Hybrid immunity against reinfection with SARS-CoV-2 following a previous SARS-CoV-2 infection and single dose of the BNT162b2 vaccine in children and adolescents: a target trial emulation.

BACKGROUND: Although most children and adolescents have had a previous SARS-CoV-2 infection and many continue to receive COVID-19 vaccinations, studies of the effectiveness of hybrid immunity against reinfection with the omicron (B.1.1.529) variant are scarce. We aimed to examine the effectiveness of vaccination in convalescent children and adolescents against reinfection with the delta (B.1.617.2) variant and the BA.1 and BA.2 and BA.4 and BA.5 omicron subvariants. METHODS: This retrospective cohort study was devised to emulate a target randomised control trial using a retrospective dataset of anonymised health records of children (5-11 years old) and adolescents (12-16 years old) who were members of the Maccabi Healthcare Services, Israel. The design emulated 91 randomised trials by devising a series of multiple nested trials, compiling the results into a single dataset, and fitting Cox proportional hazards models to estimate adjusted hazard ratios (HRs) with 95% CIs of each measured outcome. The primary aim was to assess the protection from reinfection with the delta variant and the BA.1 and BA.2 and BA.4 and BA.5 omicron subvariants associated with hybrid immunity as a result of a previous SARS-CoV-2 infection followed by vaccination with the BNT162b2 (Pfizer-BioNTech) vaccine. FINDINGS: Data from between from March 1, 2020, to July 31, 2022, for 163 812 individuals (120 721 children [59 404 girls and 61 317 boys], median age 8·0 years [IQR 6·7 to 10·2]; and 43 091 adolescents [21 239 girls and 21 852 boys], median age 13·5 years [12·6 to 14·8]) were included in at least one trial. A single dose of the BNT162b2 vaccine in convalescent children and adolescents confers statistically significant protection against the delta variant (78% [95% CI 72 to 83] in adolescents and 64% [3 to 87] in children) and the omicron BA.1 and BA.2 subvariants (54% [50 to 57] in adolescents and 71% [67 to 73] in children) compared with children who had a previous infection but were unvaccinated. However, the vaccine was not found to confer statistically significant protection against the BA.4 and BA.5 omicron subvariants in adolescents (8% [-18 to 29]) and children (12% [-6 to 27]). INTERPRETATION: Decision makers in BA.4 and BA.5 dominant regions should re-examine whether convalescent individuals aged 5-16 years should receive the BNT162b2 vaccine to prevent future reinfection, especially in light of reports that show that most children and adolescents have already been infected with SARS-CoV-2. FUNDING: None.

Dynamics of Naturally Acquired Immunity Against Severe Acute Respiratory Syndrome Coronavirus 2 in Children and Adolescents.

OBJECTIVE: To evaluate the duration of protection against reinfection conferred by a previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children and adolescents. STUDY DESIGN: We applied 2 complementary approaches: a matched test-negative, case-control design and a retrospective cohort design. A total of 458 959 unvaccinated individuals aged 5-18 years were included. The analyses focused on the period July 1, 2021, to December 13, 2021, a period of Delta variant dominance in Israel. We evaluated 3 SARS-CoV-2-related outcomes: documented polymerase chain reaction-confirmed infection or reinfection, symptomatic infection or reinfection, and SARS-CoV-2-related hospitalization or death. RESULTS: Overall, children and adolescents who were previously infected acquired durable protection against reinfection with SARS-CoV-2 for at least 18 months. Importantly, no SARS-CoV-2-related deaths were recorded in either the SARS-CoV-2-naïve group or the previously infected group. The effectiveness of naturally acquired immunity against a recurrent infection reached 89.2% (95% CI, 84.7%-92.4%) at 3-6 months after the first infection and declined slightly to 82.5% (95% CI, 79.1%-85.3%) by 9-12 months after infection, with a slight nonsignificant waning trend seen up to 18 months after infection. Additionally, children aged 5-11 years exhibited no significant waning of naturally acquired protection throughout the outcome period, whereas waning protection in those aged 12-18 years was more prominent but still mild. CONCLUSIONS: Children and adolescents who were previously infected with SARS-CoV-2 remain protected to a high degree for 18 months. Further research is needed to examine naturally acquired immunity against Omicron and newer emerging variants.

