COVID-19 Roundup: Vaccines vs. Delta Variant; How the Vital 2nd-Shot Revs Up Immunity; and More

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July 23, 2021


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Study: Pfizer Vaccine Strongly Protects Against Symptomatic COVID from Delta Variant

The vast majority of hospitalizations from COVID-19 are among unvaccinated adults. Meanwhile, growing research shows that the currently available, two-dose mRNA vaccines – from Pfizer-BioNTech and Moderna – provide broad protection against severe illness from the delta variant.

The newest study, published this week in The New England Journal of Medicine, found that the full two doses of the Pfizer-BioNTech vaccine offered strong protection against variants. The research involved more than 19,000 teens and adults across the United Kingdom. When fully vaccinated, with two shots given at least two weeks to take effect, Pfizer’s vaccine became about 88 percent effective against symptomatic COVID-19 from the delta variant.

Researchers said the study’s results nearly reflect the vaccine’s excellent performance in clinical trials leading to its emergency use approval. However, they add that “breakthrough” infections for those vaccinated are more likely with the delta variant — although severe illness is very unlikely. The study stressed that Pfizer’s two shots are necessary for the full protection to take effect against the delta variant.

New research also provides a broader understanding of the delta variant’s mechanism. The latest data finds that it can spread about two to three times faster than the original version of the corona virus. Researchers also have found that the delta variant grows more rapidly inside the infected person’s respiratory tracts and to much higher levels.

The delta variant of COVID-19 is a primary driver behind current surges in infections and hospitalizations across the nation. Most people understand that it’s more contagious and can make those infected who have not been vaccinated more prone to severe illness. Researchers now are seeing how it grows faster in the body after initial infection, compared to other variants or the original strain of COVID-19.

On average, people infected with the delta variant carry about 1,000 times more “copies” of the virus in their respiratory tracts, compared to adults infected with the original strain of COVID-19, according to findings from a study published this month by researchers at China’s Guangdong Provincial Center for Disease Control and Prevention.

Scientists analyzed COVID-19 patients as part of the first outbreak of the delta variant in mainland China, which occurred between May 21 and June 18 in Guangzhou, the capital of Guangdong province. They measured the levels of virus in 62 people, compared them with the levels in 63 patients infected in 2020 with an early version of the coronavirus.

The researchers also found that a person catching the delta variant is likely to become infectious sooner. On average, it took about four days for the delta variant to reach detectable levels, compared with six days for the original strain of the coronavirus.

The delta variant, which first identified in India, is now estimated to make up 83 percent of all sequenced COVID-19 cases in the U.S., a significant jump from 50 percent the week of July 3, the director of the U.S. Centers for Disease Control and Prevention (CDC), Rochelle Walensky, M.D., said this week.


Study: Second Shot of Vaccines Vital to Empower Body’s Immune System Against COVID

The two so-called mRNA vaccines to fight COVID-19 from Pfizer-BioNTech and Moderna require two shots each. New research focuses on the significance of the second dose, especially as the more transmissible delta variant becomes the dominant strain.

The second dose these vaccines produce a substantial boost to a part of the body’s immune system that provides antiviral protection, according to a study led by investigators at the Stanford University School of Medicine and published in the journal Nature.

Researchers urges everyone not to skip that second dose. The researchers examined blood samples from individuals who were vaccinated. They measured antibodies and levels of immune-signaling proteins. Essentially, the vaccines reinforced the body’s T cells and their ability to search tissues with cells bearing certain signs of viral infections. When finding them, this component of the body’s immune system destroys those infected cells.

“The second shot has powerful beneficial effects that far exceed those of the first shot,” said Bali Pulendran, Ph.D., professor of pathology and of microbiology and immunology, in a Stanford University news release. “It stimulated a manifold increase in antibody levels, a terrific T-cell response that was absent after the first shot alone, and a strikingly enhanced innate immune response.”

Unexpectedly, the Stanford researchers said, the vaccines — particularly the second dose — caused the “massive mobilization of a newly discovered group of first-responder cells that are normally scarce and quiescent.”

“The extraordinary increase in the frequency of these cells, just a day following booster immunization, is surprising,” stated Mr. Pulendran. “It’s possible that these cells may be able to mount a holding action against not only SARS-CoV-2 but against other viruses as well.”


Pediatricians Urge Mask-Wearing for All Kids in Schools Older Than 2 — Despite Vaccination Status

The American Academy of Pediatrics (AAP) has updated guidance for schools, recommending that all students over the age of 2 to wear masks, regardless of whether they have been vaccinated against COVID-19. That recommendation also applies to school staff members, the AAP states.

The updated AAP guidance came days after the U.S. Centers for Disease Control and Prevention (CDC) updated its own recommendations, calling for indoor mask-wearing for unvaccinated students ages 2 and up, as well as staff. Children under 12 are not yet eligible for vaccination. The CDC adds that schools might find it necessary to adopt universal mask-wearing in areas with low vaccination rates, or where are is increasing community transmission, or a number of other factors.

In addition to urging everyone who is eligible to get vaccinated, the AAP recommends a “layered approach to make school safe for all students, teachers and staff.” That includes a recommendation that everyone older than age 2 wear masks, regardless of vaccination status. The AAP also echoes the CDC’s recommendations for “building ventilation, testing, quarantining, cleaning and disinfection” in the updated guidance.

“We need to prioritize getting children back into schools alongside their friends and their teachers — and we all play a role in making sure it happens safely,” said Sonja O’Leary, M.D., chair of the AAP Council on School Health. “The pandemic has taken a heartbreaking toll on children, and it’s not just their education that has suffered but their mental, emotional and physical health. Combining layers of protection that include vaccinations, masking and clean hands hygiene will make in-person learning safe and possible for everyone.”

AAP states that universal masking because a significant portion of the student population is not yet eligible for vaccines, and masking is proven to reduce transmission of the virus and to protect those who are not vaccinated. “Many schools will not have a system to monitor vaccine status of students, teachers and staff, and some communities overall have low vaccination uptake where the virus may be circulating more prominently,” the AAP states.

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