 226 (33%) of 682 residents and 408 (29%) of 1429 staff members. 93 (20%) of 456 residents who were antibody-negative at baseline had a PCR-positive test (infection rate 0•054 per month at risk) compared with four (2%) of 226 residents who were antibody-positive at baseline (0•007 per month at risk). 111 (11%) of 1021 staff members who were antibody-negative at baseline had PCR-positive tests (0•042 per month at risk) compared with ten (2%) of 408 staff members who were antibody-positive staff at baseline (0•009 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 (adjusted HR [aHR] 0•15, 95% CI 0•05-0•44, p=0•0006), and 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 (aHR 0•39, 0•19-0•82; p=0•012). 12 of 14 reinfected participants had available data on symptoms, and 11 of these participants were symptomatic. Antibody titres to spike and nucleocapsid proteins were comparable in PCR-positive and PCR-negative cases.Interpretation The presence of IgG antibodies to nucleocapsid protein was associated with substantially reduced risk of reinfection in staff and residents for up to 10 months after primary infection.

Prevalence and duration of detectable SARS-CoV-2 nucleocapsid antibodies in staff and residents of long-term care facilities over the first year of the pandemic (VIVALDI study): prospective cohort study in England

“…It is likely that duration of follow-up was shorter because regular PCR testing, which enabled estimation of most seroconversion dates for individuals included in the sensitivity analysis (108 [93%] of 116 individuals), only became widely available from June, 2020, when whole care home testing was introduced. 21 It was not possible to ascertain how many discrete infection episodes participants experienced; however, as protection against reinfection has been described for up to 10 months in this population, 10 recurrent infections were probably relatively rare. If reinfections did occur, then the rate of seroreversion might have been slightly higher than we have reported.…”

“… 4 There is also growing evidence that previously infected individuals develop greater antibody responses to SARS-CoV-2 vaccination than people who have not been infected. 5 , 6 , 7 Robust antibody production has been shown in older LTCF residents who have survived SARS-CoV-2 infection; 8 , 9 , 10 however, there have been few large-scale sero-surveys to describe the extent of past exposure and immunity in this population.…”

Long-Term Course of Humoral and Cellular Immune Responses in Outpatients After SARS-CoV-2 Infection

“…Although our data do not allow a meaningful calculation of the half-life due to a cross-sectional design instead of longitudinal for each patient, the finding is in accordance with reports from others (14)(15)(16)(17), who calculated the half-life of neutralizing IgG antibodies with 140 to 220 days. Recently, colleagues reported that IgG antibodies to nucleocapsid protein reduced the risk of reinfection for up to 10 months after primary infection (18). Researchers from the University of Padua and Imperial College London tested more than 85% of the 3,000 residents of Vo' , Italy, in February/March 2020 for infection with SARS-CoV-2 and tested them again in May and November 2020.…”

Prevalence, Distribution and IgG Antibody Levels Associated with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Among Health-System and Community-Based Employees and Patients

“… 22 The strong immune response after a natural infection with SARS-COV-2 is also supported by the low incidence of breakthrough infections among seropositive compared to seronegative individuals across various age groups. 23 , 24 For example, in large cohort in England (n=2,111), seropositive individuals tested at least monthly were 41-85% less likely to have a positive PCR test for SARS-COV-2 when compared to seronegative individuals. 24 Thus, the immune response induced by natural infection with SARS-COV-2 should augment the COVID-19 vaccine efforts to attain herd immunity assuming that new SARS-COV-2 variants retain significant overlap in epitopes with currently circulating variants.…”