SAN JOSE, Calif. (KRON) — KRON4 is learning more about the order to halt COVID-19 vaccinations using a suspect batch of the Moderna vaccine.

At least 300,000 vaccinations have been put on hold because some people have sought medical for possible severe allergic reactions.

State health officials urged a halt to vaccinations using a Moderna vaccine as a cluster of people sought medical help after suffering severe side effects in Southern California. 

More than 300,000 doses of the vaccine have now been set aside pending tests. 

Santa Clara County has received just over 21,000 doses of the vaccine from the suspect batch. 

Local health care providers receiving the vaccine so far include Valley Medical Center, El Camino Health and Stanford Health Care.

None of the vaccine has been given in the county prior to the state calling for an investigation. 

Alameda County health official said vaccine from the same batch had been administered there but no serious side effects have been reported so far

Halting vaccinations pending more tests is the right call, says Stanford Medicine infectious disease expert Dr. Hayley Gan.

“When the body sees something foreign, that is time to respond to, sometimes it’s part of the response. We know it can happen with vaccines so we’re all prepared to deal with it. If you administer vaccines, that is part of your administration protocol,” Dr. Gan said.

The vaccine comes under scrutiny after about ten people experienced a severe allergeic reaction after receiving the shot at a San Diego vaccination site. 

They required medical attention. 

That amounts to what health officials consider a “cluster” and needs to be looked into, says Stanford’s Dr. Gan.

“So that’s why I think taking a pause and trying to figure out was it just an issue with that particular center or was there something more global within that large, as you said, large scale batch that we need to investigate first,” Dr. Gan said.

The vaccine in question represents about 10-percent of California’s supply and about 15-percent of what Santa Clara County has recieved thus far.