BNT162b2 mRNA Vaccine Effectiveness Given Confirmed Exposure: Analysis of Household Members of Coronavirus Disease 2019 Patients.

BACKGROUND: Although BNT162b2 vaccine-efficacy analyses have been published, the effectiveness of the vaccine in preventing coronavirus disease 2019 given confirmed exposure has not been previously demonstrated, even though it has policy implications, such as the need for self-quarantine when exposure has occurred. METHODS: In a retrospective cohort study, we used data collected between 20 December 2020 and 17 March 2021 from the second largest healthcare provider in Israel to analyze the probability of an additional household infection occurring within 10 days after an index infection. In model 1, vaccine effectiveness was described for Fully Vaccinated individuals (7 or more days from second dose) vs either Unvaccinated individuals or those Recently Vaccinated Once (0-7 days from the first dose, presumably still unprotected). Secondary analyses included correction for differing testing rates. In model 2, we conducted a separate analysis of households comprised of only adults with the same vaccination status. RESULTS: A total of 173 569 households were included, of which 6351 had an index infection (mean [standard deviation] age, 58.9 [13.5] years); 50% were women. Adjusted vaccine effectiveness of Fully Vaccinated compared with Unvaccinated participants was 80.3% (95% confidence interval [CI], 73.5-85.4) and 82.0% (95% CI, 75.6-86.8) compared with those Recently Vaccinated Once. CONCLUSIONS: The BNT162b2 vaccine is effective in high-risk real-life exposure scenarios, but the protection afforded in these settings is lower than that previously described. Individuals with a confirmed significant exposure to severe acute respiratory syndrome are still at risk of being infected even if fully vaccinated.

The Incidence of SARS-CoV-2 Reinfection in Persons With Naturally Acquired Immunity With and Without Subsequent Receipt of a Single Dose of BNT162b2 Vaccine : A Retrospective Cohort Study.

BACKGROUND: There is insufficient evidence regarding the magnitude and durability of protection conferred by a combined effect of naturally acquired immunity after SARS-CoV-2 infection and vaccine-induced immunity. OBJECTIVE: To compare the incidence rate of SARS-CoV-2 reinfection in previously infected persons to that of previously infected persons who subsequently received a single dose of BNT162b2 messenger RNA vaccine. DESIGN: A retrospective cohort study emulating a randomized controlled target trial through a series of nested trials. SETTING: Nationally centralized database of Maccabi Healthcare Services, Israel. PARTICIPANTS: Persons with documented SARS-CoV-2 infection who did not receive subsequent SARS-CoV-2 vaccination were compared with persons with documented SARS-CoV-2 infection who received a single dose of the BNT162b2 vaccine at least 3 months after infection. INTERVENTION: Forty-one randomized controlled trials were emulated, in which 107 413 Maccabi Healthcare Services' members aged 16 years and older were eligible for at least 1 trial. MEASUREMENTS: SARS-CoV-2-related outcomes of infection, symptomatic disease, hospitalization, and death, between 2 March and 13 December 2021. RESULTS: A statistically significant decreased risk (hazard ratio, 0.18 [95% CI, 0.15 to 0.20]) for reinfection was found among persons who were previously infected and then vaccinated versus those who were previously infected but remained unvaccinated. In addition, there was a decreased risk for symptomatic disease (hazard ratio, 0.24 [CI, 0.20 to 0.29]) among previously infected and vaccinated persons compared with those who were not vaccinated after infection. No COVID-19-related mortality cases were found. LIMITATION: Hybrid protection against non-Delta variants could not be inferred. CONCLUSION: Persons previously infected with SARS-CoV-2 gained additional protection against reinfection and COVID-19 from a subsequent single dose of the BNT162b2 vaccine. Nonetheless, even without a subsequent vaccination, reinfection appeared relatively rare. PRIMARY FUNDING SOURCE: None.

Pregnancy outcomes after SARS-CoV-2 infection by trimester: A large, population-based cohort study.

