Analysis of adverse events in the elderly in the United States after COVID-19 mRNA vaccination


In a recent study published on medRxiv*, Researchers evaluated adverse events (AEs) in the elderly following ribonucleic acid (mRNA) vaccination for coronavirus disease 2019 (COVID-19).

STUDY: Evaluation of Potential Adverse Events Following COVID-19 mRNA Vaccination Among Adults Age 65 and Older: A Self-Controlled Study in the United States.  Photo credit:
Stady: Evaluation of potential adverse events after COVID-19 mRNA vaccination among adults 65 years of age and older: a self-controlled study in the United States.. Photo credit:


The US Food and Drug Administration (FDA) has approved COVID-19 vaccines under an emergency use authorization for primary vaccination and booster vaccination. This included Pfizer BNT162b2 and Moderna mRNA-1273 for individuals six months of age or older and Novavax for those 12 years of age or older. Rapid cycle analysis (RCA) is a near-real-time surveillance method for detecting elevated risk of AEs after vaccination.

This method revealed a significant association between primary immunization with BNT162b2 and pulmonary embolism (PE), acute myocardial infarction (AMI), immune thrombocytopenia (ITP), and disseminated intravascular coagulation (DIC). Another study reported the association of BNT162b2 and mRNA-1273 booster vaccination with Bell’s palsy and myocarditis/pericarditis (Myo/Peri), respectively. These hostile reagents may not present real safety concerns as RCA fails to prove that vaccines are causative.

about studying

The current study summarized the results of two independent studies on the safety of the COVID-19 vaccine. In particular, they examined the risks of PE, AMI, ITP, and DIC after primary mRNA vaccination and the risk of ITP, AMI, BP, Myo/Peri, and PE after initial mRNA vaccination. They identified the first two doses of the COVID-19 mRNA vaccine (mRNA-1273 or BNT162b2) as the initial series and the subsequent third dose as the booster dose.

The incidence of AEs due to vaccination during the putative risk period was compared to those during the control period of primary and booster vaccines among adults aged 65 years and older. The two studies (primary and booster series) included Medicare fee-for-service beneficiaries who had been vaccinated with at least one dose and who had an episode of AE during follow-up.

The primary series study analyzed post-vaccination risks for DIC, AMI, and PE during a 28-day risk window, and ITP in a 42-day risk window. The booster study assessed the risks of PE and AMI using a 28-day risk window, Myo/Peri using a 21-day risk window, and ITP and BP over a 42-day risk window.

Subjects were followed until the end of the observation/study, fourth vaccination, or death. The medical records of the cases from the two studies categorized as valid, unspecified, or non-cases were reviewed. The conditional Poisson regression method was applied to calculate an incidence rate ratio that compares rates for each AE in the risk and control intervals.

the findings

More than 3.3 million individuals have completed the initial series, and 6.1 million have been boosted with the mRNA vaccine. The number of cases for AMI was 3,653 (primary series) and 16,042 (enhanced), patient’s PE was 2,470 (primary) and 5,085 (enhanced), DIC was 254 (primary only), BP was 3,268 (enhanced only) , ITP was 1,085 (basic) and 88 (enhanced), and myo/berry was 1,295 (enhanced only).

BNT162b2 recipients were younger, more likely to live in a nursing home, and less likely to live in a rural area than mRNA-1273 recipients in both studies. In the primary series study, DIC and AMI showed elevation death rate from 67% and 34%. The risk of AMI was significantly increased after initial vaccination with BNT162b2.

However, this effect was small after adjusting for seasonality or misclassification of outcomes and excluding individuals previously infected with COVID-19. The risk of post-BNT162b2 AMI enhancer was not high. The risk of AMI did not increase significantly after the initial or booster mRNA-1273 immunization.

The risk of inpatient PE increased significantly after primary BNT162b2 immunization, which remained significant in the adjusted analysis. By contrast, it was significantly reduced after BNT162b2 booster vaccination. The primary series study revealed no significant increase in inpatient risk after vaccination with mRNA-1273, whereas the risk was significantly reduced after booster vaccination with mRNA-1273.

The risk of blood pressure increased significantly after booster vaccination with BNT162b2 but not with mRNA-1273 and was consistent in the adjusted analyses. The risk of ITP did not increase after primary/booster vaccination with an mRNA vaccine. Likewise, the risk of DIC did not increase after vaccination. The risk of myo/berry was not significantly increased for either vaccine.


In summary, the researchers found no significant increases in the risks of DIC, Myo/Peri, AMI, and ITP after COVID-19 mRNA vaccination in the elderly US population. Results have been inconsistent for PE. BP risks were slightly increased after mRNA vaccination. Overall, these results confirm the safety of mRNA vaccines against COVID-19 and are consistent with the conclusion that the benefits of vaccination outweigh the risks.

*Important note

medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, directing clinical practice/health-related behaviour, or treated as hard information.


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