Immunogenicity of the BNT162b2 mRNA COVID-19 vaccine in older residents of a long-term care facility: relation with age, frailty and prior infection status

Abstract

Clinical and biological assessment of the COVID-19 vaccine efficacy in the frail population is of crucial importance. The study focuses on measuring the levels of anti-SARS-CoV-2 IgG antibodies before and after BNT162b2 mRNA COVID-19 vaccination among long-term care facility (LTCF) elderly residents. We conducted a prospective, single-center, observational study among LTCF residents. The study protocol was based on three blood sample acquisitions: first taken at baseline-5 days before the first dose of the vaccine, second-20 days after the first dose, and third-12 days after the second shot of the vaccine. The comparison was made for two cohorts: patients with and without prior COVID-19 infection. The data was collected from January to March 2021. A total number of 78 LTCF residents (55 women and 23 men) aged 62-104, 85.72 ± 7.59 years (mean ± SD), were enrolled in the study. All study participants were investigated for the presence of SARS-CoV-2 anti-spike (S) protein IgG, using a chemiluminescent immunoassay. Frailty was assessed with the Clinical Frailty Scale. Among elderly COVID-19 survivors in LTCF, a single dose of vaccine significantly increased anti-SARS-CoV-2 IgG antibody levels. IgG concentration after a single and double dose was comparable, which may suggest that elderly COVID-19 survivors do not require a second dose of vaccine. For residents without a previous history of COVID-19, two doses are needed to achieve an effective serological response. The level of anti-SARS-CoV-2 IgG antibodies after vaccination with BNT162b2 mRNA COVID-19 did not correlate with the frailty and age of the studied individuals.

Keywords: COVID-19; COVID-19 vaccines; Frailty; Long-term care; Older adults; SARS-CoV-2.

Fig. 1

Study flowchart

Fig. 2

Serological response to the first and the second dose of the BNT162b2 mRNA COVID-19 vaccine in individuals with and without laboratory-confirmed previous SARS-CoV-2 infection (y-axis is log-scaled ln(0.9 + ○) with raw values; whiskers mark mean and location of the 25/75 percentile/IQR) only a group with two doses of vaccine is presented, n = 62. After the first dose, in a group without previous SARS-CoV-2 infection 10 patients were still seronegative. The † symbol marks large effect in the Friedman test whereas corresponding p-values were obtained for the post hoc pairwise Wilcoxon test with Holm–Bonferroni adjustment; the ○ symbol marks large effect in ANOVA test whereas corresponding p-values were obtained for the post hoc pairwise t test with Holm–Bonferroni adjustment

Fig. 3

The effects of the first (blue) and second (red) BNT162b2 mRNA COVID-19 vaccine dose as a difference between anti-S titres noted during consecutive examinations (whiskers mark mean and IQR; y-axis is linear; only a group with two doses of vaccine is presented; n = 62). Lower chart shows the matching anti-S titers, sorted by the last measured level (blue and red denote positive change after, respectively, first and second dose; cases with the level lower after the second dose are colored gray). For clarity, the initial level is additionally marked with x while the final level (observed after second dose) with square. The ◇ symbol denotes a large effect in Kolmogorov–Smirnov test (p < 0.001) and Mann–Whitney test (p = 0.005)