The Pfizer jab has been shown to be 88% effective at preventing Covid-19 infection a month after the second dose. After five to six months, protection decreased to 74%, PA reports.
The AstraZeneca vaccine provides 77% protection against infection one month after the second dose. After four to five months, protection decreased to 67%.
This latest analysis from the Zoe Covid study drew on more than 1.2 million test results and participants. Real-world analysis would be expected to show less protection than clinical trials, and the vaccines were not trialled against the now dominant Delta variant.
Prof Tim Spector, lead scientist on the study, said: “In my opinion, a reasonable worst-case scenario could see protection below 50% for the elderly and healthcare workers by winter.
“If high levels of infection in the UK, driven by loosened social restrictions and a highly transmissible variant, this scenario could mean increased hospitalisations and deaths.”
Earlier, new side effects were detected in Pfizer, Moderna vaccines.