Efficacy of convalescent plasma therapy for COVID-19 in Japan: An open-label, randomized, controlled trial.

BACKGROUND: Convalescent plasma is a potential therapeutic option for patients with coronavirus disease 2019 (COVID-19). Despite its use for treating several viral infections, we lack comprehensive data on its efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: We conducted a multicenter, open-label, randomized controlled trial of convalescent plasma therapy with high neutralizing activity against SARS-CoV-2 in high-risk patients within five days after the onset of COVID-19 symptoms. The primary endpoint was the time-weighted average change in the SARS-CoV-2 viral load in nasopharyngeal swabs from days 0-5. RESULTS: Between February 24, 2021, and November 30, 2021, 25 patients were randomly assigned to either convalescent plasma (n = 14) or standard of care (n = 11) groups. Four patients discontinued their allocated convalescent plasma, and 21 were included in the modified intention-to-treat analysis. The median interval between the symptom onset and plasma administration was 4.5 days (interquartile range, 3-5 days). The primary outcome of the time-weighted average change in the SARS-CoV-2 viral load in nasopharyngeal swabs did not significantly differ between days 0-5 (1.2 log10 copies/mL in the convalescent plasma vs. 1.2 log10 copies/mL in the standard of care (effect estimate, 0.0 [95% confidence interval, -0.8-0.7]; P = 0.94)). No deaths were observed in either group. CONCLUSIONS: The early administration of convalescent plasma with high neutralizing activity did not contribute to a decrease in the viral load within five days compared with the standard of care alone.

Factors associated with anti-SARS-CoV-2 IgG antibody production in patients convalescing from COVID-19.

INTRODUCTION: Among patients with coronavirus disease 2019 (COVID-19), the factors that affect anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody production remain unclear. This study aimed to identify such factors among patients convalescing from COVID-19. METHODS: This study comprised patients who had been diagnosed with COVID-19 between January 1 and June 30, 2020 and gave consent for anti-SARS-CoV-2 spike protein antibody measurement using enzyme-linked immunosorbent assay during their acute and/or convalescent phases. Factors related to elevated antibody titers and the relationship between the days from disease onset and the development of antibody titers were assessed. RESULTS: A total of 84 participants enrolled in the study. Nineteen participants had antibody titers measured during the convalescent phase only, and 65 participants had antibody titers measured during the acute and convalescent phases. The antibody titers peaked in weeks 5 and 6. The stepwise multivariate log-normal analysis revealed that male sex (P = 0.04), diabetes mellitus (P = 0.03), and high C-reactive protein levels during the disease course (P < 0.001) were associated with elevated IgG antibodies. Glucocorticoid use was not associated with antibody titers. CONCLUSION: The study found that high values of maximum CRP levels during the acute phase, male sex, and diabetes mellitus were associated with elevated antibody titers. Antibody titers tended to be highest in the first 5 or 6 weeks after the onset of symptoms.

High diagnostic accuracy of quantitative SARS-CoV-2 spike-binding-IgG assay and correlation with in vitro viral neutralizing activity.

