Fully vaccinated people who test positive for the Delta variant may be less infectious than those who are unvaccinated and get COVID-19, according to a new study.
Early research led by Erasmus Medical Center in the Netherlands found that fully vaccinated people who caught the more infectious Delta variant cleared the virus more quickly than some unvaccinated individuals who tested positive for the initial COVID strain.
The study, which involved 24,706 health care workers, examined the results of 161 fully vaccinated workers who tested positive for COVID-19 from April to July this year.
Those who test positive after being fully vaccinated are known as “breakthrough cases.”
The breakthrough cases included in the study had all been vaccinated between January and May this year and the majority received either the Moderna or J&J shot. Several received the AstraZeneca vaccine.
Their results were compared to unvaccinated people who tested positive between April and December 2020 — before the Delta variant became prominent.
Researchers say the variant was found in the majority of the cases but the infections were mild and did not require hospitalization.
The study found that fully vaccinated people with the Delta variant were less infectious than unvaccinated individuals who tested positive for the initial COVID strain that is less contagious.
The researchers warned, however, that the infectious virus was found in 68 percent of vaccinated people and the levels decreased in the first three days of illness.
“Despite the reduced viral viability, the infectivity of individuals with breakthrough infections should not be neglected,” the researchers found.
The study concluded that while breakthrough cases are rare, those fully vaccinated individuals were less contagious.
The findings are only preliminary and have not yet been peer reviewed. The study was published publicly on medRxiv, a site that includes preliminary scientific reports.
As the Delta variant continues to spread, the White House said Tuesday it was moving “aggressively” to roll out booster shots this fall for Americans — despite not yet receiving clearance from the Food and Drug Administration to give everyone third doses.
“We are acting aggressively to stay ahead of the virus and are planning for booster shots starting the week of September 20 pending FDA and ACIP [Advisory Committee on Immunization Practices] approval,” Jeff Zients, President Biden’s COVID-19 response coordinator, said at a media briefing.
“We expect the rule will be simple. Get your booster shot eight months after you got your second shot,” Zients said.
To date, the FDA and the Centers for Disease Control and Prevention have only given the green light for booster shots for immunocompromised people who received either the Moderna or Pfizer vaccine.
Johnson & Johnson said Wednesday that its own studies had shown a booster shot for its one-dose vaccine increased antibody levels.