OBJECTIVES: Data regarding women infected with SARS-CoV-2 during early trimesters are scarce. We aimed to assess preterm birth (PTB) and small-for-gestational-age (SGA) rates in a large and unselected cohort by trimester at infection and overall. DESIGN: A retrospective cohort study including all women with a positive SARS-CoV-2 RT-PCR test during a non-ectopic singleton pregnancy between February 21st 2020 and July 2nd 2021 (N = 2753). Each infected woman was matched to a non-infected pregnant woman by age, last menstruation date, sector, and socioeconomic status. METHODS: Logistic regression was conducted to assess the risks of PTB and SGA including an interaction between group and trimester of infection. Multivariable models included underlying diseases, previous abortions and null parity. Subgroup analyses were conducted on symptomatic infected women and matched non-infected women. RESULTS: A total of 2753 /2789 (98.7%) eligible women that were infected during pregnancy could be matched, among them, 17.4% and 48.4% were infected during the first and third trimesters, respectively. While first and second trimester infections were not associated with PTB (p>0.8), third trimester infections and in particular after 34 weeks of gestation had a greater risk of PTB with adjusted ORs of 2.76 (95% CI 1.63-4.67) and 7.10 (95% CI 2.44-20.61), respectively. PTB risk was further heightened in symptomatic third trimester infections (OR = 4.28, 95% CI 1.94-9.25). SGA risk was comparable between study groups across all trimesters of infection. Pregnancy loss incidence was similar in both groups (adjusted OR = 1.16; 95% CI 0.90-1.50). CONCLUSION: SARS-CoV-2 infection was associated with increased risk of PTB only among women infected during late pregnancy, particularly among symptomatic women.

Dynamics in COVID-19 symptoms during different waves of the pandemic among children infected with SARS-CoV-2 in the ambulatory setting.

The aim of this real-life, big data population-based study was to evaluate differences in symptomatic presentation of children infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) between the third and fourth waves of the pandemic in Israel, dominated by the Alpha and Delta variants, respectively. Our cohort included all children and adolescents, members of the second-largest Health Maintenance Organization in Israel that had positive real-time polymerase chain reaction (RT-PCR) test during the third and fourth waves of the pandemic (December 1, 2020, to April 30, 2021, and June 1, 2021, to October 10, 2021, respectively). A total of 32,485 and 44,130 children and adolescents in the third and fourth waves were included in the final analysis. The rate of children with symptomatic disease among patients with documented SARS-CoV-2 infection was higher in the fourth wave compared to the third wave (49.9% vs. 37.5%). The most commonly reported symptom and the only symptom that substantially differed between waves was fever, with 33% of SARS-CoV-2 infected children in the fourth wave vs. 13.6% in the third wave. Preschool children had the lowest prevalence of febrile illness compared to other age groups. CONCLUSION: Children and adolescents infected during the fourth wave of the pandemic in Israel, a Delta-dominant period, had a significantly higher rate of symptomatic febrile illness than the Alpha-dominant period. This phenomenon occurred across all age groups. WHAT IS KNOWN: • There are differences in COVID-19 severity among adults and children during different waves of the pandemic. • There is a paucity of data regarding symptomatic characteristics in children in large-scale cohorts aside from hospital settings. WHAT IS NEW: • In a time period dominated by the Delta variant, there were substantially more children with symptomatic disease and febrile illness compared to a period dominated by the alpha variant. • Preschool children had the lowest rate of febrile illness among all age groups.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Naturally Acquired Immunity versus Vaccine-induced Immunity, Reinfections versus Breakthrough Infections: A Retrospective Cohort Study.

