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Comparative Risks of Potential Adverse Events Following COVID-19 mRNA Vaccination Among Older Adults in the US
TAKE-HOME MESSAGE
- In this retrospective cohort study, the authors sought to compare the risk of adverse events following COVID-19 mRNA vaccination with the mRNA-1273 vaccine versus the BNT162b2 vaccine in older adults in the US. The receipt of the mRNA-1273 vaccine was associated with a lower risk of pulmonary embolism, thromboembolic events, and diagnosed COVID-19 infection compared with that of the BNT162b2 vaccine. When stratified by frailty, these differences were more pronounced among participants in the non-frail group.
- This study adds to our current understanding of adverse events following these two mRNA vaccinations in a population of older adults further stratified by frailty level. The authors postulate that some of these differences can be explained by the increased efficacy of the mRNA-1273 vaccine in preventing COVID-19 infection in this population.
abstract
This abstract is available on the publisher's site.
Access this abstract nowIMPORTANCE
Head-to-head safety comparisons of the mRNA vaccines for SARS-CoV-2 are needed for decision making; however, current evidence generalizes poorly to older adults, lacks sufficient adjustment, and inadequately captures events shortly after vaccination. Additionally, no studies to date have explored potential variation in comparative vaccine safety across subgroups with frailty or an increased risk of adverse events, information that would be useful for tailoring clinical decisions.
OBJECTIVE
To compare the risk of adverse events between mRNA vaccines for COVID-19 (mRNA-1273 and BNT162b2) overall, by frailty level, and by prior history of the adverse events of interest.
DESIGN, SETTING, AND PARTICIPANTS
This retrospective cohort study was conducted between December 11, 2020, and July 11, 2021, with 28 days of follow-up following the week of vaccination. A novel linked database of community pharmacy and Medicare claims data was used, representing more than 50% of the US Medicare population. Community-dwelling, fee-for-service beneficiaries aged 66 years or older who received mRNA-1273 vs BNT162b2 as their first COVID-19 vaccine were identified. Data analysis began on October 18, 2022.
EXPOSURE
Dose 1 of mRNA-1273 vs BNT162b2 vaccine.
MAIN OUTCOMES AND MEASURES
Twelve potential adverse events (eg, pulmonary embolism, thrombocytopenia purpura, and myocarditis) were assessed individually. Frailty was measured using a claims-based frailty index, with beneficiaries being categorized as nonfrail, prefrail, and frail. The risk of diagnosed COVID-19 was assessed as a secondary outcome. Generalized linear models estimated covariate-adjusted risk ratios (RRs) and risk differences (RDs) with 95% CIs.
RESULTS
This study included 6 388 196 eligible individuals who received the mRNA-1273 or BNT162b2 vaccine. Their mean (SD) age was 76.3 (7.5) years, 59.4% were women, and 86.5% were White. A total of 38.1% of individuals were categorized as prefrail and 6.0% as frail. The risk of all outcomes was low in both vaccine groups. In adjusted models, the mRNA-1273 vaccine was associated with a lower risk of pulmonary embolism (RR, 0.96 [95% CI, 0.93-1.00]; RD, 9 [95% CI, 1-16] events per 100 000 persons) and other adverse events in subgroup analyses (eg, 11.0% lower risk of thrombocytopenia purpura among individuals categorized as nonfrail). The mRNA-1273 vaccine was also associated with a lower risk of diagnosed COVID-19 (RR, 0.86 [95% CI, 0.83-0.87]), a benefit that was attenuated by frailty level (frail: RR, 0.94 [95% CI, 0.89-0.99]).
CONCLUSIONS AND RELEVANCE
In this cohort study of older US adults, the mRNA-1273 vaccine was associated with a slightly lower risk of several adverse events compared with BNT162b2, possibly due to greater protection against COVID-19. Future research should seek to formally disentangle differences in vaccine safety and effectiveness and consider the role of frailty in assessments of COVID-19 vaccine performance.
Additional Info
Comparative Risks of Potential Adverse Events Following COVID-19 mRNA Vaccination Among Older US Adults
JAMA Netw Open 2023 Aug 01;6(8)e2326852, DA Harris, KN Hayes, AR Zullo, V Mor, P Chachlani, Y Deng, EP McCarthy, DA Djibo, CN McMahill-Walraven, S GravensteinFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
This retrospective cohort study of over 6 million community-dwelling Medicare beneficiaries compared the rates of adverse events and effectiveness in the 28-day period following administration of two mRNA COVID-19 vaccines (mRNA-1273 and BNT162b2). The focus on older adults makes this study highly relevant, as this population is most likely to experience adverse events from infection with or vaccination against COVID-19 infection but is so often excluded from clinical trials. The authors used a well-validated measure to assess frailty (adjudicated in over a third of the cohort), advancing our knowledge of risks and benefits of vaccination in this high-risk subgroup. The results of this study provide several important insights for healthcare providers engaged in the care of older adults. First and most importantly, adverse event rates for both mRNA vaccines were below 1%, suggesting that older adults may receive either vaccine without hesitation. Second, consistent with several previous studies, mRNA-1273 exhibited a modest advantage over BNT162b2 with respect to the occurrence of certain adverse events (including pulmonary embolism) and effectiveness in preventing COVID-19, at least during the study period. Among frail individuals, COVID-19 vaccines were less effective, the advantage of mRNA-1273 was less pronounced, and adverse event rates were higher, although still low overall. It is possible that differences in rates of adverse events between the two vaccines may relate to earlier vaccine effectiveness of mRNA-1273 over BNT162b2. In addition, the assessment of 12 potential adverse events was conducted without accounting for multiple comparisons, and reported odds ratios were close to 1. Differences between the two vaccines might have been attenuated if the authors had adjusted for multiple comparisons. While the study's findings emphasize the importance of recognizing heterogeneity in vaccine responses and health profiles among individuals, the overarching conclusion is that both mRNA vaccines are safe and effective, including among individuals with frailty.