Background: Antibody testing can easily evaluate the clinical status of patients, aid in the diagnosis of multisystem inflammatory syndrome, and monitor the immunity level in the population. However, the applicability of serological tests in detecting antibodies against the severe acute respiratory syndrome 2 (SARS-CoV-2) spike-binding protein remains limited. This study aimed to quantify both serum-derived neutralizing immunoglobulin-G (IgG) antibody activity and the amount of anti-SARS-CoV-2 Spike-IgG (S-IgG) in convalescent sera/plasmas and evaluate the direct correlation between the in vitro IgG-EC50 values and S-IgG values. Methods: We evaluated the neutralizing activity of purified IgG (IgG-EC50), quantified S-IgG in the serum/plasma of consecutive COVID-19 convalescent individuals using a cell-based virus-neutralizing assay, and determined the correlation between IgG-EC50 and S-IgG. In addition, we evaluated rational cut-off values using the receiver operating characteristic (ROC) curve and calculated the sensitivity and specificity of the quantitative S-IgG assay for moderate and high IgG-EC50. Results: A high correlation was observed between S-IgG and IgG-EC50 with a Spearman's ρ value of -0.748 (95 % confidence interval [CI]: -0.804-0.678). Using an IgG-EC50 of 50 µg/mL and 20 µg/mL as the cut-off values for moderate and high in vitro neutralizing activity, respectively, the Youden's index values of 287.5 binding antibody units (BAU)/mL and 454.1 BAU/mL determined from the ROC curve showed the highest diagnostic accuracy, with Kappa values of 0.884 (95 % CI: 0.823-0.946) and 0.920 (95 % CI: 0.681-0.979), respectively. Conclusions: Quantitative S-IgG tests are a useful and convenient tool for estimating in vitro virus-neutralizing activity, with a high correlation with IgG-EC50 when the rational cut-off value is carefully determined.

Trends of participants in convalescent plasma donation for COVID-19 in Japan as the pandemic evolved.

Background: We aimed to investigate chronological changes in the characteristics of participants in a coronavirus disease 2019 convalescent plasma donation study that may benefit optimal collection methods in the future. Methods: Data from a convalescent plasma donation study from April 30, 2020 to November 5, 2021 were collected and analyzed. After August 23, 2021, an interim analysis of factors linked to higher antibody titers led us to restrict our participant recruitment criteria to participants who were within 4 months of disease onset and to patients who were otherwise most likely to have sufficiently high antibody titers. Overall, 1299 samples from 1179 patients were analyzed. Results: Over the duration of the study, 35.9% of the samples were deemed eligible for convalescent plasma collection. The overall eligibility rate initially declined, dipping to <20% after one year. During this period, the proportion of enrolled samples from patients who had severe illness also declined, and the proportion of samples from participants who were >120 days post disease onset increased. After the addition of days from onset and vaccination status to our participant recruitment criteria, the eligibility rate improved significantly. Conclusions: As outbreaks of emerging infectious disease occur, it is desirable to construct and implement a scheme for convalescent plasma donation promptly and to monitor the eligibility rate over time. If it declines, promptly analyze and resolve the associated factors. Additionally, vaccine development and infection prevalence are likely to influence the effective recruitment of participants with high antibody titers.

Risk factors for mental health of Technical Intern Trainees from the Philippines / 国際保健医療

Introduction  The purpose of this study was to identify risk factors related to the mental health of technical intern trainees from the Philippines in Japan, which focus on the relationship between their acculturation strategies and mental health.Method  Mental health, acculturation strategies, acculturative stress, job stress, social support and demographic factors including Japanese language proficiency were used for the variables in the English version of self-administered questionnaire. A total of 180 (115 men, 47 women and 16 gender unreported) Filipino technical intern trainees participated in this study. The data of 132 (95 men, 37 women) participants who completely answered the questionnaires were analyzed.Results  Results showed that gender, marital status, existence of children, Japanese language proficiency, acculturation strategies and acculturative stress were significantly related to the mental health of Filipino technical intern trainees. Results also showed that social support was significantly related to Japanese language proficiency and acculturation strategies for acquisition of Japanese culture. Conclusions  Findings suggest that factors contributing to the worsening of mental health of Filipino technical intern trainees are (a) being male, (b) existence of a child/children, (c) single marital status, (d) low Japanese language proficiency, (e) low acquisition of Japanese culture, and (f) high acculturative stress. Findings also suggest low levels of social support are risk factors related to low Japanese language proficiency and low acquisition of Japanese culture. Support programs for improvement in Japanese language skill and familiarizing with Japanese culture may be an effective way to maintain positive mental health in Filipino technical intern trainees. In addition, an establishment of environment to be able to easily and adequately receive psychological support from their family members living in the Philippines may be important to their mental well-being.

