Real-World Effectiveness of the mRNA COVID-19 Vaccines in Japan: A Case–Control Study

Effectiveness of BNT162b2 Against Infection, Symptomatic Infection, and Hospitalization Among Older Adults Aged ≥65 Years During the Delta Variant Predominance in Japan: The VENUS Study

BACKGROUND

We evaluated the effectiveness of the BNT162b2 vaccine against infection, symptomatic infection, and hospitalization in older people during the Delta-predominant period (July 1 to September 30, 2021).

METHODS

We performed a population-based cohort study in an older adult population aged ≥65 years using data from the Vaccine Effectiveness, Networking, and Universal Safety Study conducted from January 1, 2019, to September 30, 2021, in Japan. We matched BNT162b2-vaccinated and -unvaccinated individuals in a 1:1 ratio on the date of vaccination of the vaccinated individual. We evaluated the effectiveness of the vaccine against infection, symptomatic infection, and coronavirus disease (COVID-19)-related hospitalization by comparing the vaccinated and unvaccinated groups. We estimated the risk ratio and risk difference using the Kaplan-Meier method with inverse probability weighting. The vaccine effectiveness was calculated as (1 - risk ratio) × 100%.

RESULTS

The study included 203,574 matched pairs aged ≥65 years. At 7 days after the second dose, the vaccine effectiveness of BNT162b2 against infection, symptomatic infection, and hospitalization was 78.1% (95% confidence interval [CI], 65.2-87.8%), 79.1% (95% CI, 64.6-88.9%), and 93.5% (95% CI, 83.7-100%), respectively.

CONCLUSION

BNT162b2 was highly effective against infection, symptomatic infection, and hospitalization in Japan's older adult population aged ≥65 years during the Delta-predominant period.

Associated organs and system with COVID-19 death with information of organ support: a multicenter observational study

BACKGROUND

The organ dysfunction that is associated with death in COVID-19 patients has not been determined in multicenter epidemiologic studies. In this study, we evaluated the major association with death, concomitant organ dysfunction, and proportion of multiple organ failure in deaths in patients with COVID-19, along with information on organ support.

METHODS

We performed an observational cohort study using the Japanese multicenter research of COVID-19 by assembling a real-world data (J-RECOVER) study database. This database consists of data on patients discharged between January 1 and September 31, 2020, with positive SARS-CoV-2 test results, regardless of intensive care unit admission status. These data were collected from the Diagnosis Procedure Combination and electronic medical records of 66 hospitals in Japan. The clinician identified and recorded the organ responsible for the death of COVID-19.

RESULTS

During the research period, 4,700 patients with COVID-19 were discharged from 66 hospitals participating in the J-RECOVER study; of which, 272 patients (5.8%) from 47 institutions who died were included in this study. Respiratory system dysfunction (87.1%) was the leading association with death, followed by cardiovascular (4.8%), central nervous (2.9%), gastrointestinal (2.6%), and renal (1.1%) dysfunction. Most patients (96.7%) who died of COVID-19 had respiratory system damage, and about half (48.9%) had multi-organ damage. Of the patients whose main association with death was respiratory dysfunction, 120 (50.6%) received mechanical ventilation.

CONCLUSION

This study showed that although respiratory dysfunction was the most common association with death in many cases, multi-organ dysfunction was associated with death due to COVID-19.

