“This rapid rise is disturbing,” she said.

A few weeks ago, delta variants accounted for just over a quarter of new cases in the United States, but now they account for more than 50%-in some places, such as parts of the Midwest, the proportion is as high as 80%.

Researchers from the Institut Pasteur in France reported new evidence on Thursday demonstrating that full vaccination is essential.

In laboratory tests, the blood of the first dose of Pfizer-BioNtech or AstraZeneca-Oxford vaccine from dozens of people “hardly inhibited” the delta variant, the research team Published in the journal NatureBut a few weeks after receiving the second dose of the vaccine, almost everyone received an immune boost that the researchers thought was strong enough to neutralize the delta variant—even if it was slightly less effective than the earlier version of the virus.

French researchers also tested unvaccinated people who survived a coronavirus and found that their antibodies were four times less effective against the new mutant. But the study found that a single dose of the vaccine significantly increased their antibody levels-triggering cross-protection of the delta variant and the other two mutants. This supports the public health recommendation that COVID-19 survivors are vaccinated instead of relying on natural immunity.

Laboratory experiments have added real-world data, showing that mutations in delta variants have not escaped the most widely used vaccines in Western countries, but emphasized that it is crucial to immunize more of the world before the virus evolves further.

For example, researchers in the United Kingdom found that two doses of Pfizer vaccine are 96% protective against hospitalization for delta variants and 88% are effective against symptomatic infections. Canadian researchers responded to this finding last weekend, and an Israeli report indicated that protection against mild delta infections may have dropped to 64%.

Where delta variants are proliferating, whether fully vaccinated people still need to wear masks is a growing problem. In the United States, the CDC insists that fully vaccinated people do not need it. Even before the delta variant, the vaccine was not perfect, but the best evidence shows that if the vaccinated people are still infected with the coronavirus, their cases will be much lighter.

“Let me emphasize that if you are vaccinated, you will get a very high level of protection,” Dr. Anthony Fauci, the top infectious disease expert in the US government, said on Thursday.

Pfizer seeks FDA approval for third booster

Also on Thursday, Pfizer said it plans to seek US approval for its third dose of COVID-19 vaccine.

In general, antibodies will naturally weaken over time, so research is ongoing to determine if and when a COVID booster may be needed.

Pfizer’s Chief Scientific Officer, Dr. Mikael Dolsten, told the Associated Press that early data from the company’s enhanced research showed that people’s antibody levels jumped by 5 to 10 after the third dose compared to the second dose a few months ago. Times.

He said that in August, Pfizer plans to apply to the US Food and Drug Administration for emergency approval of the third dose.

But Dr. William Schaffner, a vaccine expert at Vanderbilt University Medical Center, warned that FDA authorization is only the first step — it does not automatically mean that Americans will get boosters. Public health authorities will have to decide whether they are really needed, especially because millions of people are not vaccinated and still unprotected.

The CDC’s Valensky told reporters on Thursday that in the United States, the case rate has been rising for several weeks, and the hospitalization rate has also begun to rise, which is 7% higher than the previous 7-day average. However, the average death rate is still falling, and some experts believe this is at least partly due to the high vaccination rate among people 65 years and older, who are the most vulnerable to serious diseases.