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Abstract
Background: While mRNA vaccines against SARS-CoV-2 have been exceedingly effective in preventing symptomatic viral infection, the features of immune response remain to be clarified.Methods: In the present prospective observational study, 225 healthy individuals in Kumamoto General Hospital, Japan, who received two BNT162b2 doses in February 2021, were enrolled. Correlates of BNT162b2-elicited SARS-CoV-2-neutralizing activity (50% neutralization titer: NT50; assessed using infectious virions and live target cells) with SARS-CoV-2-S1-binding-IgG and -IgM levels, adverse effects (AEs), ages, and genders were examined. The average half-life of neutralizing activity and the average time length for the loss of detectable neutralizing activity were determined and the potency of serums against variants of concerns was also determined.Findings: Significant rise in NT50s was seen in serums on day 28 post-1st dose. A moderate inverse correlation was seen between NT50s and ages, but no correlation was seen between NT50s and AEs. NT50s and IgG levels on day 28 post-1st dose and pain scores following the 2nd shot were greater in women than in men. The average half-life of neutralizing activity in the vaccinees was approximately 67.8 days and the average time length for their serums to lose the detectable neutralizing activity was 198.3 days. While serums from elite-responders (NT50s >1,500-fold: the top 4% among all participants’ NT50s) potently to moderately blocked the infectivity of variants of concerns, some serums with moderate NT50s failed to block the infectivity of a beta strain.Interpretation: BNT162b2-elicited immune response has no significant association with AEs. BNT162b2-efficacy is likely diminished to under detection limit by 6-7 months post-1st shot. High-level neutralizing antibody-containing serums potently to moderately block the infection of SARS-CoV-2 variants; however, a few moderate-level neutralizing antibody-containing serums failed to do so. If BNT162b2-elicited immunity memory is short, an additional vaccine or other protective measures would be needed.Funding Information: This research was supported in part by a grant from the Japan Agency for Medical Research and Development to Maeda (grant number JP20fk0108260, 20fk0108502) and to Mitsuya (grant number 20fk0108502), and in part by a grant for MHLW Research on Emerging and Re-emerging Infectious Diseases and Immunization Program to Maeda (grant number JPMH20HA1006) from Ministry of Health, Labor and Welfare, and in part by a grant for COVID-19 to Mitsuya (grant number 19A3001) and Maeda (grant number 20A2003D) from the Intramural Research Program of National Center for Global Health and Medicine, and in part by the Intramural Research Program of the Center for Cancer Research, National Cancer Institute, National Institutes of Health (Mitsuya).Declaration of Interests: Matsushima, Noda, Sato, and Yoshida are employees of SysmexCorporation.Other authors declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest.Ethics Approval Statement: The Ethics Committees from the Kumamoto General Hospital and NCGM approved this study (Kumamoto General Hospital No. 180, and NCGM-G-004176-00, respectively). Each participant provided a written informed consent, and this study abided by the Declaration of Helsinki principles.
Highlights
Since the emergence of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, the disease quickly spread to the world
There was a high positive correlation of the NT50 values with S1-bindingIgG levels (Spearman’s ρ = 0.71; 95% CI 0.63 to 0.77) as examined on day 28 post-1st shot, while there was only a low positive correlation of the NT50 values with S1-binding-IgM levels (Spearman’s ρ = 0.43; 95% CI 0.31 to 0.53), suggesting that the neutralizing activity largely resides in IgG fraction of the serum of vaccinated participants around on day 28 post-1st shot
Three serums from the moderate responders showed only marginal activity against SARS-CoV-2TY8 − 612. Two of those three samples had no detectable inhibitory activity against SARS-CoV-2TY8 − 612 (Fig. 4). In this prospective observational study, 225 healthy individuals [physicians (n = 36), nurses (n = 125), and other healthcare professionals (n = 64)], who received two doses of 30 μg BNT162b2 (Pfizer–BioNTech) vaccine in February 2021, were enrolled, and the correlates of neutralization activity represented by 50% neutralization titers (NT50) determined by employing the target living VeroE6TMPRSS2 cells and live SARSCoV-2 with ages, adverse effects (AEs) that occur often such as injection-site pain and systemic fever were examined
Summary
Since the emergence of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, the disease quickly spread to the world. The development of vaccines against SARS-CoV-2 was achieved time- and efficacy-wise beyond our expectations within a single calendar year from the availability of the viral sequence to the initiation of immunization of many people in several countries [6,7]. Inactivated vaccines or viral vector vaccines have been available in certain countries and areas [5,7,9,10]. The adenovirus-vector-based vaccine (ChAdOx1 nCoV-19/AZD1222) has reportedly achieved 62% efficacy in initial trials 11. The phase 3 reports of another adenovirus-based vaccine (Ad26.COV2.S) has indicated 85% efficacy against severe disease or death [12,13]
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