As the Delta variant became dominant in the U.S. this summer, data showed that unvaccinated Americans were 4.6 times as likely to be infected, 10 times as likely to be hospitalized and 11 times as likely to die from Covid-19 than vaccinated people.
In a trio of studies released Friday underscoring the effectiveness of Covid-19 vaccines even against the highly contagious Delta variant, the Centers for Disease Control and Prevention examined Covid-19 outcomes among patients who visited emergency departments, urgent care centers and veterans’ hospitals.
One study that tracked patients at five Veterans Affairs Medical Centers across the country between Feb. 1 and Aug. 6 found that mRNA vaccines were 87% effective at preventing Covid-19 associated hospitalization, including during the Delta surge. The study found that effectiveness dropped to 80% for patients over the age of 65, while for younger patients, the vaccines were 95% effective.
Another study, which examined more than 600,000 cases in 13 states and large cities, examined two time periods in the spring and summer and found a slight decline in vaccine effectiveness during the period when Delta became the dominant strain in the U.S., starting around mid-June.
Before Delta became the most widespread variant, it was causing 16 times as many deaths a week, on average, among the unvaccinated as among the vaccinated, the study found. After Delta took hold, that ratio fell to 11 times as many deaths.
The rate of weekly hospitalizations and cases notched similar declines between the pre-Delta and post-Delta periods, but the difference in outcomes between vaccinated and unvaccinated people remained stark. The unvaccinated were 4.6 times as likely to become infected as the vaccinated, and 10 times as likely to go to the hospital for Covid-19.
“We are seeing more people in the hospital who have been vaccinated, but I want to reiterate that it’s still well over 90% of the people who are in the hospital who are unvaccinated,” CDC Director Rochelle Walensky said at a news briefing.
A third study, which examined the experiences of nearly 33,000 patients who visited hospitals, urgent care centers and emergency departments in nine states for Covid-19, found that the vaccines’ protection against hospitalization was around 86% through the Delta period, similar to the months preceding Delta’s dominance, although vaccine effectiveness did wane among patients over the age of 75.
Federal officials said the reports bolstered conclusions from earlier research that vaccines are the most effective tool against Covid-19 and the fastest way to bring the pandemic to heel.
“The most important thing we can do to protect against any variant is vaccinate,” said Anthony Fauci, the top U.S. infectious disease specialist.
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