Investigation of Possible Factors Influencing the Neutralizing Anti-SARS-CoV-2 Antibody Titer after Six Months from the Second Vaccination Dose in a Sample of Italian Nursing Home Personnel

Abstract

The titer of the anti-SARS-CoV-2 antibodies produced after vaccination shows a relevant decay over time, as demonstrated in several studies. However, less is known on the possible factors affecting the entity of this decay. The aim of this study is to analyze a group of individual factors which are possibly associated with anti-SARS-CoV-2 antibody titer decay six months after the second vaccine dose. We report here the results of a follow-up serological analysis and a questionnaire-based evaluation of a sample of workers from an Italian nursing home, vaccinated with two doses of BNT162b2 vaccine in early 2021. The baseline data were collected one month after the vaccine, while in the present analysis we report the data collected six months later. Our data show a relevant decay of the neutralizing antibody titer, even if for all the workers a largely positive response was detected. Moreover, our results demonstrate a possible association between younger age and the absence of previous COVID-19 infection, and a higher decay rate of the anti-SARS-CoV-2 antibodies titer.

Antibody responses to BNT162b2 SARS‐CoV‐2 mRNA vaccine among healthcare workers and residents of long‐term care facilities: A cohort study in Northern Italy

“…This cohort study conducted among HCWs and residents of 13 LTCFs in Northern Italy found IgG titers 2 weeks after a full vaccination cycle were significantly upregulated compared with before vaccination among all participants. Our results add to an emerging literature supporting the real‐life effectiveness of mRNA vaccines in inducing detectable antibody responses in this setting 2,13,16–19 …”

“…Our results add to an emerging literature supporting the real‐life effectiveness of mRNA vaccines in inducing detectable antibody responses in this setting. 2 , 13 , 16 , 17 , 18 , 19 …”

“…Finally, it must also be noted that, as previously discussed, seropositivity may not correlate with protection against reinfection; it is known that the antibodies are only a part of the immune machine, as the role of memory T cells in killing virus-infected cells is equally fundamental. 8,13 It remains to be determined whether infection risk will be…”

“… 4 , 8 , 9 , 10 This issue is important as older adults are the population at higher risk of developing severe COVID‐19. 11 , 12 , 13 , 14 …”

Evolution of antibody titers after two doses of mRNA Pfizer-BioNTech vaccine and effect of the third dose in nursing home residents

“…Facility staff were also included in the priority group for vaccination [13][14][15][16]. Nursing home staff can be a source of transmission for residents and may also be exposed to contagion when attending to residents´physical care needs.…”