Association between mRNA COVID-19 vaccine boosters and mortality in Japan: The VENUS study.

Although previous studies have shown no increased mortality risk after the primary series of COVID-19 mRNA vaccines, reports on booster doses are lacking. This study aimed to evaluate mortality risk after the mRNA vaccine boosters in addition to the primary series. This nested case-control study included two age-specific cohorts (18-64 and ≥65 years as of February 1, 2021) in two municipalities. All deaths were identified and matched five controls for each case at each date of death (index date) with risk set sampling according to municipality, age, and sex. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for mRNA vaccines (first to fifth doses) were estimated by comparing with no vaccination within 21 and 42 days before the index date using a conditional logistic regression model. The 18-64-years cohort comprised 431 cases (mean age, 57.0 years; men, 58.2%) and 2,155 controls (mean age, 56.0; men, 58.2%), whereas the ≥65-years cohort comprised 12,166 cases (84.0; 50.2%) and 60,830 controls (84.0, 50.2%). The aORs (95% CI) in 0-21 days after the third and fourth doses in the 18-64-years cohort were 0.62 (0.24, 1.62) and 0.38 (0.08, 1.84), respectively. The aORs (95% CI) after the third to fifth doses in the ≥65 years cohort were 0.36 (0.31, 0.43), 0.30 (0.25, 0.37), and 0.26 (0.20, 0.33), respectively. In conclusion, booster doses of mRNA vaccines do not increase mortality risk. These findings could help subsequent vaccine campaigns and alleviate vaccine hesitancy.

Increased risk of hypocalcemia with decreased kidney function in patients prescribed bisphosphonates based on real-world data from the MID-NET® in Japan: a new-user cohort study.

BACKGROUND: In the post-marketing stage, cases of hypocalcemia associated with bisphosphonate preparations (BPs) have been reported in patients with decreased kidney function, despite warning against use of BPs in such patients in the package insert (PI) of Japan. The purpose of this study was to investigate the safety of BPs in patients with decreased kidney function. METHODS: The cohort study was conducted in patients with osteoporosis and newly prescribed bisphosphonate utilizing real-world data from MID-NET® in Japan. The adjusted hazard ratios (aHRs) for hypocalcemia (a corrected serum Ca level < 8.00 mg/dL) relative to the normal group were calculated in each decreased kidney function group (mild, moderate or severe group). RESULTS: A total of 14,551 patients were included in the analysis, comprising 2,601 (17.88%) with normal (eGFR ≥ 90 mL/min/1.73m2), 7,613 (52.32%) with mild (60 ≤ eGFR < 90 mL/min/1.73m2), 3,919 (26.93%) with moderate (30 ≤ eGFR < 60 mL/min/1.73m2), and 418 (2.87%) with severe kidney function (eGFR < 30 mL/min/1.73m2). The aHRs (95% confidence interval) for hypocalcemia were 1.85 (0.75-4.57), 2.30 (0.86-6.21), and 22.74 (8.37-61.78) in the mild, moderate, and severe groups, respectively. The increased risk of hypocalcemia depending on kidney function was also observed even when calculating the aHR for each specific BP such as alendronate sodium hydrate, minodronic acid hydrate, and sodium risedronate hydrate. Furthermore, similar results were obtained in the sensitivity analysis by altering the outcome definition to a 20% or more reduction in corrected serum Ca level from the baseline, as well as when focusing on patients with more than one laboratory test result per 30 days during the follow-up period. CONCLUSIONS: These findings suggest that the risk of hypocalcemia during BP prescription is higher in patients with decreased kidney function, particularly those with severely decreased kidney function. The quantitative real-world evidence on the safety risk of BPs obtained in this study has led to the PI revision describing a relationship between hypocalcemia risk and decreased kidney function as a regulatory action in Japan and will contribute to promoting the proper use of BPs with appropriate risk management in clinical practice.

Development and validation of claims-based algorithms for identifying hospitalized patients with COVID-19 and their severity in 2020 and 2021.

