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While cases of the delta variant surged in Los Angeles County this summer, unvaccinated residents were fives times more likely to get infected and 29 times more likely to get hospitalized with COVID-19 than those who had already been inoculated, a new study from the Centers for Disease Control and Prevention found.

The population-based analysis released Tuesday concluded that fully vaccinated people over the age of 16 who were infected with the virus were less likely than unvaccinated people to be hospitalized, to be admitted to an intensive care unit, to require mechanical ventilation, or to die from COVID infection during a period when the delta variant became predominant.

The study looked at the period from May 1 to July 25, when the delta variant became most prevalent form the virus in the county. During that time, there were more than 43,000 infections in L.A. County residents over the age of 16. Of that total, around 30,800, or 71.4%, were in unvaccinated people, while 10,895, or 25.3%, were in fully vaccinated people and about 1,400, or 3.3%, were in partially vaccinated people.

Exactly one month ago, on July 25, the infection rate among unvaccinated people was 4.9 times the rate among fully vaccinated people, and the hospitalization rate was 29.2 times the rate among fully vaccinated people, the analysis found.

The study also showed fully vaccinated people with the virus were hospitalized at a lower rate, 3.2%, with those admitted to an intensive care unit at 0.5% and those requiring mechanical ventilation at 0.2%. These figures compare with partially vaccinated people at 6.2% hospitalized, 1% admitted to an ICU, and 0.3% requiring mechanical ventilation. And among unvaccinated people, the figures were 7.6% hospitalized, 1.5% in an ICU, and 0.5% requiring mechanical ventilation.

The infection and hospitalization rate data indicates that the authorized COVID-19 vaccines were protective against infection and severe cases during a period with increased community transmission as the delta variant was spreading, the CDC analysis concludes.

“Efforts to increase COVID-19 vaccination, in coordination with other prevention strategies, are critical to preventing COVID-19–related hospitalizations and deaths,” the study states.

In a promising sign that hospitalizations could be leveling off, the county reported only two new patients with COVID-19 Monday following four straight days of declines. But earlier this month, hospitals described unsustainable conditions amid a surge fueled by the delta variant.

As of Monday, there were 1,724 people in the county hospitalized with the virus, along with 2,331 new infections and seven new deaths. The total has reached more than 1.3 million cases to date with 25,078 deaths.