Previous SARS-CoV-2 Infection, Age, and Frailty Are Associated With 6-Month Vaccine-Induced Anti-Spike Antibody Titer in Nursing Home Residents.

OBJECTIVES: Older nursing home residents make up the population at greatest risk of morbidity and mortality from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. No studies have examined the determinants of long-term antibody responses post vaccination in this group. DESIGN: Longitudinal cohort study. SETTING AND PARTICIPANTS: Residents from 5 nursing homes assessed before vaccination, and 5 weeks and 6 months post vaccination, with the BNT162b2 messenger RNA SARS-CoV-2 vaccine. METHODS: Comprehensive clinical assessment was performed, including assessment for comorbidity, frailty, and SARS-CoV-2 infection history. Serum nucleocapsid and anti-spike receptor binding domain (RBD) antibodies were analyzed at all timepoints. An in vitro angiotensin-converting enzyme (ACE2) receptor-spike RBD neutralization assay assessed serum neutralization capacity. RESULTS: Of 86 participants (81.1 ± 10.8 years; 65% female), just under half (45.4%; 39 of 86) had evidence of previous SARS-CoV-2 infection. All participants demonstrated a significant antibody response to vaccination at 5 weeks and a significant decline in this response by 6 months. SARS-CoV-2 infection history was the strongest predictor of antibody titer (log-transformed) at both 5 weeks [ß: 3.00; 95% confidence interval (CI): 2.32-3.70; P < .001] and 6 months (ß: 3.59; 95% CI: 2.89-4.28; P < .001). Independent of SARS-CoV-2 infection history, both age in years (ß: -0.05; 95% CI: -0.08 to -0.02; P < .001) and frailty (ß: -0.22; 95% CI: -0.33 to -0.11; P < .001) were associated with a significantly lower antibody titer at 6 months. Anti-spike antibody titers at both 5 weeks and 6 months significantly correlated with in vitro neutralization capacity. CONCLUSIONS AND IMPLICATIONS: In older nursing home residents, SARS-CoV-2 infection history was the strongest predictor of anti-spike antibody titers at 6 months, whereas age and frailty were independently associated with lower titers at 6 months. Antibody titers significantly correlated with in vitro neutralization capacity. Although older SARS-CoV-2 naïve nursing home residents may be particularly vulnerable to breakthrough SARS-CoV-2 infection, the relationship between antibody titers, SARS-CoV-2 infection, and clinical outcomes remains to be fully elucidated in this vulnerable population.

High anti-SARS-CoV-2 antibody seroprevalence in healthcare workers in an Irish university teaching hospital.

INTRODUCTION: Healthcare workers are at very high risk for SARS-CoV-2 exposure and infection. This study evaluated anti-SARS-CoV-2 seroprevalence in healthcare workers in a tertiary care hospital and then correlated seroprevalence with confirmed or suspected SARS-CoV-2 infection in this population since the onset of the COVID-19 pandemic. METHOD: The study was approved by our institution's Joint Research Ethics Committee in June 2020. All volunteers were provided with a consent form, an information leaflet and a questionnaire on the day before phlebotomy. Serum samples were collected from 1176 participants over a 3-month period and analysed using the Elecsys Anti-SARS-CoV-2 assay (Roche Diagnostics GmbH, Mannheim, Germany) which detects total antibodies against the nucleocapsid protein of SARs-COV-2. RESULTS: Overall anti-SARS-CoV-2 seroprevalence among participating healthcare workers was 17.9%. The rate of confirmed infection by real-time polymerase chain reaction molecular testing prior to participation was 12.2%. Of 211 participants who had a reactive antibody test result, 37% did not have COVID-19 infection confirmed at any point prior to participation in this study, either having had a swab which did not detect SARS-CoV-2 RNA or having never been tested. Seropositivity was the highest (30%) in the youngest quintile of age (20-29 years old). Staff with more patient contact had a higher seroprevalence of 19.5% compared to 13.4% in staff with less patient contact. CONCLUSION: This study demonstrates that a substantial proportion of SARS-CoV-2 infections in healthcare workers may be asymptomatic or subclinical and thus potentially represent a significant transmission risk to colleagues and patients.