Allergic reactions to Moderna vaccine batch cause a pause from health officials

California has stopped administering one batch of the Moderna vaccine after state officials say a higher-than-usual number of possible allergic reactions were reported in Southern California.

The incidents happened at a mass drive-through vaccination site at Petco Park in San Diego.

The state didn't provide an exact number but said "fewer than 10 individuals required medical attention in one day."

In a statement, California's State Epidemiologist Dr. Erica Pan said, "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."

330,000 doses of the Moderna vaccine lot 41L20A have been distributed throughout the state including some of the following Bay Area regions:

            Santa Clara County: 21,000

            San Francisco: 8,000

            Contra Costa County: 3,700

            San Mateo County.: 3,700

            Marin County: 1,200

Of all the counties KTVU reached Monday, Marin County was the only region so far reporting it has administered all the Moderna doses from the lot in question.

"We've had no reported severe allergic reactions among those who received this lot of the Moderna vaccine," a spokeswoman said in a statement from Marin Public Health. "In fact, to date, we’ve distributed nearly 9,000 vaccine doses (both Pfizer and Moderna) within that location and have had no individuals experience severe side effects.

With the exception of Marin, most other counties KTVU reached out to told us they had not administered the doses from the Moderna lot but were notifying local providers which may have done so, saying none reported unusual vaccine responses.            

"SFDPH has not received any reports of anyone experiencing negative impacts from doses in Lot 041L20A," said a spokesperson from San Francisco's COVID Command Center.  San Francisco Public Health says its 8,000 doses have been distributed to locations including Zuckerberg San Francisco General and Laguna Honda Hospital.

Contra Costa County says of the 3,700 doses it received, it still has 3,100 that have not been administered. The other 600 were distributed to a community healthcare provider which has been notified to not use the doses while the state investigates.

Santa Clara County's Public Health Department said in a statement "to the County’s knowledge, no doses from this lot of vaccine have been administered to anyone in Santa Clara County."

County officials say they have notified providers who received the lot including Santa Clara Valley Medical Center, Stanford Health Care, and El Camino Health.

Kaiser Permanente and Sutter Health both said they pulled the vaccine as soon as instructed, but did not say how many doses of the affected lot were administered.

"To date, we have had no adverse reactions reported related to this lot," said a Sutter Health spokesperson.

"At Kaiser Permanente, we have not recorded any severe adverse reactions in patients who received vaccine from this lot. While all vaccine supply is extremely limited, this situation only affects a relatively small percentage of our supply," said a spokesperson from Kaiser Permanente in a statement. "We will be reaching out to members if we have to reschedule existing appointments and we will continue to monitor information provided by the manufacturer, CDPH, the Centers for Disease Control and the U.S. Food and Drug Administration as they investigate this situation and take additional action as needed."

Dr. Anne Liu with Stanford specializes in infectious disease and allergy and says while side effects happen, severe allergic reactions are rare.

She says she has many questions about what was reported in San Diego, saying locally the majority of reactions she has seen are common side effects and not severe allergic reactions.

"Sometimes people have a sensation that they're going to pass out. They might have a sensation they're flushing. Sometimes when we further investigate, they turn out not to be allergic," said Dr. Liu.

Dr. Liu is glad the state is investigating, but adds she still advises patients get the COVID-19 vaccine, calling it effective and important.

"It's really rare to get a reaction of this kind, even if it does happen in that rare event, we have very good treatments for it. Whereas with COVID, we don't have many good treatments," said Dr. Liu.

As for the vaccine lot being put on hold, San Francisco's Public Health Department calls it a setback, saying with no replacement doses coming in, this will affect the city's scheduled appointments this week.

"This setback comes at a time when vaccine is scarce and when SFDPH allocation from the state arriving this week is only 1,775," said a spokesperson from the COVID Command Center.