Just one dose of the Pfizer or Oxford-AstraZeneca vaccines significantly reduces the risk of hospitalization for COVID patients in their 80s with preexisting health conditions, a preliminary study shows.
The findings are from AvonCAP, an ongoing surveillance project funded by Pfizer Inc. It gathers detailed information from two National Health Service hospitals in Bristol, Britain, on every adult admitted with symptoms or X-ray evidence of acute respiratory disease.
Researchers identified 434 such patients between Dec. 18 -- 10 days after launch of the Britain's vaccine program -- and Feb. 26. They were eligible for vaccination because they would be at least 80 years old by March 31.
To gauge the effectiveness of single doses of the vaccines, researchers compared immunization rates among adults with acute respiratory disease who tested either positive or negative for COVID-19 when they were admitted to the hospital.
They also accounted for several factors that could affect a person's chances of getting COVID-19 and of being vaccinated, including gender, economic status and living in a care home.
One dose of Pfizer vaccine was 71.4% effective after 14 days at preventing symptomatic illness severe enough to require hospitalization, the study found. Patients' median age was 87, meaning half were older, half younger.
One dose of the Oxford-AstraZeneca vaccine was 80.4% effective after 14 days. Patients' median age was 88, according to findings released March 3.
The Pfizer vaccine has been used in Britain since Dec. 8, and the Oxford-AstraZeneca vaccine has been in circulation since Jan. 4.
When researchers focused on data from early 2021, the effectiveness of a single dose of the two vaccines was nearly identical: Pfizer, 79.3%, and Oxford-AstraZeneca, 80.4%.
The findings are similar to those from other studies in Scotland and England, and have significant implications for countries developing COVID-19 vaccination strategies for vulnerable elderly populations, according to the researchers.
"We are very pleased to share these early results that show the [British] COVID-19 vaccine program is working better than we could have hoped," said chief study investigator Adam Finn, a professor of pediatrics at the University of Bristol.
"We are also delighted our findings could reduce the burden of serious illness in our elderly population and relieve the pressure on the NHS," he added in a university news release. "The AvonCAP study will continue to provide further and more detailed information as time goes on."More information
The U.S. Centers for Disease Control and Prevention has more on COVID-19 vaccines.
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