Comparison of self-reported symptoms in COVID-19 patients who had or had not previously received COVID-19 mRNA vaccination

Although mRNA coronavirus disease 2019 (COVID-19) vaccines have been reported for high effectiveness against symptoms, it remains unclear whether post-vaccination infections are less symptomatic than infections in vaccine-naive individuals. We included patients with COVID-19 diagnosed by polymerase chain reaction tests during Japan's alpha and delta variant epidemics. COVID-19 symptoms at approximately 4 weeks were compared based on COVID-19 vaccination status. In total, 398 cases (372 symptomatic and 26 asymptomatic; 286 unvaccinated, 66 vaccinated with one dose, and 46 with two doses) were analyzed. The most common symptoms were fever (78.4%), fatigue (78.4%), cough (74.4%), loss of taste or smell (62.8%), and headache (59.8%). Post-vaccination infections were significantly less likely to be symptomatic. Possible confounder-adjusted odds ratios of two vaccine doses against fatigue, dry eyes and mouth, insomnia, fever, shortness of breath, unusual muscle pains, and loss of taste or smell were 0.18 (95% confidence interval [CI]: 0.09-0.38), 0.22 (95% CI: 0.08-0.59), 0.33 (95% CI: 0.14-0.80), 0.31 (95% CI: 0.15-0.63), 0.36 (95% CI: 0.16-0.76), 0.40 (95% CI: 0.19-0.82), and 0.44 (95% CI: 0.22-0.87), respectively. Post-vaccination infections after two mRNA COVID-19 vaccine doses show milder and fewer symptoms than infections in unvaccinated patients, highlighting the effectiveness of vaccination.

Real-World Effectiveness of Four Types of COVID-19 Vaccines

BACKGROUND

There is a scarcity of evidence regarding the real-world effectiveness of coronavirus disease 2019 (COVID-19) vaccines. This was the first study to evaluate the effectiveness of four types of vaccines against asymptomatic and symptomatic infection, and COVID-19 outcomes among the general population.

METHODS

This was a matched comparison group quasi-experimental study conducted in Jordan between 1 January and 29 August 2021. In the first part of the study, 1200 fully vaccinated individuals were matched with 1200 unvaccinated control participants. In order to measure vaccine effectiveness, the infection rates of both vaccinated and unvaccinated groups were calculated. The second part of the study included measuring specific anti-SARS CoV-2 immune cells and antibodies.

RESULTS

BNT162b2 (Pfizer, New York, NY, USA) showed a significantly higher effectiveness against asymptomatic COVID-19 infection (91.7%) and hospitalization (99.5%) than BBIBP-CorV (Sinopharm, Beijing, China) (88.4% and 98.7%, respectively) and ChAdOx1 nCoV-19 (AstraZeneca, Cambridge, UK) (84.3%, and 98.9%, respectively). The effectiveness rates of the Sputnik V (Gamaleya Research Institute, Moscow, Russia) vaccine against asymptomatic, symptomatic, and hospitalization were 100%, 100%, and 66.7%, respectively. The highest median anti-spike (S) IgG values were seen in individuals who received BNT162b2 (2.9 AU/mL) and ChAdOx1 nCoV-19 (2.8 AU/mL) vaccines. The levels of anti-S IgG were significantly decreased after 7 months of vaccination with BNT162b2 and BBIBP-CorV. There were significant decreases in the median number of neutralizing antibodies one month and seven months after receiving BNT162b2 (from 88.5 to 75.2 4 Bioequivalent Allergen Unit per milliliter/mL), BBIBP-CorV (from 69.5 to 51.5 BAU/mL), and ChAdOx1 nCoV-19 (from 69.2 to 58.BAU/mL) vaccines. The highest percentage of T cells specific to COVID-19 vaccine was found in individuals who received BNT162b2 (88.5%).

CONCLUSION

All four vaccines evaluated in this study showed effectiveness against asymptomatic COVID-19 infection, symptomatic infection, hospitalization, and death. Furthermore, BNT162b2, BBIBP-CorV, and ChAdOx1 nCoV-19 induced high levels of immunology markers within one month of vaccination.