BACKGROUND: This study aimed to develop and validate claims-based algorithms for identifying hospitalized patients with coronavirus disease (COVID-19) and the disease severity. METHODS: We used claims data including all patients at the National Center for Global and Medicine Hospital between January 1, 2020, and December 31, 2021. The claims-based algorithms for three statuses with COVID-19 (hospitalizations, moderate or higher status, and severe status) were developed using diagnosis codes (ICD-10 code: U07.1, B34.2) and relevant medical procedure code. True cases were determined using the COVID-19 inpatient registry and electronic health records. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each algorithm at 6-month intervals. RESULTS: Of the 75,711 total patients, number of true cases was 1,192 for hospitalizations, 622 for moderate or higher status, and 55 for severe status. The diagnosis code-only algorithm for hospitalization had sensitivities 90.4% to 94.9% and PPVs 9.3% to 19.4%. Among the algorithms consisting of both diagnosis codes and procedure codes, high sensitivity and PPV were observed during the following periods; 93.9% and 97.1% for hospitalization (January-June 2021), 90.4% and 87.5% for moderate or higher status (July-December 2021), and 92.3% and 85.7% for severe status (July-December 2020), respectively. Almost all algorithms had specificities and NPVs of approximately 99%. CONCLUSIONS: The diagnosis code-only algorithm for COVID-19 hospitalization showed low validity throughout the study period. The algorithms for hospitalizations, moderate or higher status, and severe status with COVID-19, consisting of both diagnosis codes and procedure codes, showed high validity in some periods.

Lower Risks of Gastrointestinal Perforation and Intestinal Obstruction in Patients with Atypical Antipsychotics in Comparison with Typical Antipsychotics Based on Real-World Data from the MID-NET® in Japan.

Intestinal perforation and obstruction are known to be one of the adverse events caused by antipsychotics; however, warning information on package inserts varies among antipsychotics. To investigate the risks of gastrointestinal perforation and intestinal obstruction in patients prescribed atypical antipsychotics compared with those in patients prescribed typical antipsychotics, a nested case-control study was conducted utilizing real-world data from the MID-NET® medical information database in Japan. The study period spanned from January 1, 2009, to December 31, 2018. We found that the risks of gastrointestinal perforation and intestinal obstruction in patients prescribed atypical antipsychotics were significantly lower than those in patients prescribed typical antipsychotics (adjusted odds ratio, 0.48; 95% confidence interval, 0.29-0.80). This finding was supported with prolonged periods for the exposure definition in the sensitivity analyses. In addition, no major differences in the risks of atypical antipsychotics, such as risperidone, quetiapine, olanzapine, and aripiprazole, were identified in this study. The safety profile regarding the lower risks of gastrointestinal perforation and intestinal obstruction in patients prescribed atypical antipsychotics should be considered when choosing antipsychotics in clinical practice in terms of the proper use of such drugs.

Bivalent Vaccine Effectiveness Among Adults Aged ≥65 Years During the BA.5-Predominant Period in Japan: The VENUS Study.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.5 became prevalent in July 2022 in Japan. Bivalent messenger RNA (mRNA) vaccines were approved as booster doses for individuals who received the primary series or booster dose by monovalent vaccines. We aimed to assess the effectiveness of bivalent vaccines in Japanese adults aged ≥65 years. Methods: We conducted a population-based cohort study using data collected from January 2019 to February 2023 in Japan. We included individuals aged ≥65 years in a municipality who received the first or second booster dose of monovalent mRNA vaccines. We estimated the effectiveness of the second or third booster dose of bivalent mRNA vaccines during the Omicron BA.5-predominant period (July-December 2022), compared with ≥90 days after the booster dose of monovalent vaccines. We used a Cox proportional hazard regression model with vaccination status as a time-dependent covariate. Results: A total of 81 977 individuals aged ≥65 years (mean [standard deviation] age, 78.3 [7.4] years; 33 487 male [40.8%]) were included in the study cohort. Among them, 57 396 were vaccinated with the second or third dose of bivalent vaccines (BA.1 or BA.4/5). The effectiveness against coronavirus disease 2019 (COVID-19) was estimated to be 57.9% (95% confidence interval, 52.7%-62.5%) for ≥14 days after the second or third bivalent booster dose, compared with 90 days after the first or second monovalent booster dose. Conclusions: The study showed that the bivalent mRNA vaccines as the second and third doses would provide protection against COVID-19 among adults ≥65 years in Japan.

