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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

That means that, at a time when about 100 million Americans have been fully vaccinated against COVID-19, the U.S. continues to rely on a patchwork network of vaccine monitoring systems that may fail to monitor a large enough swath of the population, experts told KHN.

“I’m very concerned about this,” said Goodman, who also led the FDA’s Center for Biologics Evaluation and Research, or CBER, and is now a professor of infectious diseases at Georgetown University. “I think we should be seeing that reporting on all of these vaccines. It was promised four months ago that it was happening.”

The three vaccines in use in the U.S. — produced by Pfizer, Moderna and Johnson & Johnson — were shown to be safe and effective during clinical trials of tens of thousands of volunteers.

But even the best trials aren’t large enough to capture all problems, especially rare ones, if they occur only in certain groups or outside a specific time frame. It’s important to track side effects once vaccines are distributed throughout the population — an effort known as pharmacovigilance — to ensure not only safety, but also public confidence.

Vaccine safety experts said they were concerned that the FDA scaled back a system known as the Post-Licensure Rapid Immunization Safety Monitoring network, or PRISM, long regarded as a workhorse of surveillance.

“Prior to PRISM, I felt like we were sort of in the dark ages,” Steve Anderson, director of the FDA’s Office of Biostatistics and Epidemiology, said at a 2016 workshop. “When PRISM came along, for us it was really a game changer.”


PRISM linked four large health plans in different parts of the country with eight state immunization registries. During the H1N1 pandemic, it detected signals for three adverse events possibly linked to the vaccines and was used to rule out the two that weren’t related and the one, Guillain-Barré syndrome, that was.

The system included records from nearly 40 million people, said Daniel Salmon, former director of vaccine safety at the National Vaccine Program Office. Having a large volume of records of vaccinated people “really drives your ability to figure out what’s going on,” he said.

PRISM, which was repurposed for drug safety, now contains data from about 60 million people, but it has not been used to track vaccine reactions during the COVID-19 pandemic, said Salmon, who oversaw safety monitoring for the H1N1 vaccine.

“With PRISM, we tested it in a crisis and it operated for a decade,” he said. “I was really surprised when it wasn’t used for COVID. That was why we built it.”


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