Risk factors for mental health of Technical Intern Trainees from the Philippines / 国際保健医療

Introduction  The purpose of this study was to identify risk factors related to the mental health of technical intern trainees from the Philippines in Japan, which focus on the relationship between their acculturation strategies and mental health.Method  Mental health, acculturation strategies, acculturative stress, job stress, social support and demographic factors including Japanese language proficiency were used for the variables in the English version of self-administered questionnaire. A total of 180 (115 men, 47 women and 16 gender unreported) Filipino technical intern trainees participated in this study. The data of 132 (95 men, 37 women) participants who completely answered the questionnaires were analyzed.Results  Results showed that gender, marital status, existence of children, Japanese language proficiency, acculturation strategies and acculturative stress were significantly related to the mental health of Filipino technical intern trainees. Results also showed that social support was significantly related to Japanese language proficiency and acculturation strategies for acquisition of Japanese culture. Conclusions  Findings suggest that factors contributing to the worsening of mental health of Filipino technical intern trainees are (a) being male, (b) existence of a child/children, (c) single marital status, (d) low Japanese language proficiency, (e) low acquisition of Japanese culture, and (f) high acculturative stress. Findings also suggest low levels of social support are risk factors related to low Japanese language proficiency and low acquisition of Japanese culture. Support programs for improvement in Japanese language skill and familiarizing with Japanese culture may be an effective way to maintain positive mental health in Filipino technical intern trainees. In addition, an establishment of environment to be able to easily and adequately receive psychological support from their family members living in the Philippines may be important to their mental well-being.

The Number of Lives Saved and Quality-adjusted Life Years Prolonged by Ticlopidine Hydrochloride over the Past 20 years in Japan / General Medicine

PURPOSE: Ticlopidine hydrochloride, an antiplatelet agent, is believed to have saved life years in many patients with ischemic cerebral vascular diseases in Japan. But severe adverse events have also been reported. The current investigation aimed to compare two hypothetical cohorts treated with and without ticlopidine in terms of risks and benefits of ticlopidine treatment using Markov model.<BR>METHODS: We conducted Markov decision analysis to estimate the number of lives saved and the increase in quality-adjusted life years (QALYs) over the past 20 years by ticlopidine in Japan. Two cohorts of 60-year-old male patients with previous histories of cerebral infarction, one of which treated with ticlopidine and the other not treated with ticlopidine, were compared with respect to the number of deaths and quality of life (QOL) . Data incorporated were the probabilities of the recurrence of cerebral infarction and the associated mortality, adverse events of the drug, and the utility of health status treated with ticlopidine.<BR>RESULTS: Approximately 1, 630, 000 patients were estimated to be on ticlopidine for variable periods of time during the past 20 years in Japan. With treatment, 17, 130 lives were saved, while 1, 338 patients died because of cerebral bleeding, agranulocytosis, severe hepatic dysfunction, or thrombotic thrombocytic purpura, resulting in a net benefit of 15, 792 lives saved by ticlopidine over the past 20 years. In terms of QOL, there was a total increase of 382, 191 QALYs. Sensitivity analyses showed that the older the patients when ticlopidine therapy was started, the smaller the benefits that were gained by treatment.<BR>CONCLUSIONS: Ticlopidine is considered to have made a great contribution in savingmany lives and improving QALYs in the past 20 years in Japan. This kind of analysis based on Markov model can be employed to demonstrate effectiveness of drugs and medical technologies in terms of population health outcomes.

SARS-CoV-2-neutralizing humoral IgA response occurs earlier but modest and diminishes faster compared to IgG response.

