COVID-19 Vaccine Effectiveness Dropping as Number of ‘Breakthrough’ Infections Rise: Studies

People walk past a sign for a COVID-19 vaccination clinic in Los Angeles, Calif., on Aug. 17, 2021. Lucy Nicholson/Reuters

COVID-19 vaccines are declining in effectiveness against infection protection as the number of so-called “breakthrough” infections rise, according to two studies published Tuesday.

COVID-19 is the disease caused by the CCP (Chinese Communist Party) virus.

Participants in an ongoing study called HEROES-Recover, which has cohorts across the United States, initially enjoyed strong protection after getting vaccinated against infection from the virus, according to one of the studies.

But the efficacy of COVID-19 vaccines dropped from 91 percent before the Delta variant became dominant in the United States to 66 percent afterward, researchers said.

They drew from infection data for five cohorts, including workers in Arizona, Duluth, Minnesota, and Portland, Oregon.

The decline in effectiveness matches that seen in a slew of other studies, though researchers cautioned against reading too much into it.

“This trend should be interpreted with caution because [vaccine efficacy] might also be declining as time since vaccination increases and because of poor precision in estimates due to limited number of weeks of observation and few infections among participants,” the researchers, including Ashley Fowlkes of the Centers for Disease Control and Prevention (CDC) COVID Response Team, wrote.

They followed 4,136 participants for 35 weeks starting in December 2020 through the cohorts.

Similar studies published recently show waning effectiveness for vaccines, including one from the Mayo Clinic and another from scientists in the United Kingdom.

In another study published by the CDC on Tuesday, the number of so-called breakthrough infections, or CCP virus infections among the fully vaccinated, grew to 25 percent of all infections in Los Angeles County between May 1 and July 25.

Another 3 percent were in people who had received a single dose of the two-dose Moderna or Pfizer regimen. They’re known as partially vaccinated.

The rest were in the unvaccinated. The percentage of unvaccinated who were previously infected were not noted.

Researchers analyzed more than 43,000 reported infections among people aged 16 or older.

A nurse prepares a Pfizer BioNTech COVID-19 vaccination as part of a vaccine drive by the Fernandeno Tataviam Band of Mission Indians in Arleta, Los Angeles, Calif., on Aug. 23, 2021. Lucy Nicholson/Reuters

They found 350 fully vaccinated LA County residents were hospitalized, along with 89 partially vaccinated residents.

In addition, 24 fully vaccinated persons and 7 partially vaccinated persons died.

But those numbers were eclipsed by the unvaccinated, with 2,355 people who haven’t gotten a vaccine needing hospital care and 176 dying.

On July 25, infection and hospitalization rates among unvaccinated persons were 4.9 and 29.2 times, respectively, those in fully vaccinated persons, the Los Angeles County researchers said.

“The results of this population-based analysis using linked SARS-CoV-2 infection surveillance and vaccination registry data indicate that fully vaccinated persons aged ≥16 years with SARS-CoV-2 infection were less likely than unvaccinated persons to be hospitalized, to be admitted to an intensive care unit, to require mechanical ventilation, or to die from SARS-CoV-2 infection during a period when the Delta variant became predominant,” they wrote.

SARS-CoV-2 is another name for the CCP virus.

Waning effectiveness of the COVID-19 vaccines recently led to officials announcing publicly that they are ready to recommend all adults, including the healthy, get a booster shot starting in September, pending Food and Drug Administration approval.

But officials have emphasized that the vaccines appear to be holding up well against hospitalization and severe disease, and are still encouraging practically everybody to get a jab.