Why California Put a Pause on a Single Lot of the Moderna COVID-19 Vaccine

• Health officials are to stop using a specific lot of Moderna vaccine.
• Fewer than 10 people developed allergic reactions after getting this vaccine.
• All people affected were successfully treated.

Health officials in California have asked healthcare providers to pause vaccinations from a single lot of the Moderna vaccine after six people in San Diego experienced severe allergic reactions after receiving the shot.

The people required medical attention after receiving the shot, according to a statement from the California Department of Public Health (CDPH).

There have been no other clusters or adverse events linked to the lot (Moderna Lot 041L20A).

More than 330,000 vaccine doses were distributed to 287 providers across California in early January.

The lot contained a total of 1,272,200 doses, most of which were shipped across the country, according to a Moderna statement.

Thousands of those doses have already been administered.

Severe allergic reactions to vaccines are rare, with vaccine-related anaphylaxis occurring in approximately 1 in 100,000 people, according to the Centers for Disease Control and Prevention (CDC).

However, the vaccine is new, and health officials have been closely monitoring allergic reaction rates.

But out of an abundance of caution, the CDPH recommends that California providers administer other batches until the state, Moderna, CDC, and Food and Drug Administration (FDA) investigate the lot in question.