A public health study in the United Kingdom found that protection from the two most commonly used Coronavirus disease Against the current vaccine Delta variant of coronavirus Weakened within three months.
It also found that those who were infected after receiving two injections Pfizer-BioNTech or AstraZeneca Compared with previous variants of the coronavirus, the risk of vaccines to others may be greater.
As the Delta variant spreads in the United States, travelers doubled their COVID-19 vaccination
Based on more than 3 million nose and throat swabs collected in the UK, a study by the University of Oxford found that 90 days after the second injection of Pfizer or AstraZeneca vaccines, their effectiveness in preventing infections dropped to 75% and 61%, respectively.
This is lower than 85% and 68%, respectively, two weeks after the second dose. Compared with people aged 35 and under, the curative effect of people aged 35 and over has decreased significantly.
“These two vaccines are still very effective on Delta in two doses… When you start very very high, you still have a long way to go,” Professor of Medical Statistics and Oxford University Chief Researcher Sarah Walker said. Polls.
Walker was not involved in the work on the AstraZeneca vaccine, which was originally developed by immunologists at Oxford University.
Researchers will not predict how much the protective effect will decrease over time, but the efficacy of the two vaccines proposed to be studied will converge within 4-5 months after the second injection.
Viral load
The study highlights the increased risk of infection with Delta variants, and also shows that despite being fully vaccinated, the viral load of people who are still infected tends to be similar to those of unvaccinated people, which is still dominant with Alpha variants The time has deteriorated significantly in the UK.
The results of the Oxford University study are consistent with the analysis of the Centers for Disease Control and Prevention (CDC). At the same time, the U.S. government has formulated a plan to provide a wide range of COVID-19 vaccine booster injections next month in the case of an increase in Delta variant infections. The data it cited shows that the protective effects of vaccines are diminishing over time.
Israel started taking a third dose of Pfizer last month in response to a surge in local infections caused by Delta. Several European countries are also expected to start providing boosters for the elderly and those with weakened immune systems.
Pfizer has stated that the efficacy of its vaccines will decline over time. AstraZeneca said last month that it is still studying how long the protective effect of its vaccine lasts and whether it needs a booster dose to maintain immunity.
“In fact, we do see…more viral loads suggest that (…) herd immunity may indeed become more challenging,” said co-author Koen Pouwels of Oxford University.
Herd immunity means that a sufficient population is immunized against pathogens through vaccination or previous infections, thereby preventing the increase in the number of infections.
Pouwels said: “Vaccines may best prevent serious diseases, but are slightly worse at preventing transmission.”
The authors warn that the virus concentration in the throat is only a rough indication of the severity of symptoms, and they have no new data on the duration of the infection.
The survey has not been peer-reviewed before being published in a scientific journal, and it highlights scientists’ concerns that the Delta variant first discovered in India can infect fully vaccinated people faster than previous lineages, and vaccinated people It may be easier to spread.
In order to compare the period before and after the Delta epidemic, researchers at the University of Oxford analyzed about 2.58 million swabs taken from 380,000 randomly selected adults between December 1, 2020 and May 16, 2021, and May 810,000 test results from 360,000 participants between 17th and August 16th. 1.
The study was conducted in collaboration with the UK National Bureau of Statistics (ONS) and the Department of Health and Social Care (DHSC).
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