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Although COVID-19 vaccines are less effective against the Delta variant, they’re still extremely effective in preventing hospitalization, according to data presented Monday to the CDC’s Advisory Committee on Immunization Practices.
Since the Delta variant has become the dominant coronavirus strain, vaccine effectiveness against hospitalization has ranged from 75% to 95%.
In adults over age 75, vaccine effectiveness against hospitalization has dropped slightly but was still above 80% at the end of July. For ages 18-49, efficacy was around 94%.
“Vaccines remain effective in preventing hospitalization and severe disease but might be less effective in preventing infection or milder symptomatic illness,” Sara Oliver, MD, the CDC scientist who presented the information, told the committee.
In a new data analysis released by the CDC on Sunday, unvaccinated adults were 17 times more likely to be hospitalized than vaccinated adults. Hospitalization rates were higher for unvaccinated people in all age groups.
Among the fully vaccinated, people who were hospitalized were much older, more likely to be nursing home residents and more likely to have three or more underlying medical conditions. Nearly a third had immunosuppressive conditions.
Since the Delta variant became dominant, vaccine effectiveness against preventing infection has ranged from 39% to 84%, Oliver said. The drop in efficacy could be linked with the highly contagious nature of the Delta variant and waning vaccine protection over time.
Oliver discussed the idea of booster COVID-19 doses, noting that it’s not uncommon for some vaccines to require multiple doses, such as those for hepatitis and HPV. At the same time, she said, more information is needed before the FDA can provide regulatory clearance and the ACIP can give recommendations for use.
Pfizer has submitted documentation to the FDA for approval of a booster dose, according to CBS News. The data showed that a third shot provided a boost in antibodies between 5 and 8 months after the initial two doses.
The CDC committee will meet again in mid-September to discuss additional data from August as the Biden administration plans to roll out booster after Sept. 20, CBS News reported.
Importantly, Oliver added, those who face the highest risks for severe COVID-19 should receive priority for booster shots. About 1 million Americans have received an additional dose since Aug. 13, when the FDA and CDC cleared some immunocompromised people to get a third shot, CBS News reported.
If booster doses are approved for the general population, she said, the initial shots should go to nursing home residents, healthcare workers, adults over age 75 and frontline essential workers.
In addition, she noted, COVID-19 vaccines should be available to high-risk people worldwide, especially those in low-income countries who haven’t yet received a first dose.
“Uncontrolled spread globally that could result in new variants threaten control of the pandemic everywhere,” she said in the presentation. “Policy around booster doses should also consider equity in the U.S. population.”
CDC: “Framework for booster doses of COVID-19 vaccines, ACIP meeting, August 30, 2021.”
medRxiv: “COVID-19-associated hospitalizations among vaccinated and unvaccinated adults >18 years – COVID-NET, 13 states, January 1 – July 24, 2021.”
CBS News: “COVID-19 vaccine effectiveness in preventing hospitalization drops among oldest Americans, but still over 80%, CDC analysis finds.”
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