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Updated: Oct 15, 2025
Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19
Published on: February 16, 2022
Single BNT162b2 vaccine dose produces seroconversion in under 60 s cohort
Yael Shachor-Meyouhas1, Khetam Hussein2, Moran Szwarcwort-Cohen3
1Pediatric Infectious Diseases Unit, Ruth Rappaport Children's Hospital, Rambam Health Care Campus, Haifa, Israel; Management, Rambam Health Care Campus, Haifa, Israel; The Ruth & Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
Introduction:
The coronavirus disease 2019 (COVID-19) pandemic has led to worldwide vaccination development efforts. In December 2020 the Pfizer BNT162b2 vaccine was approved in the United States. This study describes the first BNT162b2 vaccine dose effect on a large cohort.
Methods:
This retrospective study examined first vaccine dose effect on serology and investigated the associations between seroconversion and age or sex.
Results:
Serological blood tests were performed on 1898 participants following first vaccine dose; 81% were tested on day 21, before receiving the second dose (mean age 47.5 ± 12.45; median 47.7, range 18-90). Positive serology was found in 92.7% of day 21 tests. Overall positivity was 86.8%, with rates increasing from 2.5% within 1-14 days to 89.8% (14-20 days), 92.7% (21 days), and 95.9% (>21 days). Mean antibody levels 21 days after first dose were 64.3 ± 33.01 AU/ml, (range 15-373 AU/ml, median 61 AU/ml). Seropositivity was greater in females than males (88.3%. vs 83.3% respectively, p < 0.001; OR1.515; 95% CI 1.152-1.994). Older age > 60 years was associated with decreased likelihood of seropositivity (p < 0.001; OR 0.926; 95% CI 0.911-0.940). Longer time between first vaccination and serology tests was associated with increased likelihood for seropositivity (p < 0.001; OR 1.350; 95% CI 1.298-1.404).
Conclusions:
The high seroconversion rate following first BNT162b2 dose among individuals < 60 may justify delayed delivery of the second dose, potentially help relieve the worldwide vaccination supply shortage, enable vaccination of twice this population within a shorter period, and ultimately reduce COVID-19 contagion.
