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Fully vaccinated people might not be as contagious as you think

Fully vaccinated people who are infected in breakthrough cases might not be as contagious as we thought

Fully vaccinated people who are infected in breakthrough cases might not be as contagious as we thought before.
William and Donna Burroughs, of Nashville, Tenn., go maskless as they cross 200 South at State Street in Salt Lake City on Friday, May 14, 2021. 
Scott G Winterton, Deseret News

A new study suggests that fully vaccinated people might not be as contagious as unvaccinated people infected with the coronavirus.

Do fully vaccinated people spread COVID as much as unvaccinated?

The preprint study — which has not been peer-reviewed but has been published on medrxiv — suggested that fully vaccinated people might not spread the coronavirus as much as unvaccinated people.

Specifically, the study said that “rare vaccine breakthrough infections occur, but infectious virus shedding is reduced in these cases.”

  • The study found that the COVID-19 vaccines are highly effective at stopping death and severe illness, but breakthrough cases do happen (although they remain rare).
  • The researchers studied 161 breakthrough cases out of 24,706 vaccinated people, who were health care workers. They found that there was “lower probability of infectious virus detection in respiratory samples of vaccinated” health care workers compared to unvaccinated health care workers.
  • The study suggested 68.6% of breakthrough cases had infectious virus particles. But the count dropped within three days of illness, a sign that vaccinated people might hold onto the virus for less time than unvaccinated people.

Is the delta variant more contagious?

One minor note with this study — the participants were infected with different variants of the coronavirus. The abstract suggests that the delta variant was identified in the majority of cases. It’s unclear how many other variants were included in the study. But the delta variant has higher transmissibility than other variants, which might impact the results.

Are fully vaccinated people contagious with COVID?

The new study comes days after a separate study from the University of Oxford suggested something contrary — that fully vaccinated people who get infected with the delta variant of COVID-19 can carry the same amount of the coronavirus viral particles as unvaccinated people.

According to CBS News, the researchers from this Oxford study said vaccinated people infected with the delta variant could pose a risk to unvaccinated people because vaccinated people hold so many viral particles.

  • “With delta, infections occurring following two vaccinations had similar peak viral burden to those in unvaccinated individuals,” the study said, per CBS News.

This is why the Centers for Disease Control and Prevention recommended that fully vaccinated people wear face masks again — there was some fear that fully vaccinated people could spread the delta variant to unvaccinated people, which would allow the coronavirus and its variants to spread.

That said, CDC data show that breakthrough COVID-19 cases remain rare among fully vaccinated people. In order to spread the virus, fully vaccinated people would need to be infected by it — which is happening at a rare rate, according to recent data. Some experts have noticed waning COVID-19 vaccine efficacy, though, which is why there has been a call for booster shots.