Immunogenicity after 6 months of BNT162b2 vaccination in frail or disabled nursing home residents: The COVID‐A Study.

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. [ABSTRACT FROM AUTHOR]