A cocoon of vaccination provides ‘substantial’ protection for unvaccinated kids, studies find

When parents ask pediatric infectious disease specialist Dr. Amy Edwards how they can keep their littlest ones safe from Covid-19, she says it’s simple.

“Get everyone around them vaccinated, and that will protect your kid pretty well,” said Edwards, who is the associate medical director, pediatric infection control at UH Rainbow Babies and Children’s Hospital in Cleveland. “It’s not complete protection, but it is better protection.”

Parents pick up their children from Hawthorne Scholastic Academy following their first day of in-person learning on March 01, 2021 in Chicago, Illinois. Students in kindergarten through fifth grade began in-person learning today as the city continues to phase in a return to the classroom after nearly a year's hiatus and a lengthy battle with the teacher's union brought on by COVID-19 concerns.

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New Covid-19 cases among children in the US topped 1 million last week for the first time since the American Academy of Pediatrics began tracking cases, the group said Tuesday, and the numbers are now nearly five times the rate of the peak of last winter’s surge. But kids under age 5 are still not eligible for Covid-19 vaccines in the United States.

However, there’s new evidence that they can get significant protection from the coronavirus if everyone around them is vaccinated.

Two new studies done in Israel found that vaccinating people in a household reduces the transmission of the virus that causes Covid-19. The studies were published Thursday in the journal Science.

One study looked at the time between January and March 2021, when the Alpha coronavirus variant was in wide circulation, and between July and September 2021, when the Delta variant had taken over in Israel. During the first period, no children in Israel were eligible to get the vaccine. By the second time period, only children 12 years and older were eligible.

Researchers found that kids who lived in a household with a single vaccinated parent had a 26% lower risk of catching Covid-19 at the start of 2021. Having a vaccinated parent was still protective when the Delta variant was in wide circulation, but the decreased risk fell to 20.8%.

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If the child lived in a home where two parents were vaccinated, they had a significantly reduced risk of catching Covid-19. During the part of the pandemic when the Alpha variant was in circulation, kids with two vaccinated parents had a 71.7% reduced risk. With Delta, it was a 58.1% decreased risk.

“Parental vaccination confers substantial protection for unvaccinated children in the household,” said the researchers, who worked at Harvard University, Clalit Research Institute, Ben Gurion University, Tel Aviv University and Boston Children’s Hospital.

Another study looked at the rate of transmission among household contacts and bolstered the case for indirect protection from vaccines.

The researchers found that before the Delta variant, people who got the Pfizer/BioNTech vaccine and got breakthrough cases had slightly reduced infectiousness compared with those who got sick and were not vaccinated.

Researchers at Yale University and the Maccabi Institute for Research and Innovation looked at households that had been vaccinated with the Pfizer vaccine before and after the Delta variant was in wide circulation.

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The total vaccine effectiveness was estimated to be 91.8% within 10 to 90 days after vaccination and 61.1% more than three months after the second dose. There was evidence that protection waned beyond that time period, and the study did not take boosters into account.

When the Delta variant became dominant, the effectiveness of the Pfizer vaccine dropped to 65.6% within 10 to 90 days and 24.2% more than three months after the second dose.

But even with the decline in effectiveness, when researchers looked at the risk to children in these households, they found a “larger reduction in risk for children exposed to a vaccinated versus unvaccinated infectious household member regardless what variant was in circulation,” the study said.

The household is where many cases begin, the study suggests. Other studies have suggested the same. The risk of transmission from an infectious household member was 100 times as high as that of the average risk of infection from the community.

There was no meaningful increase in household transmission when Delta was in circulation. Children, though, had a lower risk of infection from both the community and an infectious household member, and ill children themselves were slightly less infectious than adults.

“We’ve always known that kids are not the primary transmitters of this virus,” said Edwards, who was not affiliated with the new studies. “Adults have always been the primary transmitters of this virus, and so that’s why it’s always been incumbent on us, as adults, to be the ones to get vaccinated and to be the ones to wear the masks and to be the ones to be careful, because we’re the ones that are primarily driving these outbreaks. We are the ones that can keep them safe.”