In a recent study, researchers evaluated the impact of virus-neutralizing antibody (vnAb) titers against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) knowledge on deciding the timing of booster vaccination and social behavior.
Introduction
The global spread of coronavirus disease 2019 (COVID-19) has led to significant morbidity and mortality. To control the pandemic, vaccines have been developed that confer immune protection by antibody generation in the host. The vnAb titers are the most robust serological correlates of immune protection against SARS-CoV-2 infections.
Most clinically approved antibody tests qualitatively detect antibodies that bind to viral proteins. The qualitative measurement of vnAbs, the antibodies that most significantly correlated with infection prevention, is lacking.
Study
In the present study, the researchers conducted a retrospective survey-based study to ascertain the impact of vnAb titer awareness on decisions related to booster vaccine timing and social interactions.
Complimentary IMMUNO-COV tests were offered to employees of two companies between January 1, 2021, and December 4, 2021. Data regarding their age, gender, dates of first, second, and booster vaccination, and the vaccine(s) administered were obtained.
Blood samples were collected from the participants post-vaccination on self-chosen dates and subjected to IMMUNO-COV analysis for the quantification of their vnAb titers against SARS-CoV-2 Delta and Wuhan strains. The employees were asked to voluntarily fill out a questionnaire for assessing the impact of knowing their vnAb titers on deciding booster dose timing and social conduct.
Based on the information obtained and the IMMUNO-COV test results, the team evaluated the rate of vnAb decay, vnAb alterations post booster dose, and the association between age and vnAb titers. The collection days post booster vaccination or a new SARS-CoV-2 infection were excluded from the assessment of vnAb decay kinetics.
The IMMUNO-COV titers were calibrated to International Standard (IU/mL) based on World Health Organization (WHO) to facilitate cross-comparison with published studies. For easier understanding and interpretation of the vnAb titers, historical IMMUNO-COV values were inserted into models of protection reported by Khoury et al. that predict an individual’s protection level against SARS-CoV-2 infections.
Results and Discussion
A total of 214 blood samples were obtained from 56 employees after primary vaccination. All the participants were either double vaccinated with the mRNA-1273 vaccine (Moderna) or the BNT162b2 vaccine (Pfizer-BioNTech) or single vaccinated with Ad26.CoV2.S vaccine (Janssen) vaccine. Moreover, 66% (37/56) of employees received a booster dose of Ad26.CoV.S (2/37), BNT162b2 (32/37), or mRNA-1273 (3/37) within five months post-initial vaccination.
The vnAb titers initially rose after the initial vaccination and declined rapidly thereafter. However, excluding titers that increased after booster doses or new infections, 29 of 52 (56%) employees had vnAb titers constantly exceeding 200 IU/mL up to half a year after initial vaccination. This indicates substantial (exceeding 75%) protection levels against Wuhan strain but a lower (50%) protection level against the Delta variant.
Booster vaccinations were received by 37 of 56 (66%) participants and caused a 60.2-fold increase in vnAb titers. In 23 of 24 (96%) participants, boosted vnAb titers peaked above 900 IU/mL. The pattern of initial vnAb titer increase followed by decrease may be due to an initial outburst of antibody-secreting host cells followed by immune regulation by long-term B cells.
The vnAb decay half-lives averaged about 1.7 months and 2.2 months for the initial two-four-month and four-six-month periods, respectively, and declined to 1.6 months during the six-eight-month period after vaccination. The average age of employees that consistently maintained vnAb titers above 200 IU/mL was 36 years, lower than the average employee age with lower vnAb titers (44 years). This indicates that vnAb levels decrease with advancing age.
Most participants (66%) indicated that knowing their vnAb titer had a moderate to significant impact on their social interactions and decision-making regarding the timing of booster vaccination.
Conclusion
The study findings indicate that vnAb awareness positively impacts an individual’s decision on booster vaccination timing and their social behavior.
Future studies with larger sample sizes, sample stratification, uniform time intervals between vaccination and serological testing should focus on comparing vnAb decay rates post-vaccination with different vaccines.
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