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 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 (95% confidence interval) of BNT162b2 against infection, symptomatic infection, and hospitalization was 78.1% (65.2 to 87.8%), 79.1% (64.6 to 88.9%), and 93.5% (83.7 to 100%), respectively. CONCLUSIONS: BNT162b2 was highly effective against infection, symptomatic infection, and hospitalization in Japan's older adult population aged ≥65 years during the Delta-predominant period.

Multiregional Population-Based Cohort Study for Evaluation of the Association Between Herpes Zoster and mRNA Vaccinations for Severe Acute Respiratory Syndrome Coronavirus-2: The VENUS Study.

Background: This study was performed to assess the increased risk of herpes zoster (HZ) associated with mRNA vaccines for coronavirus disease 2019. Methods: This population-based cohort study was conducted in 4 municipalities in Japan. Individuals covered under public health insurance systems without a history of HZ were followed from October 1, 2020 to November 30, 2021. Incidence rates of HZ within 28 days of BNT162b2 or mRNA-1273 vaccination were compared. Adjusted incidence rate ratios (IRR) and 95% confidence intervals (CI) were estimated using a Poisson regression model, including vaccination status as a time-dependent covariate. Subgroup analyses by sex, age, and municipality were also conducted. Results: A total of 339 548 individuals (median age, 74 years) were identified. During follow up, 296 242 individuals (87.2%) completed the primary series, among whom 289 213 and 7019 individuals received homologous BNT162b2 and mRNA-1273 vaccines, respectively. The adjusted IRRs of the first and second BNT162b2 vaccinations were 1.05 (95% CI, 0.84-1.32) and 1.09 (95% CI, 0.90-1.32), respectively. No cases of HZ were observed after mRNA-1273 vaccination. In subgroup analysis, the adjusted IRR of the second BNT162b2 vaccination was 2.94 (95% CI, 1.41-6.13) in individuals aged <50 years old. Conclusions: No increased risk of HZ was found after BNT162b2 vaccination in the overall study population. However, an increased risk was observed in the younger subgroup.

Use of National Database of Health Insurance Claims and Specific Health Checkups for examining practical utilization and safety signal of a drug to support regulatory assessment on postmarketing drug safety in Japan.

The Pharmaceuticals and Medical Devices Agency (PMDA) has conducted many pharmacoepidemiological studies for postmarketing drug safety assessments based on real-world data from medical information databases. One of these databases is the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB), containing health insurance claims of almost all Japanese individuals (over 100 million) since April 2009. This article describes the PMDA's regulatory experiences in utilizing the NDB for postmarketing drug safety assessment, especially focusing on the recent cases of use of the NDB to examine the practical utilization and safety signal of a drug. The studies helped support regulatory decision-making for postmarketing drug safety, such as considering a revision of prescribing information of a drug, confirming the appropriateness of safety measures, and checking safety signals in real-world situations. Different characteristics between the NDB and the MID-NET® (another database in Japan) were also discussed for appropriate selection of data source for drug safety assessment. Accumulated experiences of pharmacoepidemiological studies based on real-world data for postmarketing drug safety assessment will contribute to evolving regulatory decision-making based on real-world data in Japan.

Characterizing Granulocytopenia Associated with Thiamazole in Patients with Hyperthyroidism Based on Real-World Data from the MID-NET in Japan.

