The U.K., The EU And The WHO Have All Authorized AstraZeneca’s Covid-19 Vaccine—Why Hasn’t The U.S.?

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It’s been a bumpy road for a new Covid-19 vaccine developed by pharma giant AstraZeneca and Oxford University. On February 15, the vaccine received an Emergency Use Listing designation from the World Health Organization, allowing it to begin distribution in low- and middle-income countries. In January, the vaccine was granted approval for use in the European Union, following a December 30 decision by the U.K. to authorize the vaccine. Yet for all its recent wins, the vaccine is still in limbo in the U.S. where there are no concrete plans for emergency authorization, despite desperate need for more Covid-19 vaccines. 

The wait has angered many pundits on social media, who call for immediate approval for the AstraZeneca vaccine. “I think we should approve AstraZeneca for [people] under 45 ASAP,” wrote Derek Thompson, an author at The Atlantic, “Expanding vax supply would save lives, and the benefits outweigh the risks.” 

Matthew Yglesias, a writer on Substack who previously worked at Vox, wrote: “Despite the botched clinical trial, nobody seems to actually doubt that the Oxford/AstraZeneca vaccine approved by the WHO works.”

So, why hasn’t the FDA authorized it yet? The main reason is simple: the company hasn’t applied for emergency-use authorization yet. The process must be initiated by the company—regulators can’t get the ball rolling themselves.

In the U.S. there are several things holding the AstraZeneca/Oxford vaccine back, says Andrew Berens, an analyst at SVB Leerink. “I think a large part of the reason it hasn’t gotten an EUA in the U.S. yet is because the FDA wants to see the U.S. trial that’s ongoing,” he says. Berens estimates that the trial data will be available sometime in the first half of this year. A spokesperson for the company said this data would be available in “the coming weeks,” but wouldn’t provide a more concrete time line. 

“Manufacturing is really tough for vaccines,” he says. “It’s complicated, and the bar is very high.”

AstraZeneca’s vaccine is different from the two vaccines that are currently authorized for use in the U.S., created by Moderna and Pfizer/BioNTech. Both of those vaccines use mRNA technology, which makes cells inside the body produce fragments of the virus that trigger the immune system. The AstraZeneca vaccine works by using a modified version of a virus for the common cold that infects chimpanzees. This virus acts as a delivery service that delivers DNA into a patient’s cells. This DNA gives instructions to the cell to turn it into mRNA, which programs cells to produce fragments of the virus that trigger an immune response. This immune response in turn prepares the body to attack the Covid-19 virus if a person is infected.

Clinical trials have shown that the vaccine is 82% effective at preventing the most common strain of SARS-CoV-2 after two doses, but it is much less effective at protecting against some of the other variants currently circulating. Like the Pfizer and Moderna vaccines, it is extremely effective against severe disease, hospitalization and death—no one who has gotten the AstraZeneca vaccine so far has died of Covid-19. And due to the hardier nature of the vaccine, it can be stored in a normal refrigerator instead of the ultracold temperatures that both mRNA vaccines require. 

Despite these advantages, clinical trials for the AstraZeneca vaccine have been plagued by starts and stops. Last fall, all global phase 3 clinical trials of the vaccine were suddenly halted after a patient in the U.K. showed symptoms of a serious neurological disorder called transverse myelitis. After a 45-day pause, the trial resumed in the U.S., but the delay put AstraZeneca more than a month behind its competitors. 

The stoppage isn’t the only hurdle the AstraZeneca vaccine has faced. South Africa had planned to widely distribute the vaccine, but a recent, not yet peer-reviewed study claimed the vaccine was largely ineffective at preventing the 501Y.V2 variant that has been circulating widely in that country. On February 10, South Africa announced it would stop using the AstraZeneca vaccine and instead switch to using a Covid-19 vaccine made by Johnson & Johnson. The country is now reportedly asking the Indian manufacturer of the vaccine to take back one million doses of the vaccine. Also this month, regulators from the European Commission raided one of the company’s vaccine manufacturing sites in Belgium after production problems led the company to say that only half of the promised doses would be delivered to the EU this quarter. 

Berens says that manufacturing capability will be one of the key things that the FDA looks at when deciding whether to authorize the vaccine. “Manufacturing is really tough for vaccines,” he says. “It’s complicated, and the bar is very high.” It isn’t yet known where the vaccine doses for the U.S. will be made. 

All of these setbacks have influenced the company’s progress in the vaccine race, putting it behind Pfizer, Moderna and Johnson & Johnson, and until it has positive phase 3 data from its U.S. clinical trials, AstraZeneca won’t submit an EUA application to the FDA. Once AstraZeneca applies, experts at the agency will review all the vaccine data in a process that can take several weeks and includes public committee hearings. Only after all that has been finished could another Covid-19 vaccine be available in the U.S. 

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