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This retrospective cohort study evaluated the comparative vaccine effectiveness (cVE) of licensed standard‐dose cell‐based versus egg‐based influenza vaccines in preventing influenza hospitalization among adults 18–64 years during the 2022–2023 season. The cohort included eligible Kaiser Permanente Southern California members who received ≥ 1 dose of influenza vaccine (n = 848,334). The adjusted cVE against influenza hospitalization was −10.1% (95% CI: −49.8%, 37.8%) in the 18‐ to 49‐year‐old cohort. In the 50‐ to 64‐year‐old cohort, the adjusted cVE was 14.9% (−33.8%, 52.1%). Cell‐based and egg‐based influenza vaccines conferred comparable protection against influenza hospitalization in adults 18–64 years of age in the 2022–2023 season. [ABSTRACT FROM AUTHOR]

Background Influenza causes substantial morbidity, particularly among older individuals. Updated data on the effectiveness of currently licensed vaccines in this population are needed. Methods At Kaiser Permanente Southern California, we conducted a retrospective cohort study to evaluate comparative vaccine effectiveness (cVE) of high-dose (HD), adjuvanted, and standard-dose (SD) cell-based influenza vaccines, relative to the SD egg-based vaccine. We included adults aged ≥65 years who received an influenza vaccine between 1 August 2022 and 31 December 2022, with follow-up up to 20 May 2023. Primary outcomes were: (1) influenza-related medical encounters and (2) polymerase chain reaction (PCR)-confirmed influenza-related hospitalization. Adjusted hazard ratios (aHR) were estimated by Cox proportional hazards regression, adjusting for confounders using inverse probability of treatment weighting (IPTW). cVE (%) was calculated as (1—aHR) × 100 when aHR ≤1, and ([1/aHR]—1) × 100 when aHR >1. Results Our study population (n = 495 119) was 54.9% female, 46.3% non-Hispanic White, with a median age of 73 years (interquartile range [IQR] 69–79). Characteristics of all groups were well balanced after IPTW. Adjusted cVEs against influenza-related medical encounters in the HD, adjuvanted, and SD cell-based vaccine groups were 9.1% (95% confidence interval [CI]:.9, 16.7), 16.9% (95% CI: 1.7, 29.8), and −6.3 (95% CI: −18.3, 6.9), respectively. Adjusted cVEs against PCR-confirmed hospitalization in the HD, adjuvanted, and SD cell-based groups were 25.1% (95% CI:.2, 43.8), 61.6% (95% CI: 18.1, 82.0), and 26.4% (95% CI: −18.3, 55.7), respectively. Conclusions Compared to the SD egg-based vaccine, HD and adjuvanted vaccines conferred additional protection against influenza-related outcomes in the 2022–2023 season in adults ≥65 years. Our results provide real-world evidence of the comparative effectiveness of currently licensed vaccines. [ABSTRACT FROM AUTHOR]

The response letter addresses concerns raised about a study comparing the effectiveness of a third dose of mRNA-1273 versus BNT162b2 COVID-19 vaccines among immunocompromised US adults. The study used observational data due to ethical concerns about conducting placebo-controlled trials in this population. Rigorous statistical methods and sensitivity analyses were employed to address limitations and ensure the reliability of the results. The study's findings align with other real-world studies comparing the two vaccines in different populations. The letter was authored by Mihaela Georgieva, Tianyu Sun, and Ekkehard Beck, who are employees of Moderna, Inc., and funded by the same company. [Extracted from the article]

To compare the real-world effectiveness of a third dose of mRNA-1273 versus a third dose of BNT162b2 against breakthrough COVID-19 hospitalizations among adults aged ≥ 65 years who completed a primary series of an mRNA-based COVID-19 vaccine (regardless of which primary series was received). This observational comparative vaccine effectiveness (VE) study was conducted using administrative claims data from the US HealthVerity database (September 22, 2021, to August 31, 2022). A third dose of mRNA-1273 versus BNT162b2 was assessed for preventing COVID-19 hospitalizations and medically attended COVID-19 among adults aged ≥ 65 years. Inverse probability of treatment weighting was applied to balance baseline characteristics between vaccine groups. Incidence rates from patient-level data and hazard ratios (HRs) with 95 % confidence intervals (CIs) using weighted Cox proportional hazards models were calculated to estimate relative VE for each outcome. Overall, 94,587 and 92,377 individuals received a third dose of mRNA-1273 and BNT162b2, respectively. Among the weighted population, the median age was 69 years (interquartile range, 66–74), 53 % were female, and 46 % were commercially insured. COVID-19 hospitalization rates per 1000 person-years (PYs) were 5.61 (95 % CI, 5.13–6.09) for mRNA-1273 and 7.06 (95 % CI, 6.54–7.57) for BNT162b2 (HR, 0.82; 0.69–0.98). Medically attended COVID-19 rates per 1000 PYs (95 % CI) were 95.05 (95 % CI, 93.03–97.06) for mRNA-1273 and 106.55 (95 % CI, 104.53–108.57) for BNT162b2 (HR, 0.93; 0.89–0.98). Results from this observational comparative VE database study provide evidence that among older adults, a third dose of mRNA-1273 was more effective in preventing breakthrough COVID-19 hospitalization and medically attended COVID-19 infection compared with a third dose of BNT162b2. [ABSTRACT FROM AUTHOR]