Despite the requirement of routine blood tests during thiamazole treatment in Japan, granulocytopenia among patients treated with thiamazole has been occasionally reported to the Pharmaceuticals and Medical Devices Agency (PMDA). To characterize granulocytopenia in patients with thiamazole in Japan, the effects of routine blood tests were examined in a cohort of new users of thiamazole or propylthiouracil utilizing the MID-NET. The occurrence of granulocytopenia (neutrophil count ≤ 1,500/µL) in a given period was compared between patients with and without blood test results prior to the period. The trend in neutrophil count during thiamazole treatment was also compared between patients with and without granulocytopenia. A nested case-control study based on the cohort was conducted to identify potential risk factors for granulocytopenia during thiamazole treatment. In the new user cohort including 4,371 patients treated with thiamazole, the occurrence of granulocytopenia in patients who had undergone blood tests at all previous periods was similar or higher than that among those who had not undergone blood test in all previous periods (e.g., adjusted odds ratio in period 2 was 1.63). The neutrophil count was relatively lower in the group of patients with granulocytopenia even before the occurrence of granulocytopenia. In a nested case-control study, an upward tendency of the risk was observed when a patient was co-prescribed anti-arrhythmic drugs or antiulcer drugs with thiamazole. The characteristics of granulocytopenia during thiamazole treatment elucidated in this study should be recognized in clinical practice for the proper use of thiamazole.

The Longevity Improvement & Fair Evidence (LIFE) Study: Overview of the Study Design and Baseline Participant Profile.

BACKGROUND: The Longevity Improvement & Fair Evidence (LIFE) Study, which was launched in 2019, is a multi-region community-based database project that aims to generate evidence toward extending healthy life expectancy and reducing health disparities in Japan. Herein, we describe the LIFE Study's design and baseline participant profile. METHODS: Municipalities participating in the LIFE Study provide data from government-administered health insurance enrollees and public assistance recipients. These participants cover all disease types and age groups. Centered on healthcare claims data, the project also collects long-term care claims data, health checkup data, vaccination records, residence-related information, and income-related information. The different data types are converted into a common data model containing five modules (health care, long-term care, health checkup, socioeconomic status, and health services). We calculated the descriptive statistics of participants at baseline in 2018. RESULTS: The LIFE Study currently stores data from 1,420,437 residents of 18 municipalities. The health care module contains 1,280,756 participants (mean age: 65.2 years), the long-term care module contains 189,069 participants (mean age: 84.3 years), and the health checkup module contains 274,375 participants (mean age: 69.0 years). Although coverage and follow-up rates were lower among younger persons, the health care module includes 74,151 children (0-19 years), 273,157 working-age adults (20-59 years), and 933,448 older persons (≥60 years). CONCLUSION: The LIFE Study provides data from over 1 million participants and can facilitate a wide variety of life-course research and cohort studies. This project is expected to be a useful platform for generating real-world evidence from Japan.

Cardiovascular risk of urate-lowering drugs: A study using the National Database of Health Insurance Claims and Specific Health Checkups of Japan.

In the present study, we aimed to investigate the association between urate-lowering drugs and cardiovascular events, primarily focusing on the risk of febuxostat and topiroxostat when compared with allopurinol in Japan. We conducted an observational study with a cohort design using the National Database of Health Insurance Claims and Specific Health Checkups of Japan, including new urate-lowering drugs users between August 1, 2010, and March 31, 2018. Exposure and control groups were defined based on the first prescription of urate-lowering drugs as follows: febuxostat or topiroxostat for exposure groups, allopurinol for the control group, and benzbromarone for the secondary control group. The primary outcome was cardiovascular events, defined as a composite of acute coronary syndrome, cerebral infarction, and cerebral hemorrhage. Hazard ratios were estimated using a Cox proportional hazards model. The number of patients in each exposure and control group was 1,357,671 in the febuxostat group, 83,683 in the topiroxostat group, 1,273,211 in the allopurinol group, and 258,786 in the benzbromarone group. The adjusted hazard ratios for the cardiovascular risk were 0.97 (95% confidence interval [CI]: 0.95-0.98) for febuxostat and 0.84 (95% CI: 0.78-0.90) for topiroxostat groups. The benzbromarone group exhibited similar results. No increased cardiovascular risk was observed with febuxostat or topiroxostat when compared with allopurinol in patients with hyperuricemia in Japan. These results provide real-world evidence regarding the cardiovascular risk associated with urate-lowering drugs, indicating that no additional safety-related regulatory actions are warranted in Japan.

Descriptive Analysis for the Trend of Pharmacovigilance Planning in Risk Management Plans on New Drugs Approved During 2016-2019.

