Enhancing Protection for Vulnerable Populations with Bivalent COVID-19 Vaccines


Insights from the Annual Conference on Vaccinology Research (ACVR) in mitigating severe outcomes in older adults and individuals with underlying medical conditions.

mrna covid vaccine

Mrna vaccination.

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This study aimed to evaluate the relative vaccine effectiveness (rVE) of 2 mRNA bivalent vaccines, mRNA-1273.222 (Moderna, Inc) and BNT162b2 bivalent (Pfizer-BioNTech), in US adults with underlying medical conditions linked to severe COVID-19. mRNA-1273.222 showed higher effectiveness than BNT162b2 in preventing COVID-19-related hospitalizations among individuals at increased risk for severe outcomes.

Among a cohort of 1,961,014 individuals, 758,803 were administered mRNA-1273.222, while 1,202,211 received BNT162b2. After applying weighting, baseline characteristics were comparable. The average age was 61 years, with prevalent underlying conditions including obesity and diabetes. mRNA-1273.222 exhibited an rVE of 10.9% (95% CI: 6.2%–15.2%) against COVID-19-related hospitalizations and 3.2% (95% CI: 1.7%–4.7%) against outpatient visits, in contrast to BNT162b2. Subgroup analysis revealed higher rVEs for mRNA-1273.222 among patients with diabetes, immunocompromised status, cardiovascular disease, lung disease, and chronic kidney disease.

This retrospective cohort study utilized electronic health record data from Veradigm in the US, identifying adults aged 18 years and older with at least one underlying medical condition associated with severe COVID-19. Participants were administered either mRNA-1273.222 or BNT162b2 between August 31, 2022, and February 28, 2023. Follow-up commenced 7 days post-vaccination and concluded at the earliest occurrence of relevant events. Inverse probability of treatment weighting was applied to adjust for baseline differences. The primary outcome assessed was COVID-19-related hospitalizations, with outpatient visits serving as a secondary measure. Adjusted hazard ratios and rVEs were estimated through multivariate Cox regression analysis.

The present analysis has limitations, comparisons were made among non-randomized groups, which could introduce biases into the findings. The study only encompassed individuals who had utilized healthcare services within the preceding 365 days before the index date. This selection criterion might affect the generalizability of the results to the broader population. Additionally, individuals vaccinated towards the end of the vaccination intake period might have had a shorter follow-up duration, potentially impacting the accuracy of the outcomes. Finally, variations in healthcare data were noted, which could influence the interpretation and reliability of the study findings.

In conclusion, it is important to consider the limitations highlighted in this analysis when interpreting the results. Continuous evaluation of vaccine effectiveness remains imperative, particularly given the evolving landscape of SARS-CoV-2 variants. This ongoing assessment is vital for protection, especially for vulnerable populations who are at higher risk of more severe outcomes from COVID-19.

Kopel H, Nguyen V, Bogdanov, et. al. Comparative Effectiveness of the Bivalent COVID-19 mRNA Vaccines, mRNA1273-222 and BNT162b2, in Adults at High Risk for Severe COVID-19 in the US. Oral Abstract #20 presented at NFID 2024 Annual Conference on Vaccine Research. May 8-10. Online.
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