SARS-CoV-2 adaptive immunity in nursing home residents up to eight months after two doses of the Comirnaty® COVID-19 vaccine

Abstract

There is scant information as to how SARS-CoV-2 antibody and T-cell immune responses elicited by mRNA COVID-19 vaccines evolve in the general population, and in particular in elderly nursing home residents, who are at increased risk of developing severe clinical forms of COVID-19. We read with interest the work by Tré-Hardy and colleagues who reported a significant antibody decrease at around 6 months after full vaccination in healthcare workers, that was more marked in SARS-CoV-2 naïve vaccinees [1]. The authors suggested that in a supply-limited environment, booster dose schemes may be spared for SARS-CoV-2-experienced individuals. The data presented herein extend this observation to elderly nursing home residents. The current prospective cohort study included 680 (478 female; median age, 87 years; range 65–100) of a cohort of 881 nursing home residents initially recruited from a representative sample of Valencian Community nursing homes (n = 13) for assessment of SARS-CoV-2 immune responses at a median of 3 months (3 M) following full-dose Comirnaty® COVID-19 vaccination [2] who were re-examined at a median of 219 days (range, 139–246) after vaccination (7 M). Out of the 680 participants, 238 had been infected by SARS-CoV-2 prior to receiving the first vaccine dose, as recorded in the electronic Valencia Health System Integrated Databases. Two residents contracted the infection (Delta variant, as documented by whole-genome sequencing) between sampling times (3 M and 7 M). The remaining 440 participants were presumably naïve for SARS-CoV-2 at the time of sampling (7 M).