New research finds vaccines losing effectiveness against getting delta variant but protect against more severe effects

by Alexandra Kelley | Aug. 18, 20921 | Aug. 18, 2021

coronavirus COVID-19 community spread centers for disease control prevention study vaccines booster mmwr cdc delta variant white house

An Emergency Room nurse tends to a patient at the Houston Methodist The Woodlands Hospital on August 18, 2021 in Houston, Texas. Across Houston, hospitals have been forced to treat hundreds of patients in hallways and corridors as their emergency rooms are being overwhelmed due to the sharp increase in Delta variant cases. Brandon Bell/Getty Images

Story at a glance

The U.S. Centers for Disease Control and Prevention issued several studies documenting the waning efficacy of the mRNA COVID-19 vaccines.
Since the vaccines still help reduce severe illness, the White House is looking to roll out a third dose by mid-September.
Full two-dose vaccinations will be required before receiving a third shot.

Following the White House’s new initiative to roll out booster COVID-19 vaccinations in late September, the U.S. Centers for Disease Control and Prevention (CDC) released a slew of data showcasing the current vaccinations’ efficacy in preventing severe illness.

This clinical data is likely one of the factors that informed the decision of White House COVID-19 advisors in recommending booster shots. Notably, the third vaccinations are intended for people who have already been fully vaccinated with a two-series shot from Pfizer or Moderna.

One study conducted by the U.S. Centers for Disease Control and Prevention (CDC) looked at vaccine effectiveness over the course of May 3 to July 25 in New York adults. It found a depletion in overall vaccine effectiveness from 91.7 percent on average to 79.8 percent among all adults surveyed.

The data was sourced from four state databases that stored vaccination information as well as positive and negative COVID-19 test results. Researchers examined new cases and hospitalizations among vaccinated individuals to gauge the quantity of breakthrough infections and their severity.

Ultimately, the study suggested that vaccinated individuals remained out of the hospital more frequently than unvaccinated people, even as the contagious and potent delta variant was circulating.

Rates of new infections did occur, however, which revealed a reduced level of efficacy from the vaccines.

“To reduce new COVID-19 cases and hospitalizations, these findings support the implementation of a layered approach centered on vaccination, as well as other prevention strategies,” the report concludes. A layered vaccination approach would call for booster shots to help regenerate strong immunity levels seen from the first round of vaccinations.

A separate report found smaller rates of declines in vaccine efficacy among the mRNA vaccines. This study looked at 18 states as opposed to just one and saw vaccinated individuals rarely becoming hospitalized.

These findings were consistent for high-risk individuals as well, such as immunocompromised people.

Health experts agreed based on this clinical data and other studies that vaccines, despite exhibiting lower rates of efficacy over time, are still successful in preventing severe infection.

To keep virus-fighting antibody levels high, the booster shot is slated to be available to health care workers and elderly Americans during the week of Sept. 20, pending regulatory approval.