Secretory immunoglobulin A (IgA) plays a crucial role in the mucosal immunity for preventing the invasion of the exogenous antigens, however, little has been understood about the neutralizing activity of serum IgA. Here, to examine the role of IgA antibodies against COVID-19 illnesses, we determined the neutralizing activity of serum/plasma IgG and IgA purified from previously SARS-CoV-2-infected and COVID-19 mRNA-vaccine-receiving individuals. We found that serum/plasma IgA possesses substantial but rather modest neutralizing activity against SARS-CoV-2 compared to IgG with no significant correlation with the disease severity. Neutralizing IgA and IgG antibodies achieved the greatest activity at approximately 25 and 35 days after symptom onset, respectively. However, neutralizing IgA activity quickly diminished and went down below the detection limit approximately 70 days after onset, while substantial IgG activity was observed till 200 days after onset. The total neutralizing activity in sera/plasmas of those with COVID-19 largely correlated with that in purified-IgG and purified-IgA and levels of anti-SARS-CoV-2-S1-binding IgG and anti-SARS-CoV-2-S1-binding IgA. In individuals who were previously infected with SARS-CoV-2 but had no detectable neutralizing IgA activity, a single dose of BNT162b2 or mRNA-1273 elicited potent serum/plasma neutralizing IgA activity but the second dose did not further strengthen the neutralization antibody response. The present data show that the systemic immune stimulation with natural infection and COVID-19 mRNA-vaccines elicit both SARS-CoV-2-specific neutralizing IgG and IgA response in serum, but the IgA response is modest and diminishes faster compared to IgG response. Author SummaryImmunoglobulin A (IgA) is the most abundant type of antibody in the body mostly located on mucosal surfaces as a dimeric secretory IgA. Such secretory IgA plays an important role in preventing the adherence and invasions of foreign objects by its neutralizing activity, while monomeric serum IgA is thought to relate to the phagocytic immune system activation. Here, we report that individuals with the novel coronavirus disease (COVID-19) developed both systemic neutralizing IgG and IgA active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the neutralizing IgA response was quick and reached the highest activity 25 days post-symptom-onset, compared to 35 days for IgG response, neutralizing IgA activity was modest and diminished faster than neutralizing IgG response. In individuals, who recovered from COVID-19 but had no detectable neutralizing IgA activity, a single dose of COVID-19 mRNA-vaccine elicited potent neutralizing IgA activity but the second dose did not further strengthen the antibody response. Our study provides novel insights into the role and the kinetics of serum IgA against the viral pathogen both in naturally-infected and COVID-19 mRNA-vaccine-receiving COVID-19-convalescent individuals.

Association between reactogenicity and SARS-CoV-2 antibodies after the second dose of the BNT162b2 COVID-19 vaccine

High vaccine reactogenicities may reflect stronger immune responses, but the epidemiological evidence for coronavirus disease 2019 (COVID-19) vaccines is sparse and inconsistent. We observed that a fever of [≥]38{square} after two doses of the BNT162b2 vaccine was associated with higher severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike IgG titers.

Highly-Neutralizing COVID-19-Convalescent-Plasmas Potently Block SARS-CoV-2 Replication and Pneumonia in Syrian Hamsters.

Despite various attempts to treat SARS-CoV-2-infected patients with COVID-19-convalescent plasmas, neither appropriate approach nor clinical utility has been established. We examined the efficacy of administration of highly-neutralizing COVID-19-convalescent plasma (hn-plasmas) and such plasma-derived IgG administration using the Syrian hamster COVID-19 model. Two hn-plasmas, which were in the best 1% of 340 neutralizing-activity-determined convalescent plasma samples, were intraperitoneally administered to SARS-CoV-2-infected hamsters, resulting in significant reduction of viral titers in lungs by up to 32-fold as compared to the viral titers in hamsters receiving control non-neutralizing plasma, while with two moderately neutralizing plasmas (mn-plasmas) administered, viral titer reduction was by up to 6-fold. IgG fractions purified from the two hn-plasmas also reduced viral titers in lungs than those from the two mn-plasmas. The severity of lung lesions seen in hamsters receiving hn-plasmas was minimal to moderate as assessed using micro-computerized tomography, which histological examination confirmed. Western blotting revealed that all four COVID-19-convalescent-plasmas variably contained antibodies against SARS-CoV-2 components including the receptor-binding domain and S1 domain. The present data strongly suggest that administering potent-neutralizing-activity-confirmed COVID-19-convalescent plasmas would be efficacious in treating patients with COVID-19. ImportanceConvalescent plasmas obtained from patients, who recovered from a specific infection, have been used as agents to treat other patients infected with the very pathogen. To treat using convalescent plasmas, despite that more than 10 randomized-controlled-clinical-trials have been conducted and more than 100 studies are currently ongoing, the effects of convalescent plasma against COVID-19 remained uncertain. On the other hand, certain COVID-19 vaccines have been shown to reduce the clinical COVID-19 onset by 94-95%, for which the elicited SARS-CoV-2-neutralizing antibodies are apparently directly responsible. Here, we demonstrate that highly-neutralizing-effect-confirmed convalescent plasmas significantly reduce the viral titers in the lung of SARS-CoV-2-infected Syrian hamsters and block the development of virally-induced lung lesions. The present data provide a proof-of-concept that the presence of highly-neutralizing antibody in COVID-19-convalescent plasmas is directly responsible for the reduction of viral replication and support the use of highly-neutralizing antibody-containing plasmas in COVID-19 therapy with convalescent plasmas.

