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Yankees clubhouse a source of ‘breakthrough’ COVID-19 cases. Is that concerning? Here’s what we know

Shortstop Gleyber Torres along with three coaches and four support staff were among those who tested positive for the virus.
Shortstop Gleyber Torres along with three coaches and four support staff were among those who tested positive for the virus.Tony Dejak/AP/file

Eight members of the New York Yankees tested positive for COVID-19 this week, despite being fully-vaccinated against the virus — an occurrence known as “breakthrough” positive cases.

Shortstop Gleyber Torres along with three coaches and four support staff were among those who tested positive for the virus as of Thursday. All eight had received Johnson & Johnson’s single-dose shot, according to manager Aaron Boone, and Torres had previously contracted the virus during the offseason, according to prior reports.

At least 85 percent of the team had been vaccinated as of April 30, which qualified the clubhouse to ease up on its mask-wearing protocols under MLB rules, meaning the team no longer had to wear masks in dugouts and bullpens. Restrictions during road trips were also loosened.

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The news of the team’s eighth breakthrough case came on the same day the CDC announced that fully vaccinated Americans no longer have to wear masks indoors or outdoors in most cases. A person is considered fully vaccinated two weeks after receiving the Johnson & Johnson single-dose, or two weeks after receiving the second dose of the Pfizer or Moderna two-shot vaccine, according to the CDC.

“With regard to the Yankees, we obviously need to learn more about that situation,” CDC director Dr. Rochelle Walensky said at a news conference.

Vaccine breakthrough cases can occur in “only a small percentage” of vaccinated people, according to the CDC. The breakthroughs demonstrate that while shots are effective, they are not 100 percent foolproof in preventing illness.

“Even though a small percentage of fully vaccinated people will get sick, vaccination will protect most people from getting sick,” the CDC website says. “There also is some evidence that vaccination may make illness less severe in people who get vaccinated but still get sick. Despite this, some fully vaccinated people will still be hospitalized and die.”

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It was reported that seven out of the eight cases within the organization were asymptomatic, which, according to the CDC, means the vaccine is doing what it’s supposed to. By Thursday, all of the cases were asymptomatic, according to general manager Brian Cashman.

In clinical trials, the Johnson & Johnson vaccine was found to cut the risk of infection by 66 percent globally and by 72 percent in the US. The trial also found that the J&J shot reduced the risk of severe disease by 85 percent. By comparison, the Pfizer and Moderna two-shot vaccines prevented 95 percent and 94.1 percent of symptomatic cases, respectively.

Looking at those numbers, it may be tempting to suggest the Johnson & Johnson vaccine might have the highest risk of breakthrough cases, but infectious infectious disease expert Amesh Adalja told Health.com “you can’t compare efficacy numbers like that, because the vaccines were not studied head to head, at the same time, or with the same prevalence of variants,” he said.

The CDC also said a person could become infected just before or just after they’ve been vaccinated and still get sick. Variants of the virus could also be a reason for the positive tests, an infectious disease specialist told the Washington Post.

“The vaccines do appear to be a little bit less effective against some of these variants, specifically ones that have mutations,” virologist and research scientist Angela Rasmussen told the Post. “Depending on what variant they were infected with, that also might have something to do with the breakthrough infections that were seen on the Yankees.”

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As of April 26, the CDC had received around 9,200 reports of breakthrough infectious out of more than 95 million people who’d been fully vaccinated at that point. Around 27 percent of those cases were asymptomatic, and 1 percent of those people had died.

Beginning on Friday, though, the CDC said it would change the way it reported breakthrough infections to only include those who were hospitalized or died. The Yankees’ cases, under this new standard, wouldn’t qualify as breakthrough infections going forward.


Brittany Bowker can be reached at brittany.bowker@globe.com. Follower her on Twitter @brittbowker.