CDC study finds one shot of Pfizer, Moderna vaccines confers 80 percent immunity

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Top health officials continue to urge Americans to return for the second shot

A new CDC study has found that just one dose of the vaccines produced by either Pfizer and Moderna are 80 percent effective in preventing COVID-19 infections.  

The study, which was conducted among nearly 4,000 vaccinated health care workers with no previous documentation of COVID-19 infection, found that one shot of either vaccine conferred significant immunity two weeks later. Health officials still recommend getting the full two shots of the vaccines, as the study found that  the effectiveness rose to 90 percent two weeks after the second dose. 

“These findings indicate that authorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection, regardless of symptom status, among working-age adults in real-world conditions,” the CDC wrote. “COVID-19 vaccination is recommended for all eligible persons.”

Experts say the study’s findings could help stretch the vaccine supply and get more Americans at least partially vaccinated at a faster pace. However, Dr. Anthony Fauci and other top health officials have said that Americans should definitely prioritize returning for a second shot. 

The second dose of the vaccines from both Pfizer and Modern contain a host of “virus-specific neutralizing antibodies that is almost 10 growth fold greater than after the first dose,” Dr. Paul Offit, a voting member of the FDA’s Vaccines and Related Biological Products Advisory, told CNBC. 

Offit said the study’s findings are generally “good news,” but he noted that other studies show that the second shot appears to instill longer-lasting immunity to the virus. 

CDC director warns of ‘impending doom’

The findings come as health officials express concern about a reversal in the downward trend of COVID-19 infections. During a press briefing on Monday, CDC Director Dr. Rochelle Walensky said the U.S. is heading toward “impending doom” as daily infections rise again

“We have so much to look forward to, so much promise and potential of where we are and so much reason for hope, but right now I’m scared,” Walensky said. 

She said cases have risen over the last week or so -- a marker that typically predicts that they will “surge and surge big” shortly thereafter. Walensky urged Americans to persevere and get vaccinated as soon as they are eligible. 

“I’m speaking today not necessarily as your CDC director and not only as your CDC director, but as a wife, as a mother, as a daughter, to ask you to just please hold on a little while longer,” she said.

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