A University of Birmingham study of elderly recipients found similar immune responses to both the Pfizer and AstraZeneca COVID-19 vaccines. The study’s findings that T-cell levels were lower for those who got the Pfizer shot prompted some social-media speculation about its relative efficacy.
The authors focused on the strong antibody responses five weeks after the initial dose of both shots. “These antibody responses are very encouraging as they back up the strong real-world data we are seeing in the U.K.,” one of its authors said. The study has not yet been peer reviewed.
Another study, with more participants, has corroborated the effectiveness of the Pfizer vaccine in the elderly population, noting that the “the first dose of the Pfizer vaccine was associated with substantially reduced infection risk in residents from four weeks to at least seven weeks.”