Vaccines prevented fewer infections as delta emerged, researchers say

Coronavirus vaccines provided strong protection against infection for essential workers earlier this year, but has become less efficient...

Coronavirus vaccines provided strong protection against infection for essential workers earlier this year, but has become less efficient because the highly contagious Delta variant has become the dominant form of the virus, according to a study released Tuesday by federal health officials.

It was not clear whether the decline in protection was due to the emergence of the Delta variant or the lengthening of the time period since the start of inoculations. The efficacy of the vaccine showed possible signs of decline from four months after the start of vaccinations.

“What we were trying to figure out was, is it Delta, or is this efficiency decreasing? Said Ashley Fowlkes, epidemiologist on the Centers for Disease Control and Prevention’s Covid-19 response team, and lead author of the study. “Our conclusion is that we can’t really tell.”

Researchers followed thousands of first responders, healthcare workers and others who could not work remotely at eight locations in Arizona, Florida, Oregon, Texas, Utah and Minnesota. Participants were tested for coronavirus infection every week for 35 weeks, as well as anytime they developed Covid-like symptoms.

Most of the vaccinated workers received the Pfizer-BioNTech vaccine; a third received the Moderna vaccine and 2% the Johnson & Johnson vaccine.

Overall, vaccines reduced infections among workers vaccinated from Dec. 14, when the U.S. vaccination campaign began, to Aug. 14, by 80 percent, compared to unvaccinated workers. (Results were adjusted for factors such as occupation, demographics, frequency of close social contact, and mask use.)

But while the injections reduced infections by 91% before the emergence of the Delta variant, their protective power dropped to 66% as the variant became dominant in each region.

“We really wanted to let people know that we were seeing a decline in the vaccine’s effectiveness in protecting against any infection, symptomatic or asymptomatic, since the Delta variant became dominant,” said Dr Fowlkes.

“But we also want to reinforce that 66% efficiency is a really high number,” she added. “It’s not 91%, but it’s still a two-thirds reduction in the risk of infection in vaccinated participants.”

The drop in efficacy “should be interpreted with caution”, however, as the observation period in which Delta was dominant was short, Dr Fowlkes said, and the total number of infections was low.

Understanding the mandates of vaccines and masks in the United States

• • Vaccination rules. On August 23, the Food and Drug Administration Granted Full Approval for Pfizer-BioNTech’s Coronavirus Vaccine for people aged 16 and over, paving the way for an increase in terms of office in both the public and private sectors. Private companies have been increasingly compulsory vaccines for employees. Such mandates are legally authorized and have been confirmed in legal challenges.
  • Mask rules. The Centers for Disease Control and Prevention in July advised that all Americans, regardless of their immunization status, wear masks in indoor public places in areas affected by epidemics, a reversal of directions he proposed in May. See where the CDC guidelines would apply, and or states have instituted their own mask policies. The battle over masks has become controversial in some states, with some local leaders defying state bans.
  • College and universities. More than 400 colleges and universities require students to be vaccinated against Covid-19. Almost all are in states that voted for President Biden.
  • Schools. The two California and New York City introduced vaccination mandates for educational staff. A survey released in August found that many American parents of school-aged children are opposed to compulsory vaccines for students, but have been more supportive of mask mandates for students, teachers, and staff who do not have their vaccines.
  • Hospitals and medical centers. Many hospitals and large healthcare systems require their employees to be vaccinated against Covid-19, citing the increase in the number of cases fueled by the Delta variant and stubbornly low vaccination rates in their communities, even among their workforce.
  • New York City. Proof of vaccination is required from workers and customers to indoor dining room, gymnasiums, shows and other indoor situations, although the application does not start until September 13. Teachers and other education workers in the city’s vast school system will have to have at least one dose of vaccine by September 27, with no possibility of weekly testing. City hospital employees also need to get vaccinated or have weekly tests. Similar rules are in place for New York State employees.
  • At the federal level. Pentagon says it will seek to make coronavirus vaccinations mandatory for the country 1.3 million soldiers in active service “at the latest” by mid-September. President Biden announced that all civilian federal employees it should be vaccinated against the coronavirus or submit to regular testing, social distancing, mask requirements, and restrictions on most trips.

Another CDC study released on Tuesday infections analyzed and hospitalizations in Los Angeles County from May 1 to July 25 of this year. Although the vaccinated people were infected, the researchers concluded that among the unvaccinated, the infection rates were 4.9 times higher and the hospitalization rate was 29 times higher.

Of 43,127 known infections in Los Angeles County among residents 16 years of age and older, 25% were in fully vaccinated people, 3.3% in partially vaccinated people, and 71.4% in unvaccinated people. (The proportion of Los Angeles County residents who are fully vaccinated rose to 51% on July 25, from 27% on May 1.)

Three percent of those vaccinated were hospitalized, 0.5 percent were admitted to intensive care units, and 0.2 percent required mechanical ventilation. Comparable rates for unvaccinated people were 7.6%, 1.5% and 0.5%, according to the study.

Those who were hospitalized despite vaccination were also older, on average, than unvaccinated people who were hospitalized. The death rate among the vaccinated was lower: 0.2 percent, compared with 0.6 percent among the unvaccinated. The median age at death was also higher among the vaccinated, at 78 years, compared to a median age of 63 years among the unvaccinated.

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