CDC: COVID vaccine effectiveness declines over time

Protection from the COVID-19 virus provided by vaccines declines over time, according to three studies published Wednesday by the Centers for Disease Control and Prevention.

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But while the general effectiveness of the vaccines wane, research shows that the vaccines continue to provide strong protection against hospitalization and death from the coronavirus.

Three articles published in the CDC’s Morbidity and Mortality Weekly Report pointed to the drop in effectiveness against not only the original virus, but also against the delta variant.

“We are concerned that this pattern of decline we are seeing will continue in the months ahead, which could lead to reduced protection against severe disease, hospitalization and death,” Dr. Vivek Murthy, the U.S. surgeon general, said at a White House news briefing on Wednesday.

Members of the Biden administration told The Washington Post that the studies persuaded them to develop a plan to deliver booster shots for those who have been fully vaccinated.

The administration said the shots will be given eight months after a person’s second shot. The boosters will be available beginning on Sept. 20.

The reports posted by the CDC measure vaccine effectiveness. Effectiveness is measured by comparing rates of infection among vaccinated people to rates of infection among unvaccinated people.

One of the three studies was conducted in New York. It found a modest drop in vaccine effectiveness, from 92% in May to 80% in late July.

The second study looked at vaccine effectiveness in nursing homes after the rise in cases of the delta variant. According to the study, vaccine effectiveness dropped from 75% in March through May to 53% in June and July.

In the third study, an analysis of patients at 21 hospitals in 18 states found that the vaccine offered sustained protection against hospitalization. Effectiveness was steady at 86%, according to the study.

In the past 28 days, the United States has seen 2.9 million cases of COVID-19, with 14,483 people dying from the infection, according to Johns Hopkins University of Medicine.

According to the CDC, the delta variant has been identified as the cause in upwards of 90% of all reported COVID-19 cases.