Original title: 1 person infected with Delta variant strain can be transmitted to 5-9 people, experts say there are more reasons to be vaccinated
According to an unpublished document from the US Centers for Disease Control and Prevention cited by foreign media, the Delta mutant virus has a longer transmission window and may worsen the condition of the elderly, even if they have been fully vaccinated.
Specifically, the infectivity of the original strain of the new coronavirus is more similar to that of the common cold. In some cases, the infected person can infect an average of 2-3 people in the initial stage of carrying the virus, but the current Delta mutant strain can infect an average of 5-9 people .
The “breakthrough infection” after vaccination has also raised some people’s questions about the effectiveness of the vaccine. However, experts around the world almost agree that vaccination is still the most effective way to reduce the spread of the virus and can prevent severe illness after infection to a greater extent.
DeltaThe variant strain is as infectious as chickenpox
Earlier this month, the team of Lu Jing, an epidemiologist at the Guangdong Provincial Center for Disease Control and Prevention, published a research article stating that the Delta virus load is about 1,000 times higher than that of the earlier strains.
According to new data released by the US CDC on Friday, about three-quarters of the infected people in Massachusetts have been vaccinated. The new data also found that the nasal swabs of infected people who received two doses of the vaccine carried as much virus as people who had not been vaccinated.
US CDC Director Dr. Rochelle Walensky said in a statement issued on Friday: “The high viral load of the Delta variant indicates an increased risk of transmission and has raised concerns about infections. Those who have been vaccinated with this virus can spread the virus.”
Varensky acknowledged that although the Delta variant is the most serious blow to unvaccinated people, some vaccinated people may carry more viral loads than before and may spread it to other people. This breakthrough transmission behavior is “very different from past virus variants.”
In recent weeks, new data on variants of this highly infectious virus have emerged around the world. The US CDC warned on Thursday that new research shows that the Delta variant is more contagious than swine flu, common cold and polio, and it is almost as infectious as chickenpox. At present, it seems that only measles seems to spread more than the new crown Delta variant. Faster.
In response to the new wave of global epidemics caused by the new crown Delta variant, global experts are further studying the reasons for its rapid spread.
Officials of the World Health Organization said at a press conference on Friday that researchers are still working to understand why the Delta variant is more contagious than the original new coronavirus strain.
Dr. Maria Van Kerkhove, head of WHO’s new crown technology, said: “Possible reasons include certain mutations in the Delta mutant strain that make it easier for the virus to adhere to cells; the more the virus spreads. The faster it is, the better it can adapt to humans. This is the evolution of viruses.”
Vaccines can reduce10More than double the risk of severe death
However, scientists say that even if some of the latest data show that the nasal swab viral loads of vaccinated and unvaccinated infected people are similar, this does not mean that vaccinated people and unvaccinated people have similar viral loads after being infected with the virus. Contagious.
Dr. Monica Gandhi, an infectious disease expert at the University of California, San Francisco, who participated in the study, said: “This is an interesting data. It is very important, but I am not sure if you are vaccinated, your infectiousness will be the same. .”
Gandhi explained that this is mainly due to the multiple components of the immune system, including antibodies and T cells, which has triggered controversy over the use of PCR nucleic acid viral load as the standard for measuring the infectivity of infected persons.
The US CDC research report also stated that the current data have limitations and microbiological studies are needed to confirm these findings, that is, the viral load in “breakthrough infections” is similar. The agency also pointed out: “Asymptomatic breakthrough infections may be underestimated because they are less likely to be detected.”
At present, most studies have shown that the new crown vaccine is still effective for the severe incidence of infection with the Delta variant, although the effect is slightly worse than other new crown variants.
US health officials reiterated this week that about 97% of new hospitalizations and 99.5% of deaths in the United States are unvaccinated people. US CDC internal documents estimate that vaccines can reduce the risk of serious illness or death by more than 10 times, and reduce the risk of infection by about 3 times.
A public health expert told a reporter from China Business News that the rapid spread of the Delta variant has pushed the debate on enhanced vaccines to the forefront.
Pfizer CEO Albert Bourla said at the earnings conference this week that the company and other vaccine manufacturers are accelerating the promotion of the third dose of the new crown booster vaccine, and said that the third dose of booster vaccine will be able to fight Delta variants.
“Pfizer plans to formally submit data on the effectiveness of the third dose of the new crown vaccine to US regulators before mid-August,” he said. Pfizer has raised the company’s 2021 full-year vaccine revenue forecast by 29% to $33.5 billion.
The latest early data released by Pfizer shows that the third dose of virus-neutralizing antibodies produced in young vaccinators is more than 5 times higher than that after two doses, and the neutralizing antibodies produced in elderly people are more than 11 times higher.
The CDC and the World Health Organization in the United States do not yet recommend the use of the new crown booster vaccine, but it is expected that the new crown vaccine developed by Pfizer and Moderna will be fully approved in August this year, and these vaccines are still under emergency authorization.
Dr. Anthony Fauci, a top infectious disease expert in the United States, said that the full approval of the vaccine will help persuade more people to get the vaccine.
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