Protection provided by two doses Pfizer BioNTech and OxfordAstraZeneca New research shows that coronavirus vaccines begin to decrease within six months.
Experts say that under a reasonable worst-case scenario, in winter, the protection rate of the elderly and medical staff may drop below 50%.
One month after the second injection, Pfizer’s vaccine was 88% effective in preventing Covid-19 infection.
However, the latest analysis by Zoe Covid research shows that after five to six months, the protection rate has dropped to 74%, which shows that the protection rate has dropped by 14 percentage points in four months.
AstraZeneca vaccine, One month after the second dose, there is 77% anti-infection protection.
After four to five months, the protection rate dropped to 67%, which indicates that the protection rate dropped by 10 percentage points in three months.
The research draws on more than 1.2 million test results and participants.
More than four months after the second dose, it dropped by 83.7%, and the risk was reduced by 12.5 percentage points.
Real-world analysis is expected to show less protection than clinical trials, and vaccines have not been tested against the currently dominant vaccines. delta A variant of the virus.
Zoe Covid Research launched an app feature in December 2020 to record the Covid-19 vaccine and monitor the actual side effects and effectiveness of its cohort of more than 1 million active users.
Zoe used the vaccine data recorded from December last year to July 2021 and the infection data that occurred between the delta variant dominance in May of this year and July.
The results have been adjusted to give the average risk of infection reduction for the entire population.
The researchers said that although protection appears to be steadily declining, individual risks may vary due to individual differences in antibody duration.
Throughout the UK, the vaccine is being promoted among the oldest and most vulnerable people in society With health workers Before launching the vaccine to young people across the UK.
This means that most people who received the second injection five to six months ago will grow old or be considered vulnerable for other health reasons.
It shows that these people may now be at a higher risk of contracting Covid-19 than those who have been vaccinated recently.
The researchers said that in order to confidently show how the effectiveness of vaccines in different age groups changes over time, more data needs to be obtained over a longer period of time.
Professor Tim Spector, chief scientist of the Zoe Covid Study app, said: “In my opinion, in a reasonable worst-case scenario, the protection rate for the elderly and medical staff may be less than 50% in winter.
“If there is a high infection rate in the UK due to relaxed social restrictions and highly spreading mutations, this situation may mean an increase in hospitalizations and deaths.
“We urgently need to develop a vaccine enhancement plan and, based on vaccine resources, decide whether our strategy for vaccinating children is wise if our goal is to reduce the number of deaths and hospitalizations.
“The weakening of protection is expected. This is not a reason not to be vaccinated.
“The vaccine still provides a high level of protection for most people, especially against the Delta variant, so we still need as many people as possible to get the vaccine.”