BACKGROUND: Waning of protection against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) conferred by 2 doses of the BNT162b2 vaccine begins shortly after inoculation and becomes substantial within 4 months. With that, the impact of prior infection on incident SARS-CoV-2 reinfection is unclear. Therefore, we examined the long-term protection of naturally acquired immunity (protection conferred by previous infection) compared to vaccine-induced immunity. METHODS: A retrospective observational study of 124 500 persons, compared 2 groups: (1) SARS-CoV-2-naive individuals who received a 2-dose regimen of the BioNTech/Pfizer mRNA BNT162b2 vaccine, and (2) previously infected individuals who have not been vaccinated. Two multivariate logistic regression models were applied, evaluating four SARS-CoV-2-related outcomes-infection, symptomatic disease (coronavirus disease 2019 [COVID-19]), hospitalization, and death-between 1 June and 14 August 2021, when the Delta variant was dominant in Israel. RESULTS: SARS-CoV-2-naive vaccinees had a 13.06-fold (95% confidence interval [CI], 8.08-21.11) increased risk for breakthrough infection with the Delta variant compared to unvaccinated-previously-infected individuals, when the first event (infection or vaccination) occurred during January and February of 2021. The increased risk was significant for symptomatic disease as well. When allowing the infection to occur at any time between March 2020 and February 2021, evidence of waning naturally acquired immunity was demonstrated, although SARS-CoV-2 naive vaccinees still had a 5.96-fold (95% CI: 4.85-7.33) increased risk for breakthrough infection and a 7.13-fold (95% CI: 5.51-9.21) increased risk for symptomatic disease. CONCLUSIONS: Naturally acquired immunity confers stronger protection against infection and symptomatic disease caused by the Delta variant of SARS-CoV-2, compared to the BNT162b2 2-dose vaccine-indued immunity.

Association of BNT162b2 COVID-19 Vaccination During Pregnancy With Neonatal and Early Infant Outcomes.

Importance: Pregnant women were excluded from the BNT162b2 messenger RNA (mRNA) COVID-19 vaccine (Pfizer-BioNTech) preauthorization trial. Therefore, observational data on vaccine safety for prenatally exposed newborns are critical to inform recommendations on maternal immunization. Objective: To examine whether BNT162b2 mRNA vaccination during pregnancy is associated with adverse neonatal and early infant outcomes among the newborns. Design, Setting, and Participants: Population-based cohort study comprising all singleton live births in March through September 2021, within a large state-mandated health care organization in Israel, followed up until October 31, 2021. Exposure: Maternal BNT162b2 mRNA vaccination during pregnancy. Main Outcomes and Measures: Risk ratios (RR) of preterm birth, small birth weight for gestational age (SGA), congenital malformations, all-cause hospitalizations, and infant death. Stabilized inverse probability weighting was used to adjust for maternal age, timing of conception, parity, socioeconomic status, population subgroup, and maternal influenza immunization status. Results: The cohort included 24 288 eligible newborns (49% female, 96% born at ≥37 weeks' gestation), of whom 16 697 were exposed (n = 2134 and n = 9364 in the first and second trimesters, respectively) to maternal vaccination in utero. Median (IQR) follow-up after birth was 126 days (76-179) among exposed and 152 days (88-209) among unexposed newborns. No substantial differences were observed in preterm birth rates between exposed and unexposed newborns (RR = 0.95; 95% CI, 0.83-1.10) or SGA (RR = 0.97; 95% CI, 0.87-1.08). No significant differences were observed in the incidence of all-cause neonatal hospitalizations (RR = 0.99; 95% CI, 0.88-1.12), postneonatal hospitalizations after birth (RR = 0.95; 95% CI, 0.84-1.07), congenital anomalies (RR = 0.69; 95% CI, 0.44-1.04), or infant mortality over the study period (RR = 0.84; 95% CI, 0.43-1.72). Conclusions and Relevance: This large population-based study found no evident differences between newborns of women who received BNT162b2 mRNA vaccination during pregnancy, vs those of women who were not vaccinated, and contributes to current evidence in establishing the safety of prenatal vaccine exposure to the newborns. Interpretation of study findings is limited by the observational design.

SARS-CoV-2 RT-qPCR Test Detection Rates Are Associated with Patient Age, Sex, and Time since Diagnosis.

Quantifying the detection rate of the widely used quantitative RT-PCR (RT-qPCR) test for severe acute respiratory syndrome coronavirus 2 and its dependence on patient demographic characteristics and disease progression is key in designing epidemiologic strategies. Analyzing 843,917 test results of 521,696 patients, a "positive period" was defined for each patient between diagnosis of coronavirus disease 2019 and the last positive test result. The fraction of positive test results within this period was then used to estimate detection rate. Regression analyses were used to determine associations of detection with time of sampling after diagnosis, patient demographic characteristics, and viral RNA copy number based on RT-qPCR cycle threshold values of the next positive test result. The overall detection rate in tests performed within 14 days after diagnosis was 83.1%. This rate was higher at days 0 to 5 after diagnosis (89.3%). Furthermore, detection rate was strongly associated with age and sex. Finally, the detection rate with the Allplex 2019-nCoV RT-qPCR kit was associated, at the single-patient level, with viral RNA copy number (P < 10-9). These results show that the reliability of the test result is reduced in later days as well as for women and younger patients, in whom the viral loads are typically lower.

