Antibody Responses After mRNA-Based COVID-19 Vaccination in Residential Older Adults: Implications for Reopening

OBJECTIVE: COVID-19 disproportionately impacts residents in long-term care facilities. Our objective was to quantify the presence and magnitude of antibody response in vaccinated, older adult residents at assisted living, personal care, and independent living communities. DESIGN: A cross-sectional quality improvement study was conducted March 15 – April 1, 2021 in the greater Pittsburgh region. SETTING AND POPULATION: Participants were older adult residents at assisted living, personal care, and independent living communities, who received mRNA-based COVID-19 vaccine. Conditions that impair immune responses were exclusionary criteria. METHODS: Sera were collected to measure IgG anti-SARS-CoV-2 antibody level with reflex to total anti-SARS-CoV-2 immunoglobulin levels, and blinded evaluation of SARS-CoV-2 pseudovirus neutralization titers. Descriptive statistics, Pearson correlation coefficients, and multiple linear regression analysis evaluated relationships between factors potentially associated with antibody levels. Spearman correlations were calculated between antibody levels and neutralization titers. RESULTS: All participants (N = 70) had received two rounds of vaccination and were found to have antibodies with wide variation in relative levels. Antibody levels trended lower in males, advanced age, current use of steroids, and longer length of time from vaccination. Pseudovirus neutralization titer levels were strongly correlated (P < .001) with Beckman Coulter antibody levels [D614 G NT50, r(s) = 0.91; B.1.1.7 (UK) NT50, r(s) = 0.91]. CONCLUSIONS AND IMPLICATIONS: Higher functioning, healthier, residential older adults mounted detectable antibody responses when vaccinated with mRNA-based COVID-19 vaccines. Data suggests some degree of immunity is present during the immediate period following vaccination. However, protective effects remain to be determined in larger studies as clinical protection is afforded by ongoing adaptive immunity, which is known to be decreased in older adults. This study provides important preliminary results on level of population risk in older adult residents at assisted living, personal care, and independent living communities to inform reopening strategies, but are not likely to be translatable for residents in nursing homes.