The Centers for Disease Control and Prevention (CDC) released new data on Wednesday Aug. 18, warning of a “significant decline” in vaccine effectiveness against COVID-19 infection in nursing home residents, as the virus’s highly contagious Delta variant causes an increase in hospitalizations among Americans.

The announcement came as the Biden administration announced that effective Sept. 20, all Americans who received the Pfizer or Moderna vaccinations will be eligible for booster injections eight months after their second dosage.

The CDC stated that the existing approved vaccinations remain extremely effective against COVID-19 hospitalization, which means that even if someone becomes infected after being vaccinated, they are unlikely to become very ill.

“The data we will publish today and next week demonstrate the vaccine effectiveness against SARS CoV-2 infection is waning,” CDC Director Rochelle Walensky said at a press conference. “And even though our vaccines are currently working well to prevent hospitalizations, we are seeing concerning evidence of waning vaccine effectiveness over time, and against the delta variant.”

All three investigations compared the rates of illness or hospitalization among vaccinated persons against the rates among unvaccinated people to determine vaccination efficacy.

However, the CDC investigations were unable to determine whether the decrease in infection efficiency was due to the delta variation, changes in people’s behaviour, and the relaxation of masking and distance requirements, or a genuine decline in immunity.

The data from the three investigations, which were published in the CDC’s Morbidity and Mortality Weekly Report on Wednesday, helped persuade the Biden administration that booster injections should be given to patients eight months after their second dosage.

Boosters will begin being administered on Sept. 20 under the plan announced Wednesday, pending FDA approval of a third dose and a meeting of the CDC advisory committee to make evidence-based recommendations.

“We are concerned that this pattern of decline we are seeing will continue in the months ahead, which could lead to reduced protection against severe disease hospitalization and death,” stated Surgeon General Vivek Murthy.

The CDC statistics, according to health experts, should make the point that getting first doses to the unvaccinated and boosters to immunocompromised ones and nursing home residents, rather than the whole population, is more essential.

“I mostly care about hospitalizations, I don’t care about infections because this is not what we’re using vaccines for. We’re not trying to stop infections, and there’s no evidence that a third booster will stop infections” Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Center for Health Security and a senior scholar, said.

From May 3 to July 25, research looked at the vaccinated and unvaccinated in New York. The total age-adjusted efficacy against new COVID-19 cases for all adults fell from 91.7% to 79.8%, according to the research.

During the same time span, hospitalization effectiveness remained pretty steady, ranging from 91.9% to 95.3%.

According to Nuzzo, such figures don’t support giving a third dosage, especially because a second research indicated that the vaccinations were still 90% effective in preventing hospitalizations.

“What could be perceived as the vaccine not protecting as much as it did before based on time could just be due to the fact that we’re challenging the vaccine more than we did before,” Nuzzo explained.

She then added: “We need to remember that vaccines aren’t force fields—they don’t prevent infections. They train your immune system to respond quickly to infections and hopefully limit the number of cells that get infected. They work to limit infections to prevent severe disease, hopefully to keep people out of the hospital.”

According to the study, vaccinations alone will not be sufficient to minimize new COVID-19 cases and hospitalizations. The findings point to a multi-pronged approach that involves vaccinations as well as other preventative methods including masking and physical separation.

Nursing home residents, who are frequently elderly and fragile and may have a less strong reaction to vaccinations, might benefit from boosters.

According to a third CDC research, vaccination efficacy in nursing homes has dropped considerably in recent months.

The study looked at vaccination efficacy in roughly 4,000 nursing home patients from March 1 to May 9, before the Delta variation appeared, and nearly 15,000 nursing home residents from June 21 to Aug. 1, when Delta was the predominant variant generating new illnesses across the country.

During the era of Delta variant circulation, the efficacy fell from around 75% to 53%.

“It makes sense to give an extra dose of vaccine to vaccinated nursing home residents, but what will have an even bigger impact on protecting those nursing home residents is to vaccinate their caregivers,” Celine Gounder, an infectious diseases doctor at Bellevue Hospital Center and former COVID-19 adviser to the Biden campaign, tweeted.

The CDC researchers were unable to identify whether the decline in efficacy was due only to the Delta variation or a mix of Delta and decreasing immunity. The vaccinations’ protection against severe illness was also not assessed in the research.

Global health experts have urged “rich countries” to postpone booster vaccinations until at least the end of next month, in order “to enable at least 10% of the population of every country to be vaccinated.”

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