Real-world vaccine effectiveness of mRNA vaccines for SARS-CoV-2; a test-negative case-control study in a medium-sized clinic

Although nationwide immunization with SARS-CoV-2 mRNA vaccines began in February 2021, the evaluation of vaccine effectiveness (VE) using a test-negative design has not been conducted adequately in Japan. To evaluate the effectiveness of the SARS-CoV-2 mRNA vaccines, we conducted a test-negative case-control study during the periods dominated by the Delta and Omicron variants. In total, 518 and 358 adult participants with COVID-19-like symptoms were tested for the virus from August to October 2021 (Delta variant predominance) and in February 2022 (Omicron variant surge), at the Kawasaki Saiwai Clinic. During Delta variant predominance, the effectiveness of full vaccination was 90.4% (95% confidence interval [CI]: 82.1-94.8) and 97.3% (95% CI: 71.7-99.7) against all COVID-19 and moderate-to-severe disease, respectively. However, partial vaccination failed to show effectiveness against moderate-to-severe COVID-19. The effectiveness of the mRNA vaccines against all COVID-19 infection declined to 16.1% (95% CI: -81.0 to 61.1) in February 2022. Our results indicated that, although mRNA vaccines showed significant preventive effects against all COVID-19 during Delta variant predominance, these preventive effects waned during Omicron variant surge. To the best of our knowledge, this is the first study that evaluated VE in the Japanese population during both periods.

Effectiveness of messenger RNA vaccines against infection with SARS-CoV-2 during the periods of Delta and Omicron variant predominance in Japan: the Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study

OBJECTIVES

We aimed to evaluate COVID-19 messenger RNA vaccine effectiveness during the Delta- and Omicron-predominant periods in Japan.

METHODS

We conducted a population-based cohort study among individuals aged 16-64 years during two periods: the Delta-predominant period (July 1-December 31, 2021) and the Omicron-predominant period (January 1-March 29, 2022).

RESULTS

When comparing individuals who were vaccinated with those who were unvaccinated, the effectiveness of a second dose against symptomatic infection was 89.8% (95% confidence interval [CI]: 80.5-94.7%) during the Delta-predominant period and 21.2% (95% CI: 11.0-30.3%) during the Omicron-predominant period. The effectiveness of a third dose against symptomatic infection was 71.8% (95% CI: 60.1-80.1%) during the Omicron-predominant period.

CONCLUSION

Vaccine effectiveness against symptomatic infection decreased during the Omicron-predominant period but was maintained by a third dose.

Effectiveness of a Third Dose of COVID-19 mRNA Vaccine During the Omicron BA.1- and BA.2-Predominant Periods in Japan: The VENUS Study

Background

Vaccine effectiveness against the severe acute respiratory syndrome coronavirus 2 Omicron BA.2 sublineage in Japan is unknown. We assessed the effectiveness of a third dose of COVID-19 mRNA vaccine compared with that of 2 doses.

Methods

We performed a population-based cohort study using a municipality database located in the Chubu region of Japan during the Omicron BA.1- and BA.2-predominant periods (January 1-March 31, 2022 and April 1-27, 2022, respectively). We included residents aged ≥16 years who received a second vaccine dose at ≥14 days before the start of each period, regardless of the third dose. We compared the data at 14 days after the second and third dose and at 2-week intervals from 14 days to 10 weeks after the third dose using a Cox regression model. Vaccine effectiveness was defined as (1 - hazard ratio) × 100 (%).

Results

In total, 295 705 and 288 184 individuals were included in the BA.1- and BA.2-predominant periods, respectively. The effectiveness of a third dose against infection was 62.4% and 48.1% in the BA.1- and BA.2-predominant periods, respectively. Vaccine effectiveness at 2-3 weeks and ≥10 weeks after the third dose decreased from 63.6% (95% confidence interval [CI], 56.4-69.5%) to 52.9% (95% CI, 41.1-62.3%) and from 54.5% (95% CI, 3.0-78.7%) to 40.1% (95% CI, 15.1-57.7%) in the BA.1- and BA.2-predominant periods, respectively.

Conclusions

A third dose was moderately effective against BA.1 and BA.2 sublineages, but its effectiveness decreased by approximately 10% age points from 2-3 weeks to ≥10 weeks after the third vaccination.