US experts: Delta virus pushes up the threshold of herd immunity to more than 80%
According to the American Society of Infectious Diseases, the Delta variant coronavirus has pushed the threshold for achieving herd immunity to more than 80%, and may even be close to 90%.
At the same time, British researchers said that it may be necessary to develop a new vaccine against the delta strain, because this highly infectious variant virus has already threatened people whose immunity has begun to weaken and may aggravate their symptoms.
The American Society of Infectious Diseases held a briefing on Tuesday (August 3). Assistant Professor Richard Franco of the University of Alabama at Birmingham pointed out at the meeting that the transmission rate of the Delta strain is twice that of the original strain. , The threshold for achieving herd immunity is much higher than the previously estimated 60% to 70%. He said: “This strain is obviously very dangerous, and much more dangerous than the original strain.”
Herd immunity means that most people in the population have developed immunity to a certain disease, which greatly reduces the possibility of the disease spreading from person to person. The World Health Organization had previously estimated that in order to produce herd immunity to the coronavirus, the vaccination rate for the coronavirus must reach about 70%.
According to data from the Centers for Disease Control and Prevention (CDC), as of Monday, 70% of adults in the United States have received a dose of the coronavirus vaccine. This milestone was reached nearly a month later than the goal set by President Biden; nationwide Of the population, nearly 60% have received at least one dose of the vaccine, and about 50% have completed the vaccination.
The White House Coordinator of the Coronavirus Coordinator, Zientz, said at the outbreak briefing on Monday: “There are still about 90 million people in the United States who are eligible but have not yet been vaccinated. We need them to do their best to roll up their sleeves and get the injections. Vaccines. Every shot is important.”
British study: One third of those who have completed the vaccination may still be infected
On the other hand, a large-scale study conducted by experts from various institutions in the UK found that one-third of the people who have completed the vaccination may still be infected. Because the spike protein of the delta strain has mutated to a certain degree, thereby reducing the effectiveness of the antibodies produced by existing vaccines, researchers believe that it may be necessary to develop new vaccines against this strain.
This study of 98,000 people in England showed that the third wave of the outbreak in the UK was caused by the spread of the Delta strain among unvaccinated people, especially young people aged 12 to 24, and some people who had completed the vaccination. of.
Researchers estimate that during the study period, the effectiveness of the vaccine in preventing infection dropped from 64% a month ago to 49%; the protection against symptoms dropped from 83% to 59%.
Recently, with the accelerated spread of Delta strains around the world, the number of “breakthrough infection” cases in some countries is on the increase. “Breakthrough infection” refers to a pathogen that breaks through the vaccine defenses, causing people to remain infected after they are vaccinated. At present, only 13% of the global population has completed the COVID-19 vaccination, and most of them live in developed countries.
However, this study also shows that existing vaccines can still provide relatively high protection, especially after the completion of two injections. If infected, those who have completed the vaccination are less likely to develop symptoms or infect others.