BACKGROUND: Japanese pharmaceutical authorities have conducted regulatory renovations of pharmacovigilance planning (PVP) since implementing new procedures for developing post-marketing study plans in 2018 in order to promote more focused and scientific approaches. This study aimed to descriptively assess the effects of those regulatory renovations on PVP for new drugs in Japan. METHODS: We identified PVP information (drug characteristics, efficacy and safety issues, and additional activities) from the first version of risk management plans for new drugs approved between 2016 and 2019. The following indicators were analyzed: (1) proportion of the number of drugs with at least one efficacy issue among all the drugs, (2) proportion of the number of safety issues with additional activity among all the safety issues, and (3) proportion of database studies among all additional activities. RESULTS: In total, 168 drugs, 1212 safety issues, and 301 additional activities were identified. The proportion of drugs with at least one efficacy issue decreased from 91.4% in 2016 to 27.3% in 2019, and the proportion of safety issues with additional activity also decreased from 93.9% in 2016 to 53.7% in 2019. In contrast, the proportion of database studies increased from 0 to 19.2%. The percentages of additional activities targeting important identified and potential risks also gradually decreased during the 4-year period. CONCLUSION: Notable changes in the three indicators during 2016-2019 were observed, which suggests that regulatory renovation has affected PVP in Japan.

Prescription trend and lactic acidosis in patients prescribed metformin before and after the revision of package insert for allowing metformin administration to patients with moderately decreased kidney function based on real-world data from MID-NET® in Japan.

Introduction: This study was conducted to understand the impact of package insert (PI) revision in Japan on 18 June 2019 to allow metformin use for patients with moderately decreased kidney function (30 ≤ estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2). Methods: A new user cohort design was employed to examine the prescription trend and the occurrence of lactic acidosis in patients prescribed metformin before and after PI revision using the Medical Information Database Network (MID-NET®). Results: From 12 May 2016 to 31 March 2020, 5,874 patients (before, n = 4,702; after, n = 1,172) were identified as new metformin users, including 1,145 patients (before, n = 914; after, n = 231) with moderately decreased kidney function. Although no marked changes in metformin prescription were observed before and after PI revision, the daily metformin dose at the first prescription decreased after PI revision. For both before and after PI revision, less than 10 cases of lactic acidosis occurred in all patients prescribed metformin, and no lactic acidosis was observed in patients with moderately decreased kidney function. Conclusion: The results of this study are useful for understanding the safety of metformin use in patients with decreased kidney function and suggest no worse impacts of PI revision in Japan, indicating no further safety concerns on metformin use in patients with moderately decreased kidney function under the situation with careful use and safety monitoring of metformin.

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.

Development and application of a Japanese vaccine database for comparative assessments in the post-authorization phase: The Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study.

BACKGROUND: Japan currently lacks a data platform that can support quantitative assessments of the causal relationships between vaccines and adverse events. This study describes the development and application of the Vaccine Effectiveness, Networking, and Universal Safety (VENUS) Study to facilitate such assessments. METHODS: A database was created by linking public insurance enrollees' claims data with vaccination records acquired from participating municipalities. To provide an overview of the study data, we produced descriptive statistics of sex, age, and vaccinations. We also conducted a pilot study using the database to assess influenza vaccine safety during the 2018/2019 season among older persons (≥65 years) residing in a single municipality. RESULTS: Our database was created using data from approximately 1.12 million individuals in 7 municipalities between 2013 and 2020. The data during fiscal year 2018 included 853,016 individuals (male: 363,079, female: 489,937) with a median age of 70 years (interquartile range: 52-79). We obtained information on 17 vaccine types, including the pneumococcal vaccine and influenza vaccine. In the pilot study, we analyzed 48,723 vaccinated persons matched with 48,723 unvaccinated persons. The only adverse event that occurred in both groups was Bell's palsy, which had an adjusted incidence rate ratio of 1.21 (95 % confidence interval: 0.48-3.07). CONCLUSIONS: The VENUS Study is Japan's first healthcare data platform that enables comparative assessments of vaccinated and unvaccinated persons in large samples covering all age groups. Efforts are underway to increase the number of participating municipalities and to generate evidence on vaccine effectiveness and safety.

