California's state epidemiologist, Erica Pan, MD, told healthcare providers Jan. 17 to stop using a batch of Moderna's COVID-19 vaccine after a "higher than usual" number of severe allergic reactions took place at a vaccination clinic in San Diego.
Dr. Pan said that "out of an extreme abundance of caution," providers should stop using doses of the vaccine from the affected lot until federal, state and company officials finish an investigation.
Fewer than 10 people required medical attention over the span of 24 hours, Dr. Pan said in a statement. All appeared to be experiencing a possible severe allergic reaction during the standard observation period.
"That number, clustered together, was slightly higher than expected for the time period," Eric McDonald, MD, San Diego County's director of epidemiology, told the Los Angeles Times.
The vaccination site switched to another batch of Moderna vaccines after closing for a few hours, Dr. Pan said.
No other issues with the batch of Moderna vaccines have been reported. More than 330,000 doses from the batch were distributed to 287 providers in California between Jan. 5 and Jan. 12, according to Dr. Pan. Moderna, the CDC and the FDA are reviewing the batch and related medical information and more information is expected this week.
Moderna is unaware of comparable clusters of adverse events from other vaccination centers that may have administered vaccines from the same batch, or from other Moderna batches, the drugmaker said Jan. 19.
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