New Study Shows No Serious Health Effects from Pfizer, Moderna Vaccines

No serious health effects could be linked to the Pfizer and Moderna COVID-19 vaccines, according to a new study published in JAMA, which involved the HealthPartners Institute. The study did not look at the Johnson & Johnson vaccine.

The study included 6.2 million patients and looked at 23 potential side effects including neurological disorders such as encephalitis/myelitis, seizures, and Guillain-Barre syndrome; cardiovascular problems such as acute myocardial infarction, stroke, and pulmonary embolism; and others such as Bell’s palsy, appendicitis, anaphylaxis, and multisystem inflammatory syndrome.

"Our data validates the safety profile of these mRNA vaccines,” said Elyse Kharbanda, MD, senior investigator with HealthPartners Institute and co-author on the study. “Vaccines are our best hope for returning to more normal lives. They help prevent COVID-19 and we can feel even more confident that they’re safe.”

The study identified 34 cases of heart inflammation in patients aged 12 to 39 years. Eighty-five percent of these cases occurred in males. Eighty-two percent of these people were hospitalized for a median of one day. The authors calculated that among patients aged 12 to 39 years, there is a slight risk of 6.3 additional myocarditis cases per million doses during the first week after vaccination.

The JAMA study involved eight large health systems, including HealthPartners, that make up the Vaccine Safety Datalink (VSD). VSD is a research network that conducts post-marketing surveillance of vaccines licensed and used in the U.S. The other health systems include five Kaiser Permanente regions, the Marshfield Clinic, and Denver Health, all in collaboration with the Centers for Disease Control and Prevention, which funded the work.