California officials directed COVID-19 vaccine providers on Jan. 17 not to administer any doses from a batch of more than 330,000 that was circulated across the state.
The reason was a "higher-than-usual number of possible allergic reactions," California State Epidemiologist Dr. Erica Pan said in a statement.
The doses were produced by Moderna.
Moderna, the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA) are investigating.
"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," Pan said.
Moderna didn't immediately respond to repeated requests by The Epoch Times for comment.
The possible allergic reactions are believed to have all occurred in people within 30 minutes after being injected. The CDC recommends vaccine providers implement a 15-minute observation period for people getting one of the COVID-19 vaccines, and a 30-minute observation period for people who previously have had an allergic reaction to vaccines or injectable therapies.
Data from the manufacturers of the two authorized COVID-19 vaccines demonstrate that the known and potential benefits of this vaccine outweigh the known and potential harms of becoming infected with COVID-19, according to the CDC.