UNITED KINGDOM: The protection provided by two doses of the Pfizer/BioNTech and the Oxford/AstraZeneca COVID-19 vaccines starts to wane within six months of the jab, new research suggests.
The real-world study includes data on positive Covid PCR test results between May and July 2021 among more than a million people who had received two doses of Pfizer or AstraZeneca vaccine.
Conclusion was that protection after two shots of Pfizer decreased from 88% at one month to 74% at five to six months.
At four to five months protection decreased from 77% to 67% for AstraZeneca.
However, it cannot be overlooked that although protection may decrease steadily, individual risk may vary due to individual variation in antibody duration, researchers say.
Professor Tim Spector, lead scientist on the Zoe Covid Study app, said: “In my opinion, a reasonable worst-case scenario could see protection below 50% for the elderly and healthcare workers by winter.”
Across the U.K., vaccines were rolled out first among the older and the most vulnerable in society along with health workers, and later for the younger age groups across the U.K.
This makes the older age group or more vulnerable, the majority to receive their second dose five to six months ago.
This suggests these people are now likely to be at increased risk of COVID-19 compared to those vaccinated more recently.
However, researchers say that in order to confidently illustrate how vaccine effectiveness changes over time in different age groups, more data is needed over a longer period of time.
Despite some breakthrough infections, vaccines are still doing a very good job at protecting people against severe Covid illness and deaths.
Public Health England estimates that around 84,600 deaths and 23 million infections have been prevented as a result of the Covid-19 vaccination programme in England so far.
Prof Spector said: “Waning protection is to be expected and is not a reason to not get 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.”
“We urgently need to make plans for vaccine boosters, and based on vaccine resources, decide if a strategy to vaccinate children is sensible if our aim is to reduce deaths and hospital admissions.”