Just one dose of the Pfizer or Oxford-AstraZeneca vaccines significantly reduces the risk of hospitalization for coronavirus disease 2019 (Covid-19) patients in their 80s with preexisting health conditions, a preliminary study showed.
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 December 18 – 10 days after launch of the Britain’s vaccine program – and February 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 percent 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-percent effective after 14 days. Patients’ median age was 88, according to findings released March 3.
The Pfizer vaccine has been used in Britain since December 8, and the Oxford-AstraZeneca vaccine has been in circulation since January 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 percent, and Oxford-AstraZeneca, 80.4 percent. SOVEREIGNPH