In a study based on over 1.2 million app users, UK researchers found that the protection offered by two doses of the Pfizer or AstraZeneca covid vaccines began to decline after only 4 to 6 months.
The Pfizer jab is reported to be 88% effective at preventing Covid-19 infection. However, according to the ZOE Covid study, after around 5 to 6 months, this number drops to 74%.
In a reasonable "worst-case scenario", protection could fall to below 50% for the elderly and healthcare workers by winter, analysis from the Zoe #COVID study found https://t.co/9q09t8FNaH
— Sky News (@SkyNews) August 25, 2021
In the case of the AstraZeneca vaccine, after 4 to 5 months, the effectiveness fell from 77% to 67%.
The study was conducted by gathering data from over a million vaccinated app users self-reporting infections, compared with an unvaccinated control group.
Researchers added that it was unclear whether this trend held true for younger people, as younger age cohorts only began to receive their jabs relatively recently compared to the elderly.
“It’s bringing into focus this need for some action,” said ZOE Ltd. co-founder Tim Spector speaking to the BBC.
“We can’t just sit by and see the protectiveness slowly waning whilst cases are still high and the chance of infection still high as well.”
Last week another UK study, this time from Oxford University, found that both the Pfizer and AZ jabs began to lose effectiveness against the Delta variant after as little as three months.
A British public health study has found that protection from either the AstraZeneca or Pfizer-BioNTech vaccines against the now prevalent Delta variant of the coronavirus weakens within three months https://t.co/F3FpBF7DgQ
— Reuters (@Reuters) August 19, 2021
A mere 90 days after the second Pfizer dose, effectiveness against Delta dropped from 85% to 75%, and the AZ jab had dropped from 68% to 61%.