More than one in six toddlers are not getting all of the doses of the recommended early childhood vaccines, according to a new study published in the journal Pediatrics on July 25.

A team of researchers from the University of Montana analyzed vaccination records from 2019 for several childhood immunizations — measles, polio, tetanus, diphtheria, pertussis (whooping cough), Hepatitis B, mumps, rubella, Haemophilus influenzae type b, varicella and pneumococcal infections — for more than 16,300 U.S. toddlers between 19 and 35 months of age.

Most of the vaccines require three or four doses for full protection — but more than 27% of the children had not received the entire series. 

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Nearly 73% of them completed the full series of vaccines, nearly 10% did not start any of the series — and 17.2% started but did not complete one or more of the series, the study said. 

“Increased focus on strategies to encourage multi-dose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals,” the study authors wrote.

The biggest risk factors of vaccine non-compliance included moving across state lines, the number of children in the household and a lack of insurance coverage, according to the study findings in Pediatrics.

Lowered household income, living in a rented home, and race and ethnicity were also factors. 

Black children were more likely to have not completed a full vaccine series than White children, the study found.

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Dr. Shana Johnson, a physical medicine and rehabilitation physician in Scottsdale, Arizona, was not involved in the University of Montana study but reviewed the findings.

“These findings highlight well-known issues in the U.S. health care system, including fragmented care with poor coordination across providers, a complex and difficult insurance system, and unequal access to health care,” she told Fox News Digital.

“Increased focus on strategies to encourage multi-dose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals,” the study authors wrote. (iStock)

On a positive note, Johnson pointed out that 8.4% of the children needed only one additional vaccine dose to complete the series. 

“If the children who were missing only one dose from the vaccine series had received it, the U.S. would have met the Healthy People 2020 goal of 80% coverage for vaccine series completion,” she said.

“This is a worsening from prior CDC statistics of over 90% compliance, which is what you need for herd immunity.” — Dr. Marc Siegel

(The Healthy People 2020 goal was an initiative established by the U.S. Department of Health and Human Services.)

One limitation of the study, noted by the authors, is that the actual reasons behind the missed doses were not collected. 

“The associations provide important insights, but the actual reasons are important data points,” Johnson said.

‘A concerning trend’

Dr. Marc Siegel, professor of medicine at NYU Langone Medical Center and a Fox News medical contributor, also reviewed the study findings and said they mark “a concerning trend.”

“This is occurring especially in socioeconomic disadvantaged areas and involves diseases that are highly contagious and could easily reappear,” Dr. Marc Siegel said. (iStock)

“This is occurring especially in socioeconomic disadvantaged areas and involves diseases that are highly contagious and could easily reappear,” he told Fox News Digital. 

“This is a worsening from prior CDC statistics of over 90% compliance, which is what you need for herd immunity,” he also said. 

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Josh Sharfstein, a pediatrician who is also vice dean of public health at Johns Hopkins in Maryland, told Dr. Siegel last week that he is “very concerned” that the “anti-vaxx movement with COVID” is spilling over to resistance of life-saving childhood vaccines or people not taking them at the right times for full effectiveness.

“I think he is quite right to be concerned,” Siegel said.

Boosting childhood vaccinations

The study authors recommended increasing support for children from low-income families or racial minority groups, who are “most at-risk for infectious diseases and poorer outcomes due to social and environmental determinants of health.”

The study authors recommended increasing support for children from low-income families or racial minority groups. (iStock)

Some suggested aids include greater use of reminder systems, flexible scheduling and pre-visit planning. 

The Centers for Disease Control and Prevention (CDC) also offers a Vaccines For Children (VFC) program, which provides free vaccines to children who may not get immunized due to financial constraints.

“Renewed efforts to better support timely completion of multi-dose vaccine series in early childhood are needed to achieve vaccination coverage goals,” the study authors wrote.