Protection against Covid-19 offered by two doses of the Pfizer/BioNTech and the Oxford/AstraZeneca coronavirus vaccines begins to fade within six months, emphasising the need for booster shots, according to researchers in Britain.
After five to six months, the effectiveness of the Pfizer jab at preventing Covid-19 infection in the month after the second dose fell from 88% to 74%, an analysis of data collected in Britain’s ZOE Covid study showed.
For the AstraZeneca vaccine, effectiveness fell from 77% to 67% after four to five months.
The study was based on data from more than 1.2 million test results.
Previous analysis of data has suggested that vaccines protect for at least six months.
Under a worst-case scenario, protection could fall below 50% for older people and healthcare workers by the winter, Tim Spector, principal investigator for the ZOE Covid study, said.
“It’s bringing into focus this need for some action. 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,” Spector told BBC television.
In Greece as the more contagious Delta variant spreads across the country, a leading health expert is now suggesting people layer up or wear double masks to prevent chances of infection.
“The mutation is very aggressive and we need to protect ourselves,” Athina Linou, an epidemiology professor at the University of Athens, told Mega TV on Wednesday.
“Everyone must wear a mask everywhere,” she added.
Laboratory experiments by the US Centers for Disease Control and Prevention (CDC) have shown that well wearing a cloth mask over a three-ply medical procedure mask, as well as knotting the ear loops of a surgical mask and then tucking the excess material close to the face is likely to significantly reduce a person’s exposure to the coronavirus.
On Tuesday, Greece logged a record 4,608 coronavirus cases in one day. What’s more, another 32 deaths were confirmed while 326 patients were intubated.