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Detecting rare blood clots was a win, but US vaccine safety system still has gaps

JoNel Aleccia, Kaiser Health News on

Published in News & Features

A newer system, called the Biologics Effectiveness and Safety System, or BEST, was started in 2017, but only recently began monitoring data weekly for 15 pre-specified adverse events among Medicare recipients. It will be expanded to include commercial databases starting by the end of June, according to Capobianco, the FDA spokesperson.

A search for possible cases of the rare condition linked to the J&J vaccine began in mid-April and will be expanded in the next few weeks, she added.

FDA officials said PRISM’s capabilities have been incorporated into BEST, which can examine data from 100 million people. Experts told KHN that it has not been used extensively to monitor post-vaccination effects, but Capobianco said: “We disagree.”

“BEST is built as a state-of-the-art active surveillance system,” she wrote.

The concern is that officials have leaned heavily on VAERS, a “passive” system that relies on reports from patients and health care providers to flag issues after vaccination that may or may not be related to the shots. A robust “active” surveillance system can search large volumes of patient care records to compare rates of adverse events in people who received vaccines with those who didn’t.

In addition, some vaccine safety experts point to a lack of clear authority in the area. The Trump administration shut down the NVPO, a federal office with expertise in monitoring vaccine safety, merging it into a government agency focused on infectious diseases.

As a result, monitoring of COVID-19 vaccine safety is fragmented among federal agencies, said Salmon, who now directs the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health.

“There is no single person in charge,” he said. “You need to have somebody in charge.”


Biden administration officials have praised the nation’s vaccine monitoring system, pointing out that it flagged the Johnson & Johnson problems within weeks of the vaccine’s rollout. Federal officials paused distribution to assess additional cases and next steps. (They were helped by the fact that European regulators had found similar problems in another vaccine.)

“VAERS performed exactly as intended in this case,” said Dr. Tom Shimabukuro, head of the CDC’s COVID-19 Vaccine Task Force.

That’s true, said Dr. Steven Black, co-director of the Global Vaccine Data Network. Still, he noted, there’s room for improvement, particularly more funding and better collaboration.

“This is a safeguard for our population,” Black said. “Whether it’s for the flu vaccines or the COVID vaccines, you need to have a viable and strong system. Just because we think they’re safe doesn’t mean you don’t need systems in place to back up that opinion.”


(KHN (Kaiser Health News) is a national newsroom that produces in-depth journalism about health issues. Together with Policy Analysis and Polling, KHN is one of the three major operating programs at KFF (Kaiser Family Foundation). KFF is an endowed nonprofit organization providing information on health issues to the nation.)

(c)2021 Kaiser Health News Distributed by Tribune Content Agency, LLC