Background The impact of coronavirus disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) on residents of long-term care facilities (LTCFs) has been dramatic on global scale as older age and comorbidities pose an increased risk of severe disease and death. Methods Aim of this study was to evaluate SARS-CoV-2 Spike-specific IgG (S-IgG) antibody titers in 478 residents and 649 health care workers of a large Italian long-term care facility two months after complete vaccination with BNT162b2. Associations among resident-related factors and predictors of humoral response were investigated. Results By stratifying levels of humoral responses, we found that 62.1%, 21.6%, 12.1% and 4.2% of residents had high (>1,000 BAU/ml), medium (101-1,000), low (1-100) and null (<1 BAU/mL) S-IgG titers, respectively. Residents with documented previous COVID-19 and those with SARS-CoV-2 nucleocapsid-specific IgG (N-IgG) positive serology showed higher level of serological response, while significant associations were observed for cancer with suboptimal response (p = 0.005) and the administration of corticosteroid for suboptimal response (p = 0.028) and a null one (p = 0.039). According to multivariate logistic regression, predictors of an increased risk of null response were advanced age (Odd ratio, OR: 2.630; Confidence interval, CI: 1.13-6.14; p = 0.025), corticosteroid therapy (OR: 4.964; CI: 1.06-23.52; p = 0.042) and diabetes mellitus (OR:3.415; CI:1.08-10.8; p = 0.037). In contrast, previous diagnosis of COVID-19 was strongly associated with a reduced risk of null response to vaccination (OR:0.126; CI:0.02-0.23; p < 0.001). Conclusions SARS-CoV-2 specific antibodies in elderly individuals should be consider when deciding the need of a third dose of vaccine for prevention of reinfections in LTCFs despite the maintenance of barrier measures.

Residents of long-term care facilities (LTCFs) have been dramatically hit by the COVID-19 pandemic on a global scale as older age and comorbidities pose an increased risk of severe disease and death. The aim of the study was to assess the quantity and durability of specific antibody responses to SARS-CoV-2 after the first cycle (two doses) of BNT162b2 vaccine. To achieve this, SARS-CoV-2 Spike-specific IgG (S-IgG) titers was evaluated in 432 residents of the largest Italian LTCF at months 2 and 6 after vaccination. By stratifying levels of humoral responses as high, medium, low and null, we did not find any difference when comparing the two time points; however, the median levels of antibodies halved overtime. As positive nucleocapsid serology was associated with a reduced risk of a suboptimal response at both time points, we conducted separate analyses accordingly. In subjects with positive serology, the median level of anti-S IgG slightly increased at the second time point, while a significant reduction was observed in patients without previous exposure to the virus. At month 6, diabetes alone was associated with an increased risk of impaired response. Our data provide additional insights into the longitudinal dynamics of the immune response to BNT162b2 vaccination in the elderly, highlighting the need for SARS-CoV-2 antibody monitoring following third-dose administration.

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Background: The impact of coronavirus disease 2019 caused by Severe Acute Respiratory Syndrome Coronavirus 2 on hosts of Long Term Care Facilities (LTCFs) has been dramatic at global scale as aging and comorbitities pose individuals at increased risk of severe disease and death. Methods: Aim of this study was to evaluate SARS-CoV-2 S-IgG antibodies titers in 478 residents and 649 health care workers of the largest Italian nurse facility two months after the complete vaccination with BNT162B2. Associations among host-related factors and predictors of humoral response were investigated. Results: By stratifying levels of humoral responses, we found that 62.1%, 21.6%, 12.1% and 4.2% of hosts has high (>1,000 BAU/ml), medium (101-1,000), low (1-100) and null (<1 BAU/mL) S-IgG titers, respectively. Hosts with previous COVID-19 and those with SARS-CoV-2 N-IgG positive serology showed higher level of serological response (p<0.001 and p<0.001, respectively), while the administration of corticosteroid or cancer diminished all levels of specific antibodies (p=0.019 and p=0.004). Significant associations were observed for these parameters in those with suboptimal response (p<0.001, p<0.001, p=0.028 and p=0.005) and with a null one (p=0.005, p<0.001 and p=0.039). Predictors of an increased risk of null response were advanced age, corticosteroid therapy and diabetes mellitus (p=0.025, p=0.017 and p=0.037). In contrast, previous diagnosis of COVID-19 resulted strongly associated with a reduced risk of null response to vaccination (p<0.001). Conclusions: SARS-CoV-2 specific antibodies in elderly individuals need to be measured to consider a third dose of vaccine after mass vaccination for prevention of reinfections in LTCFs despite the maintenance of barrier measures.

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