COVID-19 Vaccine Is Effective in Inflammatory Bowel Disease Patients and Is Not Associated With Disease Exacerbation.

BACKGROUND & AIMS: Studies have shown decreased response to coronavirus disease 2019 (COVID-19) vaccinations in some populations. In addition, it is possible that vaccine-triggered immune activation could trigger immune dysregulation and thus exacerbate inflammatory bowel diseases (IBD). In this population-based study we used the epi-Israeli IBD Research Nucleus validated cohort to explore the effectiveness of COVID-19 vaccination in IBD and to assess its effect on disease outcomes. METHODS: We included all IBD patients insured in 2 of the 4 Israeli health maintenance organizations, covering 35% of the population. Patients receiving 2 Pfizer-BioNTech BNT162b2 vaccine doses between December 2020 and June 2021 were individually matched to non-IBD controls. To assess IBD outcomes, we matched vaccinated to unvaccinated IBD patients, and response was analyzed per medical treatment. RESULTS: In total, 12,109 IBD patients received 2 vaccine doses, of whom 4946 were matched to non-IBD controls (mean age, 51 ± 16 years; median follow-up, 22 weeks; interquartile range, 4-24). Fifteen patients in each group (0.3%) developed COVID-19 after vaccination (odds ratio, 1; 95% confidence interval, 0.49-2.05; P = 1.0). Patients on tumor necrosis factor (TNF) inhibitors and/or corticosteroids did not have a higher incidence of infection. To explore IBD outcomes, 707 vaccinated IBD patients were compared with unvaccinated IBD patients by stringent matching (median follow-up, 14 weeks; interquartile range, 2.3-20.4). The risk of exacerbation was 29% in the vaccinated patients compared with 26% in unvaccinated patients (P = .3). CONCLUSIONS: COVID-19 vaccine effectiveness in IBD patients is comparable with that in non-IBD controls and is not influenced by treatment with TNF inhibitors or corticosteroids. The IBD exacerbation rate did not differ between vaccinated and unvaccinated patients.

Correlation of SARS-CoV-2-breakthrough infections to time-from-vaccine.

The short-term effectiveness of a two-dose regimen of the BioNTech/Pfizer mRNA BNT162b2 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine was widely demonstrated. However, long term effectiveness is still unknown. Leveraging the centralized computerized database of Maccabi Healthcare Services (MHS), we assessed the correlation between time-from-vaccine and incidence of breakthrough infection between June 1 and July 27, the date of analysis. After controlling for potential confounders as age and comorbidities, we found a significant 1.51 fold (95% CI, 1.38-1.66) increased risk for infection for early vaccinees compared to those vaccinated later that was similar across all ages groups. The increased risk reached 2.26- fold (95% CI, 1.80-3.01) when comparing those who were vaccinated in January to those vaccinated in April. This preliminary finding of vaccine waning as a factor of time from vaccince should prompt further investigations into long-term protection against different strains.

Evaluating red blood cell distribution width from community blood tests as a predictor of hospitalization and mortality in adults with SARS-CoV-2: a cohort study.