SARS-CoV-2 breakthrough infection during the Delta-dominant epidemic and neutralizing antibodies against Omicron in comparison with the third dose of BNT162b2: a matched analysis

BackgroundLongitudinal data are lacking to compare booster effects of Delta breakthrough infection versus the third vaccine dose on neutralizing antibodies (NAb) against Omicron. MethodsParticipants were the staff of a national research and medical institution in Tokyo who attended serological surveys on June 2021 (baseline) and December 2021 (follow-up); in between, the Delta-dominant epidemic occurred. Of 844 participants who were infection-naive and had received two doses of BNT162b2 at baseline, we identified 11 breakthrough infections during the follow-up. One control matched to each case was randomly selected from those who completed the booster vaccine and those who were unboosted by the follow-up. We used the generalized estimating equation model to compare live-virus NAb against Wuhan, Delta, and Omicron across groups. ResultsPersons who experienced breakthrough infection showed marked increases in NAb titers against Wuhan (4.1-fold) and Delta (5.5-fold), and 64% had detectable NAb against Omicron at follow-up, although the NAb against Omicron after breakthrough infection was 6.7- and 5.2-fold lower than that against Wuhan and Delta, respectively. The increase was apparent only in symptomatic cases and as high as in the third vaccine recipients. In contrast, these titers largely decreased (Wuhan, Delta) or remained undetected (Omicron) at follow-up in infection-naive and unboosted persons. ConclusionsSymptomatic breakthrough infection during the Delta predominant wave was associated with significant increases in NAb against Wuhan, Delta, and Omicron, similar to the third BNT162b2 vaccine. Given the much lower cross-NAb against Omicron than other virus types, however, infection prevention measures must be continued irrespective of vaccine and infection history while the immune evasive variants are circulating. Key pointsSymptomatic, not asymptomatic, SARS-CoV-2 breakthrough infection after the second BNT162b2 vaccination during the Delta-predominant wave enhanced neutralizing antibodies against Wuhan, Delta, and Omicron comparable to the three vaccine doses, although immunity against Omicron was much lower than Wuhan and Delta.

Association study of HLA with the kinetics of SARS-CoV-2 spike specific IgG antibody responses to BNT162b2 mRNA vaccine

