Monitoring of SARS-CoV-2 Specific Antibodies after Vaccination

Abstract

Vaccination is considered the most important measure to control the COVID-19 pandemic. Extensive follow-up studies with distinct vaccines and populations are able to promote robust and reliable data to better understand the effectiveness of this pharmacologic strategy. In this sense, we present data regarding binding and neutralizing (achieved by surrogate ELISA assay) antibodies throughout time, from vaccinated and previously infected (PI) health care workers (HCW) in Portugal. We analyzed serum samples of 132 HCW, who were vaccinated and with previous SARS-CoV-2 infection. Samples were collected before vaccination (baseline, M1), at second dose vaccine uptake (M2), and 25–70 days (M3) and 150–210 days (M4) after the second dose for vaccinated individuals. The IgG (anti-RBD/S) antibody geometric mean titers found on vaccinated HCW at M2 (GM = 116.1 BAU/mL; CI: 92.3–146.1) were significantly higher than those found on PI HCW at recruitment (M1) (GM = 35.9 BAU/mL; CI:15.4–83.4), and the neutralizing antibodies (nAb) were similar between these groups, of 93.2 UI/mL (95% CI 73.2–118.5) vs. 84.1 UI/mL (95% CI 40.4–155.9), respectively. We detected around 10-fold higher IgG (anti-RBD/S) antibodies titers in M3 when compared with M2, with a slight but significant decrease in titers from 36 days after the second dose vaccine uptake. The increase of nAb titers was correlated with IgG (anti-RBD/S) antibodies titers; however, in contrast to IgG (anti-RBD/S) antibodies titers, we did not detect a decrease in the nAb titer 36 days after a second vaccine dose uptake. At M4, a decrease of 8-fold in binding IgG (anti-RBD/S) and nAb was observed. No significant differences in antibody titers were observed by sex, age or chronic diseases. Our results suggest that IgG (anti-RBD/S) antibodies titers and nAb titers could be correlated, but an ongoing follow up of the cohort is required to better understand this correlation, and the duration of the immune response.

Seroprevalence of Specific SARS-CoV-2 Antibodies during Omicron BA.5 Wave, Portugal, April–June 2022

“…Antibody levels were lower among those at the extremes of age distribution. This finding may be related to the course of the vaccination campaign and age-related immunosenescence Lower antibody levels in children may be associated with postinfection immunity; antibody levels that were lower after infection than after vaccination have been reported (14,15). Furthermore, at the time of data collection, a booster was not recommended for the pediatric population, which may also explain lower antibody levels.…”

“…Lower antibody levels in children may be associated with postinfection immunity; antibody levels that were lower after infection than after vaccination have been reported ( 14 , 15 ). Furthermore, at the time of data collection, a booster was not recommended for the pediatric population, which may also explain lower antibody levels.…”

“…This finding may be related to the course of the vaccination campaign and age-related immunosenescence. Since September 2021, the first booster vaccinations were rolled out by age criteria; those in the older age groups were vaccinated earlier and experienced a more pronounced wane of antibody levels ( 15 ) compared with middle-aged adults who were vaccinated more recently. Although starting May 15, 2022, a second booster was offered for persons > 80 years of age and for institutionalized persons, our results have not yet reflected the effect of that change.…”

Immunogenicity evaluation after BNT162b2 booster vaccination in healthcare workers

“…Besides their privileged scientific value, these assesements were acutely demanded by the actual pandemic framework, when the whole flow of research, production, authorizing and use of the vaccines against COVID-19 was carried out at a rapid pace. Screening of vaccinated individuals represents a valuable tool for unravel the type and duration of the protective immune response, and for estimating the necessity of a booster dose, helping thus the health decision authorities in implementing important actions for controlling the pandemic and improve the vaccination scheme 39 . At least for a while, screening humoral immune response in vaccinated and infected people is very important to assess persistence of immunity in COVID-19, and evaluate the protective power of the SARS-CoV-2 antibodies 40 .…”

“…At least for a while, screening humoral immune response in vaccinated and infected people is very important to assess persistence of immunity in COVID-19, and evaluate the protective power of the SARS-CoV-2 antibodies 40 . In particular, serological testing could best catch the time-point when protective antibody levels begin to decrease and therefore this test should be included into vaccine effectiveness studies 39 . Thus, within the tested methods, the ELISA-related methodologies remain the most reliable and sensitive ones to evaluate the appeareance of specific antibodies 41 .…”