Assessment of the Humoral Immune Response Following COVID-19 Vaccination in Healthcare Workers: A One Year Longitudinal Study

Abstract

The continuous variability of SARS-CoV-2 and the rapid waning of specific antibodies threatens the efficacy of COVID-19 vaccines. We aimed to evaluate antibody kinetics one year after SARS-CoV-2 vaccination with an mRNA vaccine in healthcare workers (HCW), with or without a booster. A marked decline in anti-Spike(S)/Receptor Binding Domain (RBD) antibody levels was registered during the first eight months post-vaccination, followed by a transitory increase after the booster. At three months post-booster an increased antibody level was maintained only in HCW vaccinated after a prior infection, who also developed a higher and long-lasting level of anti-S IgA antibodies. Still, IgG anti-nucleocapsid (NCP) fades five months post-SARS-CoV-2 infection. Despite the decline in antibodies one-year post-vaccination, 68.2% of HCW preserved the neutralization capacity against the ancestral variant, with a decrease of only 17.08% in the neutralizing capacity against the Omicron variant. Nevertheless, breakthrough infections were present in 6.65% of all participants, without any correlation with the previous level of anti-S/RBD IgG. Protection against the ancestral and Omicron variants is maintained at least three months after a booster in HCW, possibly reflecting a continuous antigenic stimulation in the professional setting.

Kinetics of dried blood spot-measured anti-SARS-CoV2 Spike IgG in mRNA-vaccinated healthcare workers

“…Our data strengthen previous findings demonstrating that immunization to SARS-CoV2 through vaccination induces a peak in antibody response soon after vaccination, followed by a marked and progressive decline of anti-Spike IgG antibodies during a 9 months period after vaccination (Levin et al, 2021;Chivu-Economescu et al, 2022).…”

“…The booster dose induced a transitory increase in humoral response, restoring antibody levels to the initial values yielded by primary vaccination (Chivu-Economescu et al, 2022;Desmecht et al, 2022), particularly in naïve individuals (never infected). Even more, heterologous vaccination (primary vaccination with Comirnaty vaccine followed by Spikevax booster) elicited higher anti-SARS-CoV2 antibodies response with respect to homologous (Comirnaty/ Comirnaty) vaccination regimens, confirming literature data (Naito et al, 2022).…”

The Influence of Booster Shot and SARS-CoV-2 Infection on the Anti-Spike Antibody Concentration One Year after the First COVID-19 Vaccine Dose Administration

“…Of note, as much as 82% of the participants decided to receive a booster shot of the Comirnaty vaccine. A similar percentage (70%) has been reported by Chivu-Economescu et al [ 25 ], which proves a high level of confidence in the immunity conferred by the COVID-19 vaccination.…”

“…Lee et al have also reported a higher level of anti-S antibodies 4 months after booster in subjects infected with SARS-CoV-2 within this period in comparison to the boosted participants without SARS-CoV-2 infection. The phenomenon named hybrid immunity—stemming from combined vaccination and infection, has been linked to a higher protection against SARS-CoV-2 and its variants, and explained by the induction of more broadly neutralizing antibodies and a stronger cellular immune response [ 25 , 29 , 30 ]. Lee at al.…”

“…We found that the time passing after the booster influenced the antibody concentration—there was weak, but statistically significant negative correlation between these two variables. Some reports have already been published on the waning vaccine effectiveness against COVID-19 with time since boosting [ 36 ] and a quick antibody level decrease after the booster vaccination [ 23 , 25 , 29 ]. For example, in a study by Ogric et al, anti-S1 SARS-CoV-2 IgG concentration decreased 2.5x between measurements 3 weeks and 3 months after the booster in naïve vaccinees.…”