BACKGROUND: Red blood cell distribution width (RDW) has been assessed during COVID-19 patient hospitalization, however, further research should be done to evaluate RDW from routine community blood tests, before infection, as a risk factor for COVID-19 related hospitalization and mortality. PATIENTS AND METHODS: RDW was measured as a predictor along with age, sex, chronic illnesses, and BMI in logistic regressions to predict hospitalization and mortality. Hospitalization and mortality odds ratios (ORs) were estimated with 95% confidence intervals (CI). RDW was evaluated separately as continuous and discrete (High RDW ≥ 14.5) variables. RESULTS: Four thousand one hundred and sixty-eight patients were included in this study, where 824 patients (19.8%) had a high RDW value ≥14.5% (High RDW: 64.7% were female, mean age 58 years [±22] vs. Normal RDW: 60.2% female, mean age 46 years [±19]). Eight hundred and twenty-nine patients had a hospitalization, where the median time between positive PCR and hospital entry was 5 [IQR 1-18] days. Models were analyzed with RDW (continuous) and adjusted for age, sex, comorbidities, and BMI suggested an OR of 1.242 [95% CI = 1.187-2.688] for hospitalization and an OR of 2.911 [95% CI = 1.928-4.395] for mortality (p < .001). RDW (discrete) with the same adjustments presented an OR of 2.232 [95% CI = 1.853-1.300] for hospitalization and an OR of 1.263 [95% CI = 1.166-1.368] for mortality (p < .001). CONCLUSIONS: High RDW values obtained from community blood tests are associated with greater odds of hospitalization and mortality for patients with COVID-19.KEY MESSAGESRDW measures before SARS-CoV-2 infection is a predictive factor for hospitalization and mortality.RDW threshold of 14.5% provides high sensitivity and specificity for COVID-19 related mortality, comparatively to other blood tests.Patient records should be accessed by clinicians for prior RDW results, if available, followed by further monitoring.

Kinetics of SARS-CoV-2 anti-S IgG after BNT162b2 vaccination.

Deployment of the BNT162b2 mRNA Covid-19 Vaccine in Israel began in December 2020. This is a retrospective analysis of serological data, showing SARS-CoV-2 anti-S IgG kinetics in 116 Israeli health care workers receiving BNT162b2. Sero-conversion occurred in 14 days in all study participants, with IgG levels peaking approximately 30 days after initiation of the vaccination series. A statistically significant difference was observed in IgG levels between subjects younger than 50 years and older participants, although in all cases, IgG levels were well above the level considered reactive by the test's manufacturer. The importance of this difference needs to be studied further, but a potential difference in vaccine efficacy and vaccine effect length could possibly be present between these two groups.

Community-level evidence for SARS-CoV-2 vaccine protection of unvaccinated individuals.

Mass vaccination has the potential to curb the current COVID-19 pandemic by protecting individuals who have been vaccinated against the disease and possibly lowering the likelihood of transmission to individuals who have not been vaccinated. The high effectiveness of the widely administered BNT162b vaccine from Pfizer-BioNTech in preventing not only the disease but also infection with SARS-CoV-2 suggests a potential for a population-level effect, which is critical for disease eradication. However, this putative effect is difficult to observe, especially in light of highly fluctuating spatiotemporal epidemic dynamics. Here, by analyzing vaccination records and test results collected during the rapid vaccine rollout in a large population from 177 geographically defined communities, we find that the rates of vaccination in each community are associated with a substantial later decline in infections among a cohort of individuals aged under 16 years, who are unvaccinated. On average, for each 20 percentage points of individuals who are vaccinated in a given population, the positive test fraction for the unvaccinated population decreased approximately twofold. These results provide observational evidence that vaccination not only protects individuals who have been vaccinated but also provides cross-protection to unvaccinated individuals in the community.

Assessment of Effectiveness of 1 Dose of BNT162b2 Vaccine for SARS-CoV-2 Infection 13 to 24 Days After Immunization.

