SACRAMENTO – California State Epidemiologist Dr. Erica S. Pan issued the following statement today recommending providers pause the administration of lot 41L20A of the Moderna COVID-19 vaccine due to possible allergic reactions that are under investigation.

"Our goal is to provide the COVID vaccine safely, swiftly and equitably," said Dr. Pan. "A higher-than-usual number of possible allergic reactions were reported with a specific lot of Moderna vaccine administered at one community vaccination clinic. Fewer than 10 individuals required medical attention over the span of 24 hours. 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."

All appeared to be experiencing a possible severe allergic reaction during the standard observation period – a type of adverse event that the CDC reports some people have experienced when receiving a COVID-19 vaccine.

While no vaccine or medical procedure is without risk, the risk of a serious adverse reaction is very small. While less data exists on adverse reactions related to the Moderna vaccine, a similar vaccine shows that the expected rate of anaphylaxis is approximately 1 in 100,000.

More than 330,000 doses from this lot have 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.

The manufacturer, Centers for Disease Control and Prevention (CDC) and U.S. Food and Drug Administration (FDA) are reviewing the lot and related medical information.

Below is the recommendation sent to providers today:

Recommendation that Providers Pause Administration of Moderna's COVID-19 Vaccine Lot 041L20A

This week, a higher-than-usual number of adverse events were reported with a specific lot of Moderna vaccine (Moderna Lot 041L20A) administered at one community vaccination clinic. Fewer than ten individuals required medical attention over the span of 24 hours. Follow up investigation of outcomes of these individuals is underway, and more information will be forthcoming.

All appeared to be experiencing a possible severe allergic reaction during the standard observation period – a type of adverse event that the CDC reports some people have experienced when receiving a COVID-19 vaccine. The vaccine site switched to another lot of Moderna vaccine after closing for a few hours.

More than 330,000 doses from this lot have been distributed in the state, and we have not been notified of any other cluster or individual events related to this lot.

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.

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 administration of vaccines from Moderna Lot 041L20A until the investigation is complete.

There are not immediate replacement doses during the pause in addition to pending orders scheduled for shipment in the next few days.

We expect to provide an update this week as we learn more.

Providers of COVID-19 vaccine should continue their routine precautions to recognize and manage allergic reactions and potential adverse events.

https://www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html