Acute and delayed psychiatric sequelae among patients hospitalised with COVID-19: a cohort study using LIFE study data.

Background: Characterising the psychiatric sequelae of coronavirus disease 2019 (COVID-19) can inform the development of long-term treatment strategies. However, few studies have examined these sequelae at different time points after COVID-19 infection. Aims: The study aimed to investigate the incidences and risks of acute and delayed psychiatric sequelae in patients hospitalised with COVID-19 in Japan. Methods: This retrospective cohort study was conducted using a database comprising healthcare claims data from public health insurance enrollees residing in a Japanese city. We analysed a primary cohort comprising patients hospitalised with COVID-19 between March 2020 and July 2021 and two control cohorts comprising patients hospitalised with influenza or other respiratory tract infections (RTI) during the same period. We calculated the incidences of acute (1-3 months after infection) and delayed (4-6 months after infection) psychiatric sequelae. These sequelae were identified using diagnosis codes and categorised as mood/anxiety/psychotic disorder, mood disorder, anxiety disorder, psychotic disorder or insomnia. Multivariable logistic regression models were used to estimate the odds ratios (ORs) of psychiatric sequelae occurrence after COVID-19 infection compared with influenza and other RTI. Results: The study population with acute psychiatric sequela consisted of 662 patients with COVID-19, 644 patients with influenza, and 7369 patients with RTI who could be followed for 3 months; the study population with delayed psychiatric sequelae consisted of 371 patients with COVID-19, 546 patients with influenza, and 5397 patients with RTI who could be followed for 6 months. In the analysis of acute psychiatric sequelae, COVID-19 had significantly higher odds of mood/anxiety/psychotic disorder (OR: 1.39, p=0.026), psychotic disorder (OR: 2.13, p<0.001), and insomnia (OR: 2.59, p<0.001) than influenza, and significantly higher odds of insomnia (OR: 1.44, p=0.002) and significantly lower odds of anxiety disorder (OR: 0.56, p<0.001) than other RTI. In the analysis of delayed psychiatric sequelae, COVID-19 had significantly higher odds of psychotic disorder (OR: 2.25, p=0.007) than influenza, but significantly lower odds of anxiety disorder (OR: 0.55, p=0.011) than other RTI. Conclusions: COVID-19 was generally associated with an increased risk of psychiatric sequelae occurring within 3 months after infection, but had a lower risk of new psychiatric sequelae developing 4-6 months after infection.

Influenza vaccine effectiveness against hospitalization during the 2018/2019 season among older persons aged ≥ 75 years in Japan: The LIFE-VENUS Study.

BACKGROUND: Older persons are recommended to receive annual influenza vaccinations due to their increased susceptibility to influenza infections and related complications. Routine assessments of influenza vaccine effectiveness (IVE) in older persons may help to improve vaccine development and vaccination strategies, but there is a lack of consistent epidemiological data from Japan. This study aimed to evaluate IVE against hospitalization during the 2018/2019 season among older persons aged ≥ 75 years in Japan. METHODS: This cohort study was conducted using insurance claims data and vaccination records provided by the Longevity Improvement & Fair Evidence - Vaccine Effectiveness, Networking, and Universal Safety (LIFE-VENUS) Study. The study cohort comprised older persons aged ≥ 75 years residing in an urban municipality in Japan. Vaccinated participants were identified through vaccination records from October 2018 to January 2019, and were matched with unvaccinated participants using a 1:1 ratio. The IVE against hospitalization was calculated as (1-hazard ratio) × 100% while adjusting for covariates such as age, sex, comorbidities, previous vaccinations, and care needs levels. RESULTS: We analyzed 30,881 vaccinated participants matched with 30,881 unvaccinated participants. Among these, 587 (1.9%) vaccinated participants and 644 (2.1%) unvaccinated participants were hospitalized during the 2018/2019 season. The adjusted IVE against hospitalization was estimated to be 28.9% (16.6-39.4%). CONCLUSIONS: The influenza vaccine for the 2018/2019 season showed moderate effectiveness among older persons in Japan. The LIFE-VENUS Study represents a potential platform for the continued monitoring of IVE among the older Japanese population.