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Data Shows Pfizer's COVID Vaccine To Be 90% Effective - But What Does That Mean?

MINNEAPOLIS (WCCO) -- On Tuesday morning, drug company Pfizer announced its COVID-19 vaccine is working better than experts had expected.

Data suggests it is 90% effective in preventing the novel coronavirus. But, what exactly does that mean?

Dr. Timothy Schacker, vice dean for research at the University of Minnesota Medical School, says he's excited about the news, but he's not dancing in the streets just yet.

"I have cautious optimism [laughs]," Schacker said. "These are preliminary results, and you have to take that into consideration."

The data, from an independent monitoring board, is preliminary, but Pfizer CEO Albert Bourla told CNN Monday, "90% is a game-changer."

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Some participants in the Pfizer study were given a placebo, while others were given a vaccine.

"Ninety-percent of the people who get the vaccine will mount an immune response that is protected in some way," Schacker said.

According to the Centers for Disease Control and Prevention, efficacy for the measles vaccine is around 97%. It's between 50% to 60% on average for influenza. Compared to more stable coronaviruses, influenza has a high mutation rate.

Right now, there are four late-stage COVID-19 vaccine trials in the United States: Johnson and Johnson, AstraZeneca, Moderna and Pfizer.

Pfizer said it does expect to apply for Emergency Use Authorization from the Food and Drug Administration once it completes two months of safety data. That could happen later this month.

"Thus far, the vaccines have not given us any signal that there are serious or significant safety concerns," Schacker said.

This does not mean that the vaccine will become widely available in the very near future. According to Patsy Stinchfield, senior director of infection prevention and control at Children's Minnesota and a liaison representative for the CDC's Advisory Committee on Immunization Practices, healthcare workers will likely get the first doses of the vaccine in December or January.

The vaccine is not expected to be available to the general public until late spring.

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