SACRAMENTO (CBS SF) — A top state health official has recommended halting distribution of a specific lot of the Moderna COVID-19 vaccine after “a higher-than-usual number of possible allergic reactions” to it at a San Diego mass vaccination site.

Dr. Erica Pan, the state’s top epidemiologist, issued the warning about Moderna Lot 041L20A on Sunday night.

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“Our goal is to provide the COVID vaccine safely, swiftly and equitably,” Pan said in the statement. “A higher-than-usual number of possible allergic reactions were reported with a specific lot of Moderna vaccine administered at one community vaccination clinic. … Out of an extreme abundance of caution and also recognizing the extremely limited supply of vaccine, we are recommending that providers use other available vaccine inventory and pause the administration of vaccines from Moderna Lot 041L20A until the investigation by the CDC, FDA, Moderna and the state is complete. We will provide an update as we learn more.”

Alameda County health officials said they were halting distribution of doses from the lot.

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In Santa Clara County, public health officials say they’ve isolated 21,800 doses of the Moderna vaccine. Public health officials say it does not appear that any vaccinations were given from the lot in question.

“There are good safeguards in both the Pfizer and Moderna vaccines. They include a minimum observation time of 15 minutes. And the reason that 15 minutes was chosen is because these severe allergies usually happen within minutes,” says Dr. Peter Chin-Hong, an infectious disease expert with UCSF.

Health officials say more than 330,000 doses from the lot had been distributed to 287 providers across the state. The shipments arrived in California between Jan. 5 and 12. The state has not been notified of any other cluster or individual events related to this lot.

“There are not immediate replacement doses during the pause in addition to pending orders scheduled for shipment in the next few days,” officials said in a news release.

“The manufacturer, CDC and FDA are promptly reviewing the lot and related medical information. No additional clusters have been reported. Their investigation continues, and we expect to learn more this week,” the statement continued.

California Department of Public Health spokesman Darrel Ng told the Los Angeles Times that the apparent allergic reactions occurred at San Diego County’s drive-through mass vaccination site at Petco Park.

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Severe allergic reactions were believed to be exceedingly rare in both the Moderna and Pfizer vaccines. The rate of anaphylaxis in the Moderna vaccine was expected to be about one in every 100,000, officials said.