COVID-19 vaccination continues to lag for the youngest children in Mass.

Two-and-a-half-year-old Zachary picked out his Band-Aid before getting his first COVID-19 vaccine in Newton in June.Suzanne Kreiter/Globe Staff

In June, the federal government recommended COVID-19 vaccinations for children aged 6 months through 4 years old, but Massachusetts parents, like their counterparts across the country, have been slow to bring their children in for the shots.

Only 16 percent of children in that age group have had at least one shot, according to the state Department of Public Health. Only 6 percent have been fully vaccinated, meaning they have received either two doses of the Moderna vaccine or three doses of the Pfizer vaccine. Children in the youngest age range are not authorized to receive boosters.

The vaccination rate is much higher among older children. Among 5- to 11-year-olds, 60 percent have had at least one shot, while 52 percent are fully vaccinated. Older adults have reached extremely high rates, with more than 90 percent of those 60 and over fully vaccinated. (The rates have not been as high for booster doses, however, which are recommended for everyone 5 and above.)

Massachusetts’ 16 percent rate of children under 5 receiving at least one dose compares favorably with the national rate of 5 percent, DPH said.

The agency noted that vaccinations for the youngest children were authorized only a few months ago, and emphasized its efforts to encourage the shots, including hosting 480 back-to-school vaccination clinics and working with the state chapter of the American Academy of Pediatrics “and other partners to educate clinicians on ways to increase access to the vaccine and improve pediatric vaccine uptake.”

The Globe reported in August that initial interest in the shots was so weak that pediatricians were being forced to throw away some doses.

Dr. Philip Landrigan, director of Boston College’s Program for Global Public Health and the Common Good, said, “Clearly, we need more children in that age group vaccinated.”

“It’s nice that we’re doing three times better than the national average, but that still means 84 percent of our kids of that age are unprotected,” he said.

“I think the general story out there is that COVID is not a big problem for small children,” said Landrigan, a pediatrician. “While that is true statistically, some do have problems. And if enough get infected, there will be a certain number that have serious infections.”

Other reasons to be vaccinated include preventing children from spreading COVID-19 to vulnerable family members, the dearth of knowledge about the long-term effects of COVID-19 infections on children, and giving children some protection in case a new variant arrives.

“What’s at stake really with this is that we’re going to be setting up a bunch of kids for risk of severe disease in the future,” Dr. Daniel Blatt, a pediatric infectious disease physician at the University of Louisville and Norton Children’s Hospital, told Axios this week. “We don’t really know what the next variant is gonna be. And the way to get ahead of that next variant is to give children a blueprint on how to fight it and that’s what the vaccine does.”

The experts blamed the low participation rate on a variety of factors, including misinformation, inadequate promotion of the vaccines’ benefits, and access issues.

“I think a lot of it has to do with the misinformation that’s been put out there by various parties, encouraging people not to get their children vaccinated or to go slow,” Landrigan said. “The problem is that if parents decide to go slow, then the children are uncovered ... uncovered at a very vulnerable time in their lives.”