On Monday, Pfizer asked the U.S. Food and Drug Administration for emergency authorization for the drugmaker’s new Omicron booster targeting the BA.4 and BA.5 strains. Moderna followed on Tuesday with its own application to the FDA for emergency authorization for its BA.5 booster.
But unlike previous applications, Pfizer’s and Moderna’s filings are missing one piece of information: clinical trial data of their vaccines.
That’s deliberate. In June, the FDA asked vaccine manufacturers to start developing BA.4 and BA.5 boosters for a fall vaccination campaign. To help the drugmakers hit that fall deadline, the FDA said the companies did not need to include data from a clinical trial.
“It’s very similar to what we do with influenza strain changes where there will be a couple of amino acids difference,” Dr. Peter Marks, who helps oversee vaccines for the FDA, told Reuters in late June. “We don’t expect any difference in the safety that we’re going to see,” he said.
Pfizer’s and Moderna’s applications this week still include important information, such as data on how earlier Omicron boosters in development performed against previous strains, as well as preclinical data for the BA.5 booster.
Preclinical trials are conducted in human cell cultures or in animals, and are used to test a drug’s effectiveness and safety. After that, the drug proceeds to clinical trials, where it is administered to human subjects. Previous clinical trials of COVID vaccines took months to complete, significantly faster than the years it takes to complete a clinical trial for most drugs.
Pfizer’s and Moderna’s Omicron booster filings do not include the clinical trial data included in earlier vaccine applications. Moderna said a clinical trial of its BA.5 booster is currently underway, while Pfizer said its trial is expected to start this month.
The FDA’s new exemption is an effort to speed up the approval process so updated COVID vaccines can keep pace with new variants, which are emerging so rapidly they risk making boosters out-of-date by the time the jabs reach the market. Both Pfizer and Moderna have been working on boosters that target BA.1—the original Omicron strain—since the beginning of the year. The U.K. approved vaccines that target BA.1 last week. But BA.1 has vanished from the U.S., outcompeted by newer Omicron strains like BA.4 and BA.5. The latter now makes up 88.9% of cases in the U.S., according to the U.S. Centers for Disease Control and Prevention, up from 2.5% just three months ago.
And there are already new variants of concern emerging in the U.S. and elsewhere. While BA.5 is by far the most dominant strain in the U.S., both BA.4.6 and BA.2.7.5 have managed to gain ground, pushing out other strains. Experts are now urging the development of a universal vaccine that can protect against current and future strains of the COVID-19 virus.
For now, a faster process “will help us get ahead of things,” said Marks to Reuters in June. But some experts criticize the FDA’s change, fearing that preclinical studies might not give a good indication of how effective a vaccine is in humans.
On Monday, Pfizer said that its booster would be available to ship “immediately” once the FDA approves it. Moderna said on Tuesday that it expects to have boosters ready by September.
But health experts recommend that those eligible for a second booster should get one now, rather than wait for updated boosters to be available.