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Moderna boss says COVID-19 vaccine not proven to stop spread of virus

Moderna’s coronavirus vaccine may not get life back to normal right away because it hasn’t yet been proven to prevent the deadly bug from spreading, the company’s top doctor says.

Research has shown that the biotech firm’s shot is effective at preventing people from getting sick with COVID-19, but there’s no hard evidence that it stops them from carrying the virus “transiently” and potentially infecting others who haven’t been vaccinated, according to Dr. Tal Zaks, Moderna’s chief medical officer.

“I think we need to be careful, as we get vaccinated, not to over-interpret the results,” Zaks told Axios in a TV interview released Monday. “When we start the deployment of this vaccine, we will not have sufficient concrete data to prove that this vaccine reduces transmission.”

“Do I believe that it reduces transmission? Absolutely yes, and I say this because of the science,” he added. “But absent proof, I think it’s important that we don’t change behaviors solely on the basis of vaccination.”

A researcher works in a lab run by Moderna.
A researcher works in a lab run by Moderna.Moderna Inc/Handout via Reuters

Zaks’ comments offer another sign that it will take time for a vaccine to bring an end to the global pandemic and help the economy recover even though drugmakers are working at a breakneck pace to produce a safe and effective inoculation.

Amanda Gorman, center, works at a COVID-19 rapid testing site at San Francisco International Airport.
Amanda Gorman (center) works at a COVID-19 rapid testing site at San Francisco International Airport.Scott Strazzante/The San Francisco Chronicle via Getty Images

Massachusetts-based Moderna revealed last week that its experimental vaccine was nearly 95 percent effective in a late-stage clinical trial. Pfizer and AstraZeneca have also reported that their shots are highly effective at warding off COVID-19.

Pfizer asked the US Food and Drug Administration to clear its vaccine for emergency use on Friday, and Moderna is expected to submit a similar request in the coming weeks. But all three companies will have to navigate the logistical challenge of distributing the vaccines around the world once regulators approve the shots.

While US officials say they plan to have millions of doses ready by the end of the year, a vaccine is not expected to be widely distributed until next spring.

People walk past an advisory sign about social distancing in Madison Square Park.
People walk past an advisory sign about social distancing in Madison Square Park.John Lamparski/Getty Images

Moderna’s stock price was roughly flat at $101 in premarket trading as of 7:57 a.m. Tuesday.