Unvaccinated people were 11 times more likely to die from COVID-19 compared to those who were fully vaccinated, the Centers for Disease Control and Prevention reported in a new study Friday, providing more evidence of the vaccines’ effectiveness at preventing severe disease, even as protection from mild breakthrough cases appears to be waning in the face of the Delta variant.
“Looking at cases over the past two months when the Delta variant was the predominant variant circulating in this country, those who were unvaccinated were about four and a half times more likely to get COVID-19, over 10 times more likely to be hospitalized, and 11 times more likely to die from the disease,” CDC Director Rochelle Walensky said at a briefing Friday.
The CDC’s latest data, published as three studies Friday in the agency’s Morbidity and Mortality Weekly Report, are also the latest sign that booster shots could become necessary in the coming months for many.
Examining the incidence of COVID-19 across 13 jurisdictions in the United States, the CDC reported that the odds of fully vaccinated people becoming sick with the virus rose as the Delta variant surged across the country.
Scientists expected fully vaccinated people to make up some 10% of cases from late June through July, if the shots retained peak effectiveness at preventing any infection. Instead, vaccinated persons accounted for 18% of observed cases — a finding the study’s authors said “were consistent with a potential decline in vaccine protection against confirmed SARS-CoV-2 infection.”
However, while protection against hospitalization and death remained relatively high in the study through mid-July, the CDC also published new data showing further evidence of waning protection against severe disease in the oldest Americans.
In data collected from the agency’s “VISION Network” cohort of hundreds of hospitals and urgent care clinics, the agency reported that vaccine effectiveness against hospitalization in adults 75 and older “was significantly lower” than in younger patients through August. A handful of Veterans Affairs Medical Centers reached a similar conclusion in their data, estimating effectiveness against hospitalization for adults 65 and older at 80%.
Both studies reported that their findings of declining effectiveness against hospitalization had not been previously observed in their cohorts.
The CDC has previously reported vaccine effectiveness against hospitalization appearing to drop over time in other cohorts, though still remaining above 80% through July.
The new results come as federal health officials say they are moving ahead with plans to roll out booster shots nationwide, pending approval from the Food and Drug Administration and formal recommendations from a panel of the CDC’s expert vaccine advisers.
Pfizer is expected to be first to win approval from the FDA for a booster shot. The regulator plans to convene its panel of vaccine experts to deliberate over the company’s booster shot data next week, ahead of the administration’s planned rollout the week of September 20th.
Federal health officials say they also hope to allow for booster shots for recipients of Moderna and Johnson & Johnson’s vaccines in the coming weeks, pending more data from the drugmakers.
The Biden administration has also pointed to data collected abroad to underscore the need to roll out additional doses of the vaccine for those most at-risk; Israel, for example, has already begun administering booster shots.
“Israel has been a very interesting phenomenon to observe, because they seem to be ahead, certainly of the United States, in every element of the outbreak, including response to vaccines,” Dr. Anthony Fauci, the president’s chief medical adviser, told a virtual event hosted by the London School of Hygiene and Tropical Medicine on Wednesday.
Yale University researchers, in a federally-funded preprint study that has yet to be peer-reviewed, recently reported the early booster shot rollout there appeared to reduce the odds of an infection by up to 68%.
Israeli health officials have also briefed the Biden administration on additional unpublished data from their booster program. The country’s prime minister recently urged President Biden to speed the U.S. booster strategy, which currently plans for Americans to get their additional shots 8 months after completing their initial regimen.
“Although earlier studies showed that hospitalization protection, most recent studies, in my personal communication with Israeli health authorities, indicate that there’s even now a significant diminution,” added Fauci.