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Are children under 12 more protected from coronavirus if those around them are vaccinated? Experts say yes

Children walked on Arlington Street in Boston last September.John Tlumacki/Globe Staff

As COVID-19 cases rise once again, largely driven by the highly transmissible Delta variant, many are raising alarms about the risk to children who are too young to be vaccinated and likely won’t have access to the vaccine for several months.

But experts say one of the ways to protect kids under 12 is straightforward: Vaccinate the adults around them.

Dr. Kristin Moffitt, a pediatric infectious disease physician at Boston Children’s Hospital, said children under 12 who are not yet eligible for the vaccine become indirectly protected when those around them are vaccinated because kids, especially those who are very young, tend to become infected from adults.

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COVID-19 cases are rising among all age groups in the United States, overwhelmingly among unvaccinated people, meaning infections also are increasing among children.

“Luckily in Massachusetts, we’re not seeing a spike in hospitalizations, and that is a direct reflection of the relatively broad vaccine coverage amongst our populations who are eligible,” Moffitt said. “We are seeing more children testing positive, but not nearly to the extent or at the rate that other parts of the country are seeing.”

Some experts were “a bit shook” to see a report issued by the Centers for Disease Control and Prevention last week on a cluster of COVID-19 cases in Provincetown that demonstrated similar levels of the virus in vaccinated people and unvaccinated people, Moffitt said.

“I think that all certainly gave us pause for worrying about whether or not there’s something different about the Delta variant and how infectious even a vaccinated person might be,” Moffitt said, adding that more data is necessary to determine whether the findings mean vaccinated people are as likely to transmit the virus as unvaccinated people.

The data out of Provincetown represent the detection of viral mRNA — a genetic material — in the swabs from people infected in the cluster, Moffitt said, but not enough is known about “how that correlates with live infectious virus in those individuals and therefore, how likely they were to transmit this infection to others.”

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Data from the CDC show that some states with higher vaccination rates like Vermont — which leads the country in the percentage of its adult population with at least one dose of a vaccine — are seeing fewer infections in children under 12 than states with lower vaccination rates.

States like Tennessee, South Carolina, and Georgia that have relatively low vaccination rates had higher numbers of infections in children between the ages of 5 and 9 per 100,000 people, CDC data show.

In a Twitter thread on Monday night, Dr. Ashish Jha, the dean of the Brown University School of Public Health, argued higher vaccination rates are connected to infections among unvaccinated children by comparing infections in Massachusetts to states with lower vaccination rates, like Louisiana and Florida.

When experts say the United States is now having “a pandemic of the unvaccinated,” that includes kids, but mostly just in communities with lower vaccination rates, Jha wrote.

“Very few kids in highly vaccinated places are getting sick,” he said. “So if you want to protect unvaccinated kids, make sure everyone around them has the shot.”

What’s more, a study conducted in Israel from December 2020 to March 2021 that looked at vaccination records and test results in 177 communities found that vaccination rates are connected to a decline in COVID-19 infections among people under 16, who at the time were unvaccinated.

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“On average, for each 20 percentage points of individuals who are vaccinated in a given population, the positive test fraction for the unvaccinated population decreased approximately twofold,” the study found, leading researchers to believe that vaccinations not only protect those who receive the shots but also unvaccinated people in the community.

Dr. Shira Doron, an infectious disease physician and epidemiologist at Tufts Medical Center, said the Israeli study makes it clear that infections among children are “almost entirely” connected to vaccination rates among adults because mask-wearing was uniform among both groups in the study.

Transmission data show that infections are more likely in private gatherings — not schools or grocery stores — where people are more likely to let their guard down and forgo public health measures like masking or social distancing that help prevent the spread of the virus, Doron said, making it key for adults who live with an unvaccinated child to be vaccinated.

But the Delta variant, which is fueling a rise in cases across the country, is a “game changer,” because it’s more contagious, Doron said.

“When cases are on the rise, they rise in every age group kind of equally,” Doron said. “Vaccinating adults is absolutely the way to protect children in particular, because the under-12s won’t have access to the vaccine until, it looks like, 2022.”

The more transmissible variant changes the threshold to reach herd immunity, Doron said.

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“The increased transmissibility of the virus means that our levels of immunity are not high enough to keep our numbers down,” Doron said. “With that rise, children — and everyone — are less protected equally.”

The COVID-19 vaccine developed by Pfizer-BioNTech is the only vaccine that has been approved for emergency use in the United States for children 12 and older. Moderna and Pfizer launched clinical trials of their vaccines for children under 12 earlier this year, and that data will be submitted to the Food and Drug Administration for approval.

Children are much less likely to get severe COVID-19 than adults and are more likely to be asymptomatic, Doron said. If children do have symptoms, they are more likely to present as a common cold or flu.

Children having greater protection from the virus when they live in an area with higher vaccination rates provides an argument for mandating vaccines in schools — and other places, like businesses and places of employment, Doron said.

“Like hospitals, public schools are places where the children who are there have no choice but to be there,” Doron said. “I think we owe it to them to protect them by being vaccinated. We have to think about how to increase the vaccination of adults in general everywhere, because children come into contact with adults. We’re running up against a wall. We need to be thinking about more drastic ways to increase vaccination of adults everywhere.”

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Amanda Kaufman can be reached at amanda.kaufman@globe.com. Follow her @amandakauf1.