Public health officials across California must rethink their COVID vaccine distribution plans after learning Wednesday that future U.S. shipments of the long-awaited, single-dose Johnson & Johnson vaccine have been abruptly halted over quality concerns.

The news couldn’t have come at a worse time as California dramatically expands vaccine eligibility to people 50 and older starting today. All Californians 16 and older become qualified on April 15.

California was allocated 572,700 doses of Johnson & Johnson vaccine for next week. That shipment will still arrive.

“We are working with the federal government to learn more about potential impacts,” California Department of Public Health spokesman Darrel Ng told CalMatters Wednesday. “Maintaining the highest standards during vaccine production to ensure safe and effective vaccines is a paramount concern.”

Up to 15 million doses of the Johnson & Johnson vaccine, also called the Janssen vaccine, reportedly were ruined in recent weeks because of quality-control problems at a Baltimore manufacturing plant, the New York Times reported Wednesday.

Production cannot restart until U.S. regulators complete an investigation. Johnson & Johnson said in a press release that “one batch of drug substance” used in manufacturing the vaccine “did not meet quality standards.”

All current doses of the Johnson & Johnson vaccine are considered safe as they were produced in a Netherlands facility approved by federal regulators, the Times reported.

The single-dose vaccine, which requires only refrigeration and not freezing, has been viewed as critical to speeding vaccinations in California and across the nation in a race against emerging COVID-19 variants.

Although Johnson & Johnson doses currently comprise a smaller part of California’s vaccination program than the Moderna and Pfizer vaccines, state officials expected supplies to increase significantly. The company projected that 100 million doses would become available nationwide by mid-year.

This is not the first time Johnson & Johnson doses have been delayed: Earlier in March, they were not distributed nationwide as planned because manufacturing was slower than expected, Reuters reported.

Public health officials also are trying to overcome the skepticism of some Americans about the vaccine, which the FDA says is safe and effective in preventing death and serious disease. Studies show it does not provide as much protection as the Pfizer and Moderna vaccines.

Last month, five of California’s top government doctors received the Johnson & Johnson shot to boost public confidence. Public health officers from nine Bay Area counties also jointly expressed their confidence in the single-dose vaccine, noting — ironically, in retrospect — that “the best vaccine is the one you can get the soonest.”

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