The Covid-19 vaccines developed by Pfizer/BioNTech and Moderna are 94% effective at preventing hospitalizations in adults 65 and older who have been fully vaccinated, according to a recent Morbidity and Mortality Weekly Report from CDC, offering the best real-world evidence so far of vaccine effectiveness at reducing U.S. hospitalizations.

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Details on the report

For the report, researchers looked at 417 patients admitted to 24 hospitals in 14 states between January 1 and March 26, comparing those who had received Covid-19 vaccines with those who had not.

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They found that, among adults 65 and older who had received both shots of their Covid-19 vaccine at least two weeks previously, the risk of hospitalization from Covid-19 dropped by 94%. Meanwhile, adults 65 and older who were partially vaccinated—that is, who had received only one shot in the two-dose regimen at least two weeks prior to their admission—saw their hospitalization risk drop 64%.

CDC found that no meaningful difference in hospitalization rates among people for whom less than two weeks had elapsed since their first vaccine dose. According to the researchers, this highlights "the continued risk for severe illness shortly after vaccination, before a protective immune response has been achieved." As a result, partially vaccinated adults need "to continue physical distancing and prevention behaviors," the researchers wrote.

CDC Director Rochelle Walensky said the findings of the report are "encouraging and welcome news for the two-thirds of people aged 65 and up who are already fully vaccinated." She added that the vaccines "are highly effective and these real-world findings confirm the benefits seen in clinical trials, preventing hospitalizations among those most vulnerable."

Coronavirus cases continue to decline in US

The report comes as the rate of new coronavirus cases has dropped about 16% over the past week in the United States, with the country averaging about 55,000 new cases a day compared to around 66,000 a day last week.

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Over the past two weeks, rates of new coronavirus cases have dropped by at least 15% in 27 states and the District of Columbia, and 14 states have seen drops of over 30%.

As a result, Walensky said she feely "cautiously optimistic that we're turning the corner" in the Covid-19 epidemic, crediting higher rates of vaccination and more people adhering to coronavirus countermeasures.

Surgeon General Vivek Murthy said the drop in cases is "another demonstration of what science has been telling us over the last many months, which is that vaccines are effective in preventing the Covid-19 virus from infecting us."

As of Tuesday, 37.3% of adults in the United States have received a Covid-19 vaccine. According to Anthony Fauci, director of the National Institute of Allergy and Infectious Disease and chief medical advisor to the White House, once vaccination rates hit around 40% to 50%, "I believe you're going to start seeing real change, the start of a precipitous drop in cases."

In early March, after vaccination rates passed 40% in Israel, the country saw a sharp decline in new coronavirus cases, the Wall Street Journal reports.

"At somewhere between 35% and 50% vaccinated, you will see a plateau and then a decline in new cases" in the United States, Eyal Leshem, director of the Center for Travel Medicine and Tropical Diseases at Israel's Sheba Medical Center, said (Anthes, New York Times, 4/28; Fernandez, Axios, 4/28; Bacon/Aspegren, USA Today, 4/28;- Schnell, The Hill, 4/28; Owens, "Vitals," Axios, 4/29; Whelan/Kamp, Wall Street Journal, 4/28; Levin/Qiu, New York Times, 4/28).