BNT162b2, an mRNA-based SARS-CoV-2 vaccine (Pfizer-BioNTech), is one of the most effective COVID-19 vaccines and has been approved by more than 130 countries worldwide. However, several studies have reported that the COVID-19 vaccine shows high interpersonal variability in terms of humoral and cellular responses, such as those with respect to SARS-CoV-2 spike protein immunoglobulin (Ig)G, IgA, IgM, neutralizing antibodies, and CD4+ & CD8+ T cells. The objective of this study is to investigate the kinetic changes in anti-SARS-CoV-2 spike IgG (IgG-S) profiles and adverse reactions and their associations with HLA profiles among 100 hospital workers from the Center Hospital of the National Center for Global Health and Medicine (NCGM), Tokyo, Japan. DQA1*03:03:01 (P = 0.017; Odd ratio (OR) 2.80, 95%Confidence interval (CI) 1.05-7.25) was significantly associated with higher IgG-S production after two doses of BNT162b2 while DQB1*06:01:01:01 (P = 0.028, OR 0.27, 95%CI 0.05-0.94) was significantly associated with IgG-S declines after two doses of BNT162b2. No HLA alleles were significantly associated with either local symptoms or fever. However, C*12:02:02 (P = 0.058; OR 0.42, 95%CI 0.15-1.16), B*52:01:01 (P = 0.031; OR 0.38, 95%CI 0.14-1.03), DQA1*03:02:01 (P = 0.028; OR 0.39, 95%CI 0.15-1.00) and DPB1*02:01:02 (P = 0.024; OR 0.45, 95%CI 0.21-0.97) appeared significantly associated with protection against systemic symptoms after two doses of BNT162b2 vaccination. Further studies with larger sample sizes are clearly warranted to determine HLA allele associations with the production and long-term sustainability of IgG-S after COVID-19 vaccination.

SARS-CoV-2 specific T cell and humoral immune responses upon vaccination with BNT162b2

IntroductionThe humoral and cellular immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) upon coronavirus disease 2019 (COVID-19) vaccination remain to be clarified. Hence, we aimed to investigate the long-term chronological changes in SARS-CoV-2 specific IgG antibody, neutralizing antibody, and T cell responses during and after receiving the BNT162b2 vaccine. MethodsWe performed serological, neutralization, and T cell assays among 100 hospital workers aged 22-73 years who received the vaccine. We conducted seven surveys up to eight months after the second vaccination dose. ResultsSARS-CoV-2 spike protein-specific IgG (IgG-S) titers and T cell responses increased significantly following the first vaccination dose. The highest titers were observed on day 29 and decreased gradually until the end of the follow-up period. There was no correlation between IgG-S and T cell responses. Notably, T cell responses were detected on day 15, earlier than the onset of neutralizing activity. ConclusionsThis study demonstrated that both IgG-S and T cell responses were detected before acquiring sufficient levels of SARS-CoV-2 neutralizing antibodies. These immune responses are sustained for approximately six-ten weeks but not for seven months or later following the second vaccination, indicating the need for the booster dose (i.e., third vaccination).

COVID-19 breakthrough infections and pre-infection neutralizing antibody

BackgroundWhile increasing coverage of effective vaccines against coronavirus disease 2019 (COVID-19), emergent variants raise concerns about breakthrough infections. Data are limited, however, whether breakthrough infection during the epidemic of the variant is ascribed to insufficient vaccine-induced immunogenicity. MethodsWe described incident COVID-19 in relation to the vaccination program among workers of a referral hospital in Tokyo. During the predominantly Delta epidemic, we followed 2,473 fully vaccinated staff (BNT162b2) for breakthrough infection and selected three matched controls. We measured pre-infection neutralizing antibodies against the wild-type, Alpha (B.1.1.7), and Delta (B.1.617.2) strains using live viruses and anti-spike antibodies using quantitative assays, and compared them using the generalized estimating equation model between the two groups. ResultsNo COVID-19 cases occurred 1-2 months after the vaccination program during the fourth epidemic wave in Japan, dominated by the Alpha variant, while 22 cases emerged 2-4 months after the vaccination program during the fifth wave, dominated by the Delta variant. In the vaccinated cohort, all 17 cases of breakthrough infection were mild or asymptomatic and had returned to work early. There was no measurable difference between cases and controls in pre-infection neutralizing antibody titers against the wild-type, Alpha, and Delta, and anti-spike antibody titers, while neutralizing titers against the variants were considerably lower than those against the wild-type. ConclusionsPre-infection neutralizing antibody titers were not decreased among patients with breakthrough infection under the Delta variant rampage. The result points to the importance of infection control measures in the post-vaccination era, irrespective of immunogenicity profile.

