CDC, FDA Investigating California Moderna Covid-19 Vaccine Lot With ‘Higher Than Usual’ Allergic Reactions

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Alison Durkee   Forbes U.S. Staff

Moderna Vaccin

Photo: CDC Twitter

California’s state epidemiologist urged Covid-19 vaccine providers Sunday to pause distribution of one Moderna vaccine lot while the manufacturer and federal government investigate a “higher than usual” number of allergic reactions—which are still extremely rare—temporarily stopping potentially thousands of vaccines from being administered as California faces a Covid-19 surge.


- California State Epidemiologist Dr. Erica S. Pan issued the recommendation after fewer than 10 patients who received the Moderna vaccine at a clinic in San Diego experienced severe allergic reactions and required medical attention within 24 hours of being vaccinated.

- The state said it was urging providers to use other vaccines and pause distribution of the Moderna lot “out of an extreme abundance of caution” while the manufacturer, Centers for Disease Control (CDC) and Food and Drug Administration (FDA) review the vaccine lot “and related medical information.”

- The vaccine lot included more than 330,000 doses of the Moderna vaccine distributed to 287 vaccine providers statewide, which arrived in the state between Jan. 5 and 12. 

- No other clusters of severe reactions linked to the vaccine lot have otherwise been reported.

- There is a risk of anaphylaxis and severe allergic reactions to the Covid-19 vaccine, but it is extremely rare, with Pan noting a similar vaccine to the Moderna shot has a 1 in 100,000 expected rate of anaphylaxis.

- In a statement to Forbes, a Moderna spokesperson said the company is “fully cooperating” with California’s public health department in “investigating these reported adverse effects,” and is currently “unaware of comparable adverse reactions” from any other vaccination centers using the same lot of vaccines.


1,072,959. That’s the total number of Covid-19 vaccine doses that have been administered so far in California—or approximately 2,716 doses per 100,000 people—according to the CDC. More than 3.5 million vaccines have been distributed in California, which currently has one of the lowest vaccine distribution rates of any state.


The Moderna vaccine lot pause delivers a blow to California’s vaccine distribution efforts as Covid-19 ravages the state. California currently has the second highest number of coronavirus cases per capita nationwide, with Los Angeles being a particular hotspot where officials say one in three residents have so far been infected with Covid-19. State health officials also announced Sunday that a new variant of Covid-19 has been reported across the state, different from the one first observed in the United Kingdom, which has been linked to several large outbreaks in Santa Clara, California. It is currently unclear whether the variant is more easily transmissible than other strains, however, health officials said. 

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Alison Durkee   Forbes U.S. Staff

I am a New York-based journalist covering breaking news at Forbes. I previously covered politics and news for Vanity Fair and Mic, and as a theater critic I serve as a member of the New York Outer Critics Circle.