Small-magnitude differences in risk of adverse events identified between the BNT162b2 and mRNA-1273 across 38 weeks follow-up

1. Among a large cohort of US veterans, the 38-week risks of adverse events were low in both vaccine groups, although risks were lower for recipients of the mRNA-1273 vaccine compared to the BNT162b2 vaccine.

2. Within 14 days of the first dose, there were few differences in risk of adverse events between the BNT162b2 and mRNA-1273 vaccine and small-magnitude differences within 42 days of the first dose.

Evidence Rating Level: 2 (Good)

Study Rundown: The mRNA vaccines – BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) – have been found to have a low incidence of adverse events in randomized trials of small homogenous cohorts with short-term follow-up. There is lack of data on vaccine comparative efficacy and safety over longer follow-up and in larger and more diverse populations. This cohort study used data from the US Department of Veterans Affairs, to compare the safety profiles of theBNT162b2 and mRNA-1273 vaccines during 38 weeks of follow-up and in subgroups defined by age and race. Key adverse events evaluated included neurologic and hematologic events, hemorrhagic stroke, ischemic stroke, myocardial infarction, other thromboembolic events, myocarditis or pericarditis, arrhythmia, and kidney injury. Among 433 672 US veteran recipients of the BNT162b2 and mRNA-1273 vaccines, BNT162b2 had an excess per 10 000 persons of 10.9 ischemic stroke events, 14.8 myocardial infarction events, 11.3 other thromboembolic events, and 17.1 kidney injury events over 38 weeks follow-up. A limitation of this study was ensuring that risk factors and demographics were comparable for both vaccine groups for accurate comparative efficacy.

Click to read the study in JAMA Internal Medicine

Relevant Reading: Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine

In-Depth [retrospective cohort]: This cohort study included 433 672 US veterans (median age [IQR], 69 [60-74] years; 93% male; 20% Black) who received a first dose of the BNT162b2 or mRNA-1273 vaccine in 2021, matched 1:1 according to risk factors. Both BNT162b2 and mRNA-1273 vaccines had low estimated 38-week risks of adverse events. Compared to mRNA-1273, the BNT162b2 group had an excess per 10 000 persons of 10.9 events (95%CI, 1.9-17.4 events) of ischemic stroke, 14.8 (95%CI, 7.9-21.8 events) of myocardial infarction, 11.3 (95%CI, 3.4-17.7 events) of other thromboembolic events, and 17.1 (95%CI, 8.8-30.2 events) of kidney injury. Greater magnitude of risk difference between vaccine groups were observed for ischemic stroke in older and White persons, kidney injury in older persons, and other thromboembolic events in Black persons.

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