Humoral immune response after COVID-19 infection or BNT162b2 vaccine among older adults: evolution over time and protective thresholds

Abstract

The objectives of this study were to assess the dynamics of the SARS-CoV-2 anti-RBD-IgG response over time among older people after COVID-19 infection or vaccination and its comparison with indicative levels of protection. Geriatric patients with SARS-CoV-2 serological test results were included and divided into three groups. A vaccine group ( n = 34), a group of natural COVID-19 infection ( n = 32), and a group who contracted COVID-19 less than 15 days after the first injection ( n = 17). Eighty-three patients were included; the median age with IQR was 87 (81–91) years. In the vaccine group at 1 month since the first vaccination, the median titer of anti-RBD-IgG was 620 (217–1874) BAU/ml with 87% of patients above the theoretical protective threshold of 141 BAU/ml according to Dimeglio et al. (J Infec. 84(2):248–88, [ 7 ]). Seven months after the first vaccination, this titer decreased to 30 (19–58) BAU/ml with 9.5% of patients > 141 BAU/ml. In the natural COVID-19 infection group, at 1 month since the date of first symptom onset, the median titer was 798 (325–1320) BAU/ml with 86.7% of patients > 141 BAU/ml and fell to 88 (37–385) with 42.9% of patients > 141 BAU/ml at 2 months. The natural infection group was vaccinated 3 months after the infection. Five months after the vaccination cycle, the median titer was 2048 (471–4386) BAU/ml with 83.3% of patients > 141 BAU/ml. This supports the clinical results describing the decrease in vaccine protection over time and suggests that vaccination after infection can maintain significantly higher antibody titer levels for a prolonged period of time.

What is New in Prophylaxis and Treatment of Covid- 19 in Renal Transplant Patients?

“…Other patients with a weak humoral immune response are older patients. The weak response occurs both after naïve COVID-19 infection and after BNT162b2 vaccination (12). The study also suggests that in these patients, vaccination after infection may be useful because it maintains a higher antibody titer for a large period.…”

“…Several studies (11,12) document the low immunization rate that occurs in several subjects receiving two doses of the mRNA-1273 SARS-CoV-2 vaccine. Among these are kidney transplant recipients as documented by the study of Benotmane et al (11).…”

A systematic review and meta-analysis of the effectiveness and safety of COVID-19 vaccination in older adults

“…Four articles reported on VE (58-61), while three articles reported antibody titer levels after vaccination (55-57) in the elderly. Six articles reported the effectiveness and safety of two vaccine doses (56)(57)(58)(59)(60)(61), while only one article reported the effectiveness and safety of three vaccine doses (55) in elderly people. Five articles reported the effectiveness and safety of the nucleic acid vaccine (56,(58)(59)(60)(61), while three articles reported the effectiveness and safety of the inactivated vaccine (55, 57, 58) in elderly people.…”

“…Six articles reported the effectiveness and safety of two vaccine doses (56)(57)(58)(59)(60)(61), while only one article reported the effectiveness and safety of three vaccine doses (55) in elderly people. Five articles reported the effectiveness and safety of the nucleic acid vaccine (56,(58)(59)(60)(61), while three articles reported the effectiveness and safety of the inactivated vaccine (55, 57, 58) in elderly people. Although vaccination was found to provide clear protection against SARS-CoV-2 infection in older adults, the results showed high and inexplicable heterogeneity in terms of both its effectiveness and its safety.…”

A personalized antibody score for predicting individual COVID-19 vaccine-elicited antibody levels from basic demographic and health information

“…Some studies included only health care workers and did not cover the whole spectrum of the general population, especially older adults and those with underlying medical conditions (4,(9)(10)(11)(12). Most of the other studies targeted at the general population lumped antibody measurements together with different elapsed times since vaccination (12)(13)(14)(15)(16)(17), making precise determination and comparison of individual dynamics difficult.…”