COVID infections protecting is waning in double-jabbed people, reported BBC quoting researchers. In UK, experts conducted a real-world study of positive COVID PCR test results between May and July 2021 among more than a million people. These people had received two doses of Pfizer or AstraZeneca vaccine.
Protection of people who were administered Pfizer's COVID vaccine decreased from 88% at one month to 74% at five to six months. For AstraZeneca, the fall was from 77% to 67% at four to five months.
Experts said that there are chances of breakthrough infections, but vaccines are still saving people's lives from COVID.
According to Public Health England, around 84,600 deaths and 23 million infections have been prevented as a result of the vaccination programme in England so far.
Prof Tim Spector, who is the lead investigator on the Zoe COVID Study app behind the research, said the findings could explain recent breakthrough infections in fully vaccinated people.
He added waning is to expected and people should still vaccinated. "Vaccines still provide high levels of protection for the majority of the population, especially against the Delta variant, so we still need as many people as possible to get fully vaccinated," said the researcher.
According to Spector, the protection could drop to 50% by the winter and boosters will be needed, but other experts urge caution about making predictions for the months ahead.
From September, the UK is expected to offer a third COVID booster jab to some people and is waiting for recommendations from an independent advisory body called the JCVI.
Dr Simon Clarke, an expert in cellular microbiology at the University of Reading, said it is hard to draw firm conclusions about waning immunity as infection levels in the community would alter a person's chance of encountering and catching COVID at any given time.
It was important to understand that who needs booster doses and at what time, said Dr Alexander Edwards, also from the University of Reading.
Office for National Statistics and the Oxford Vaccine Group also published a similar study last week.
The study was based on PCR test results of nearly 400,000 people, who had been infected with the Delta variant in the UK. The study revealed that two doses of the Pfizer vaccine was initially more than 90% effective against symptomatic COVID infection, compared to around 70% for the AstraZeneca vaccine.
The protection from Pfizer fell over the course of three months, whereas immunity with the AstraZeneca jab remained more stable.