The quick detection of an ultra-rare blood clotting reaction in some Covid-19 vaccine recipients showed the power of a federal warning system for vaccine safety issues, but experts worry that blind spots in the program could hamper detection of other unexpected side effects.

Before the pandemic began, the Food and Drug Administration had scaled back a program it used successfully to track adverse events during and after the 2009 H1N1 influenza pandemic, and the agency is still ramping up its replacement, said Dr. Robert Chen, scientific director of the Brighton Collaboration, a nonprofit global vaccine safety network.

source: nbcnews.com