Kinetics of SARS-CoV-2-Neutralising Antibodies of Residents of Long-Term Care Facilities

Abstract

Introduction Elderly residents of nursing homes (NHs) and long-term care units (LTCUs) have been shown to have a high risk of mortality and morbidity in cases of SARS-CoV-2 infection. The objective of this study was to examine the kinetics of neutralizing antibodies (NAbs) directed against the SARS-CoV-2 virus in residents of the NH and LTCU units of our University Hospital who were identified with positive serology after the first epidemic outbreak. Materials and Methods The participants included were sampled every three months for qualitative serological testing, as well as quantitative testing by neutralization tests using retroviral particles containing the S glycoprotein of SARS-CoV-2. Vaccination using the Comirnaty (Pfizer BNT162b2) vaccine begun before the last serological follow-up. Results The median NAb titer in June 2020 was 80 [40; 60] versus 40 [40; 160] three months later, showing a statistically significant decline (p < 0.007), but remained stable between the three- and six-month timepoints (p = 0.867). By nine months after vaccination, we observed a significant difference between vaccinated residents known to have positive serology before vaccination (SERO+, Vacc+) and those vaccinated without having previously shown COVID-19 seroconversion (SERO−, Vacc+), the latter group showing similar titers to the SERO+, Vacc- participants (p=0.166). The median antibody titer in SERO+, Vacc+ patients increased 15-fold following vaccination. Discussion Humoral immunity against SARS-CoV-2 appears to be persistent in elderly institutionalized patients, with a good post-vaccination response by residents who had already shown seroconversion but a notably diminished response by those who were seronegative before vaccination. To evaluate immunity in its entirety and elaborate a sound vaccination strategy, the cellular immune response via T cells specific to SARS-CoV-2 merits analysis, as this response is susceptible to being affected by immunosenescence.

Three Outbreaks of COVID-19 in a Single Nursing Home over Two Years of the SARS-CoV-2 Pandemic

“…This is in contrast to a report showing that SARS-CoV-2 naï ve residents had lower antibody responses to BNT162b2 vaccination than naï ve staff [31]. A French study in a similar setting showed persistent humoral immunity against SARS-CoV-2 in residents, with a post-vaccination response lasting at least nine months in those who were previously infected, and lower in those who were seronegative before vaccination [32]. This is no different than in other age groups since waning of the vaccinal humoral immune response in the absence of re-stimulation is a normal immunological phenomenon and has been well established after vaccination against SARS-CoV-2 [33][34][35], leading to introduction of booster doses.…”

Effectiveness of Vaccination in Preventing COVID-19: A Community Study Comparing Four Vaccines

“…Although a reduced VE in the population aged above 60 was reported [ 24 ], the above-mentioned Hungarian study found the VE in individuals over 65 to be at least as good as in the younger population [ 22 ]. Since the ability to mount an adequate immune response following vaccination has been shown to be well preserved in older adults [ 26 , 27 , 28 ], increased VE in this population may be attributed to decreased exposure to the virus given that older categories of the population are the most inclined to closely follow the required epidemiological measures. Whatever the underlying reason(s), this is just as well since the highest proportion of the population in Serbia had received this vaccine, including in our study group.…”