The vast majority of reported reactions were mild, such as headaches and fatigue.
In clinical trials, the Pfizer and Moderna COVID-19 vaccines demonstrated low rates of serious adverse events. Now, real-world data from the first month of vaccine administration in the United States corroborates that data.
A new CDC report looks at the figures for VAERS, a government-monitored vaccine safety portal where healthcare professionals in the U.S. are required to report adverse events after vaccinations.
In a month in which nearly 14 million doses of vaccine were administered, only about 7,000 reports were sent to VAERS – 91% of which described mild events, such as headache, fatigue and dizziness.
Anaphylaxis, a reaction to the vaccine that received wide media coverage, was considered unusual: 62 cases in total were reported, at a rate of 4.5 per million doses – comparable to the rate of anaphylaxis with other common vaccines.
Among the 14 million doses, 113 deaths were reported to VAERS; 78 from long-term care facilities and 35 off-site – and so far, none of these deaths have been directly linked to the vaccine.
The data is not entirely surprising, says William Schaffner, MD, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center.
“The scope of the safety assessment has been better than any other licensed vaccine we use in the United States,” he told ABC News. “Clinical trials for both vaccines were very extensive and both showed very low rates of serious adverse reactions.”
The CDC also collected data reported by patients from v-safe, a smartphone app for voluntarily reporting adverse events. Of the 1.6 million vaccinees who participated, the majority reported mild side effects, such as pain at the injection site, fatigue, headache and chills. These symptoms were reported as more prominent on the first day after the injection – and worse with the second dose – but improved with each subsequent day, disappearing on day 3 or 4.
The app also collected data on the state of pregnancy, and the nearly 11,000 women who reported being pregnant will be followed up on a dedicated record.
CDC data is limited, as it relies heavily on self-reported data. For example, in both the VAERS and v-safe reports, the majority of adverse events were seen in women. But, as Schaffner describes, this does not necessarily mean that women are more prone to reactions.
“I am more inclined to believe that it is a reporting bias,” he said, describing the well-documented difference in the use of health care between men and women. “Women are more inclined to seek medical attention and more inclined to report illness.”
Those who judged the pace of vaccine release to be too hasty can be reassured by the CDC reports, said Schaffner.
“Now that we have data very well analyzed, from a really comprehensive series of surveillance systems, we can go beyond very large studies and say, look, we are doing this in the real world, among your friends and neighbors,” he said. “This vaccine remains very, very safe.”
Eric Silberman, MD, an internal medicine resident doctor at Northwestern Memorial Hospital, is a contributor to ABC News Medical Unit.