Abstract and Introduction
Abstract
Background: There is incomplete information regarding evolution of antibody titers against SARS-CoV-2 after a two-dose strategy vaccination with BNT162b2 in older adults in long-term care facilities (LTCFs) with frailty, disability, or cognitive impairment. We aimed to determine IgG antibody titer loss in older adults in LTCFs.
Methods: This is a multicenter longitudinal cohort study including 127 residents (90 females and 37 males) with a mean age of 82.7 years (range 65–99) with different frailty and disability profiles in two LTCFs in Albacete, Spain. Residents received two doses of BNT162b2 as per label, and antibody levels were determined 1 and 6 months after the second dose. Age, sex, previous history of coronavirus disease 2019 (COVID-19), comorbidity (Charlson Index), performance in activities of daily living (Barthel Index), frailty (FRAIL instrument), and cognitive status were assessed.
Results: The mean antibody titers 1 and 6 months after the second vaccine dose were 32,145 AU/ml (SD 41,206) and 6182 AU/ml (SD 13,316), respectively. Across all participants, the median antibody titer loss measured 77.6% (interquartile range [IQR] 23.8%). Notably, the decline of titers in individuals with pre-vaccination COVID-19 infection was significantly lower than in those without a history of SARS-CoV-2 infection (72.2% vs. 85.3%; p < 0.001). The median titer decrease per follow-up day was 0.47% (IQR 0.14%) and only pre-vaccination COVID-19 was associated with lower rate of antibody decline at 6 months (hazard ratio 0.17; 95% confidence interval 0.07–0.41; p < 0.001). Frailty, disability, older age, cognitive impairment, or comorbidity were not associated with the extent of antibody loss.
Conclusions: Older adults in LTCFs experience a rapid loss of antibodies over the first 6 months after the second dose of BNT162b2 vaccine. Only pre-vaccination COVID-19 is associated with a slower rate of antibody decrease. Our data support immunization with a third dose in this vulnerable, high-risk population.
Introduction
Older adults constitute the most prevalent target group of SARS-CoV-2 vaccination in most industrialized countries.[1,2] The coronavirus disease 2019 (COVID-19) pandemic has had a great impact on mortality in nursing homes and long-term care facilities (LTCFs),[3,4] and residents have been prioritized for early vaccination with mRNA COVID-19 vaccines, as they belong to the most vulnerable groups in society.[5] The use of mRNA vaccines in residents of nursing homes in Spain is 71% effective against symptomatic and asymptomatic SARS-CoV-2 infection, prevents 88% of hospitalizations, and reduces COVID-19 mortality by 97%.[6]
An antibody test to detect IgG titers provides a simple and rapid surveillance tool for potentially monitoring effectiveness of vaccines over time,[7] and this surrogate marker is considered by many particularly useful in the pandemic context to obtain early estimates of vaccine effectiveness. We have previously described that the BNT162b2 mRNA COVID-19 vaccine is safe and robustly immunogenic in older adults, independent of frailty, cognitive impairment, comorbidities, or disability profiles.[8] However, little is known about the stability of antibody levels in these high-risk individuals.
Pfizer has recognized a decrease in BNT162b2 efficacy, decreasing from 95% to 91% 6 months after the second dose of the two-dose regimen,[9] but data stratified by functional status, frailty, cognitive status, or comorbidity are not available. In a preprint, a significant increase in the risk of COVID-19 was described particularly among patients older than 60 years, who had received their last vaccine dose >146 days ago, suggesting progressive loss of vaccination induced antibody levels.[10]
The use of booster shots is an area of ongoing debate, further fueled by the emergence of more contagious strains.[11] However, most research on immunogenicity of BNT162b2 has been conducted in younger individuals with limited follow-up for only a few weeks.[12] To support decision-making specifically for older adults, and, consequently, to prevent outbreaks in LTCFs, we thus studied the development of antibody levels to BNT162b2 in older adults.
J Am Geriatr Soc. 2022;70(3):1441-1447. © 2022 Blackwell Publishing