Neutralizing antibodies following three doses of BNT162b2 vaccine, breakthrough infection, and symptoms during the Omicron predominant wave

BackgroundData on the role of immunogenicity following the third vaccine dose against Omicron infection and coronavirus disease 2019 (COVID-19)-compatible symptoms of infection are limited. MethodsFirst we examined vaccine effectiveness (VE) of the third-dose against the second dose during the Omicron wave among the staff at a tertiary hospital in Tokyo. In a case-control study of a cohort of third vaccine recipients, we compared the pre-infection levels of live-virus neutralizing antibodies (NAb) against Omicron between breakthrough cases and their controls, who had close contact with COVID-19 patients. Among these cases, we examined the association between pre-infection NAb levels and the number of COVID-19-compatible symptoms experienced during the Omicron wave. ResultsAmong the 1456 participants for VE analysis, 60 (4%) breakthrough infections occurred during the Omicron wave (January to March 2022). The third-dose VE for infection, relative to the second dose was 54.6% (95% CI: 14.0-76.0). Among the recipients of the third vaccine, pre-infection NAb levels against Omicron did not significantly differ between the cases and controls. Among the cases, those who experienced COVID-19-compatible symptoms had lower pre-infection NAb levels against Omicron than those who did not. ConclusionsThe third vaccine dose was effective in decreasing the risk of severe acute respiratory syndrome coronavirus 2 infection during the Omicron wave compared with the second dose. Among third-dose recipients, higher pre-infection NAb levels may not be associated with a lower risk of Omicron infection. Contrarily, they may be associated with fewer symptoms of infection. SummaryThe third vaccine dose reduced SARS-CoV-2 infection risk during the Omicron wave. Higher neutralizing antibody levels may not reduce Omicron infection risk in third-dose patients. On the contrary, it may be associated with fewer symptoms of infection.

Correlates of Neutralizing/SARS-CoV-2-S1-binding Antibody Response with Adverse Effects and Immune Kinetics in BNT162b2-Vaccinated Individuals

BackgroundWhile mRNA vaccines against SARS-CoV-2 have been exceedingly effective in preventing symptomatic viral infection, the features of immune response remain to be clarified. MethodsIn 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. FindingsSignificant 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. InterpretationBNT162b2-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. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWhile mRNA vaccines against SARS-CoV-2 have been exceedingly effective in preventing symptomatic viral infection, the salient features of immune response including the persistence of protection remain to be clarified. There is a report that anti-SARS-CoV-2 antibodies persist through 6 months after the second dose of mRNA-1273 vaccine (Doria-Rose et al. N Engl J Med. 2021;384:2259-2261); however, more definite immune kinetics following mRNA-vaccine-elicited protection have to be clarified. The mRNA-vaccine-elicited protection against SARS-CoV-2 variants are also to be determined. Added value of this studyIn the present prospective study, 225 twice-BNT162b2-dose-receiving individuals in Japan were enrolled. No significant correlation was seen between 50% neutralizing titers (NT50s), determined by using infectious SARS-CoV-2 virions and live target cells, and adverse effects. Largely, NT50s and IgG levels were greater in women than in men. Following 28 days post-2nd shot, significant reduction was seen in NT50s, IgG, and IgM levels. The average half-life of NT50s was [~]68 days and the average time-length for participants serums to lose the detectable activity was [~]198 days. Although serums from elite-responders potently to moderately blocked the infectivity of variants of concerns, some serums with moderate NT50s failed to block the infectivity of a beta strain. Implications of all the available evidenceBNT162b2 efficacy is likely to be diminished to under detection limit by 6-7 months post-1st shot on average. Individuals with moderate NT50s may fail to block beta variants. If BNT162b2-elicited immune memory is lost soon, additional vaccine(s) or other protective means would be needed.