Comparing mRNA COVID-19 Vaccines in Seniors

Seniors given Moderna’s COVID-19 vaccine, mRNA-1273, were found to have a 14% lower risk of diagnosed COVID-19 compared to those administered the Pfizer-BioNTech vaccine, BNT162b2, according to a new study.

The findings were published in JAMA Network Open yesterday.

The study population was limited to Medicare fee-for-service (FFS) beneficiaries aged 66 years or older who received an mRNA vaccine as their first COVID-19 vaccine dose between December 2020 and July 2021.

Investigators analyzed data from 6 million patients, with the average age being 76, 59.4% were women, 86.5% were White, with 28 days of follow-up. The study's investigators conducted the research as part of the IMPACT Collaboratory project that allowed massive monitoring of the long-term safety and effectiveness of the vaccines for Medicare beneficiaries in collaboration with CVS and Walgreens.

Looking at the safety profile, the Moderna vaccine was associated with a 4% lower risk of pulmonary embolism and a 2% lower risk of thromboembolic events compared to the Pfizer-BioNTech vaccine.

“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,” investigators wrote.

The investigators also acknowledged some differences in the patients who were vaccinated.

“…Individuals who received BNT162b2 were older (aged ≥90 years: 7.2% vs 5.2%; standardized difference, 0.09), were more likely to be Black (5.8% vs 4.8%; standardized difference, 0.05), and were more likely to be categorized as frail (6.8% vs 5.1%; standardized difference, 0.07),” the investigators wrote.

“Because the risk of adverse events following natural infection exceeds that of either mRNA vaccine, vaccination with any available product should be prioritized,” the investigators wrote. “Nonetheless, mRNA-1273 was associated with a slightly lower risk of pulmonary embolism and other adverse events compared with BNT162b2. Because individuals who received mRNA-1273 also had a lower risk of diagnosed COVID-19, the reduced risk of adverse events in this vaccine group may represent the benefits of vaccination with a more effective product. 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.”