Importance: The BNT162b2 vaccine showed high efficacy against COVID-19 in a phase III randomized clinical trial. A vaccine effectiveness evaluation in a real-world setting is needed. Objective: To assess the short-term effectiveness of the first dose of the BNT162b2-vaccine against SARS-CoV-2 infection 13 to 24 days after immunization in a real-world setting. Design, Setting, and Participants: This comparative effectiveness study used data from a 2.6 million-member state-mandated health care system in Israel. Participants included all individuals aged 16 years and older who received 1 dose of the BNT162b2 vaccine between December 19, 2020, and January 15, 2021. Data were analyzed in March 2021. Exposure: Receipt of 1 dose of the BNT162b2 vaccine. Main Outcomes and Measures: Information was collected regarding medical history and positive SARS-CoV-2 polymerase chain reaction test and COVID-19 symptoms from 1 day after first vaccine to January 17, 2021. Daily and cumulative infection rates in days 13 to 24 were compared with days 1 to 12 after the first dose using Kaplan-Meier survival analysis and generalized linear models. Results: Data for 503 875 individuals (mean [SD] age, 59.7 [14.7] years; 263 228 [52.4%] women) were analyzed, of whom 351 897 had follow-up data for days 13 to 24. The cumulative incidence of SARS-CoV-2 infection was 2484 individuals (0.57%) during days 1 through 12 and 614 individuals (0.27%) in days 13 through 24. The weighted mean (SE) daily incidence of SARS-CoV-2 infection in days 1 through 12 was 43.41 (12.07) infections per 100 000 population and 21.08 (6.16) infections per 100 000 population in days 13 through 24, a relative risk reduction (RRR) of 51.4% (95% CI, 16.3%-71.8%). The decrease in incidence was evident from day 18 after the first dose. Similar RRRs were calculated in individuals aged 60 years or older (44.5%; 95% CI, 4.1%-67.9%), those younger than 60 years (50.2%; 95% CI, 14.1%-71.2%), women (50.0%; 95% CI, 13.5%-71.0%), and men (52.1%; 95% CI, 17.3%-72.2%). Findings were similar in subpopulations (eg, ultraorthodox Jewish: RRR, 53.5% [95% CI, 19.2%-73.2%]) and patients with various comorbidities (eg, cardiovascular diseases: RRR, 47.2% [95% CI, 7.8%-69.8%]). Vaccine effectiveness against symptomatic COVID-19 was 54.4% (95% CI, 21.4%-73.6%). Conclusions and Relevance: In this comparative effectiveness study of a single dose of the BNT162b2 vaccine, results were comparable to that of the phase III randomized clinical trial.

The Effectiveness of the Two-Dose BNT162b2 Vaccine: Analysis of Real-World Data.

BACKGROUND: Coronavirus disease 2019 (COVID-19) messenger RNA (mRNA) vaccines were shown to be highly efficacious in preventing the disease in randomized controlled trials; nonetheless, evidence on the real-world effectiveness of this vaccine is limited. Study objective was to evaluate the effectiveness of BNT162b2 vaccine in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19-related hospitalization and mortality. METHODS: This historical cohort study included members of a large health provider in Israel that were vaccinated with at least 1 dose of BNT162b2. The primary outcome was incidence rate of a SARS-CoV-2 infection confirmed with real-time polymerase chain reaction (rt-PCR), between 7 and 27 days after second dose (protection-period), as compared to days 1-7 after the first dose, where no protection by the vaccine is assumed (reference-period). RESULTS: Data of 1 178 597 individuals vaccinated with BNT162b2 were analyzed (mean age 47.7 years [SD = 18.1], 48.4% males) of whom 872 454 (74.0%) reached the protection period. Overall, 4514 infections occurred during the reference period compared to 728 during the protection period, yielding a weighted mean daily incidence of 54.8 per 100 000 (95% confidence interval [CI]: 26.1-115.0 per 100 000) and 5.4 per 100 000 (95% CI: 3.5-8.4 per 100 000), respectively. The vaccine effectiveness in preventing infection was 90% (95% CI: 79%-95%) and 94% (95% CI: 88%-97%) against COVID-19. Among immunosuppressed patients, vaccine effectiveness against infection was 71% (95% CI: 37%-87%). The adjusted hazard ratios for hospitalization in those infected were 0.82 (95% CI: .36-1.88), 0.45 (95% CI: .23-.90), and 0.56 (95% CI: .36-.89) in the age groups 16-44, 45-64. and ≥75 years, respectively. CONCLUSIONS: The effectiveness of the BNT162b2 vaccine is comparable to the one reported in the phase III clinical trial.

Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine.

Beyond their substantial protection of individual vaccinees, coronavirus disease 2019 (COVID-19) vaccines might reduce viral load in breakthrough infection and thereby further suppress onward transmission. In this analysis of a real-world dataset of positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results after inoculation with the BNT162b2 messenger RNA vaccine, we found that the viral load was substantially reduced for infections occurring 12-37 d after the first dose of vaccine. These reduced viral loads hint at a potentially lower infectiousness, further contributing to vaccine effect on virus spread.