Study: 1 in 6 US children have received vaccine dose at incorrect time

BySara Kellner

Fact checked byCarol L. DiBerardino, MLA, ELS

Key takeaways:

Over a 10-year study period, 15.4% of children received at least one vaccine dose at an incorrect time, such as being too young.
The rotavirus three-dose vaccine was the most common series with invalid doses.

Nearly one in six U.S. children received at least one vaccine dose outside the recommended age guidelines during a recent 10-year period, according to study findings published in Pediatrics.

“Vaccine age and timing recommendations exist to promote effective stimulation of the immune system for optimal protection,” Alexandria N. Albers, MPH, MS, a graduate research assistant at University of Montana, told Healio. “Vaccines given outside of age guidelines can raise concerns about inadequate disease protection or safety in some situations of invalid doses.”

Albers and colleagues studied data from the 2011-2020 National Immunization Survey-Child, a phone survey that asks parents about their child’s vaccine history from age 19 to 35 months, to see how prevalent invalid vaccine doses were and whether children who received invalid doses completed the series later.

Because response rates in 2018 to 2020 were significantly lower than in 2011 to 2017 — a result of switching from calling landlines and cell phones to cell phones only — the researchers reported weighted percentages in the study.

Over the study period, children aged 19 to 35 months were recommended to receive four doses of DTaP and pneumococcal conjugate vaccine; three or four doses for Haemophilus influenzae type b (Hib) depending on the vaccine; three doses for hepatitis B virus and polio; two or three doses of rotavirus vaccine depending on the shot; two doses for hepatitis A virus and seasonal influenza; and the first dose of the MMR and varicella vaccines. The rotavirus vaccine is the only one with a maximum age, as children are recommended to receive the first dose before age 15 weeks and the last dose before age 8 months, according to the CDC.

Too young, too soon, too old

Out of 161,187 children, 15.4% had at least one invalid vaccine dose over the 10-year study period (95% CI, 15%-15.8%), the researchers reported. The most common vaccines with invalid doses were for rotavirus (4.4%; 95% CI, 4.2%-4.6%), Hib (3.3%; 95% CI, 3.1%-3.5%), HAV (2.3%; 95% CI, 2.2%-2.5%) and HBV (2.1%; 95% CI, 1.9%-2.2%).

“These invalid doses were either given at too young of an age, too soon relative to a prior dose of the same vaccine, or in the case of rotavirus vaccination, given at too old of an age,” Albers said.

The CDC’s Advisory Committee on Immunization Practices recommends children receive a repeated dose of any vaccine that was administered too early to complete the series, according to Albers and colleagues, but only 44.9% (95% CI, 43.2%-46.6%) did so. The proportion of children with invalid doses who completed their vaccine series increased from 29.5% in 2011 to 52.9% in 2020.

Out of 1,557 children who received their first dose of MMR between ages 6 and 11 months — earlier than is recommended — the researchers reported that 75.6% (95% CI, 71.2%-80%) received a repeat dose after the recommended age of 12 months.

“An unexpected and positive finding was that the number of children receiving vaccines outside of age guidelines decreased over the 10-year period we examined,” Albers said, referring to a decline from 16.9% of children in 2011 to 12.5% in 2020.

Children who had three or more providers were 50% more likely to have invalid doses compared with children with one provider (adjusted OR = 1.5; 95% CI, 1.2-1.8), and children who moved between states were also more likely to have invalid doses than those who did not (aOR = 1.5; 95% CI, 1.4-1.6). Receiving vaccines from a hospital-owned clinic reduced children’s odds of invalid doses compared with private clinics (aOR = 0.8; 95% CI, 0.7-0.9).

‘Only one chance to get it right’

“Albers and colleagues’ well-executed study demonstrates that process, product and patient factors are all at play when it comes to vaccine timeliness,” David G. Bundy, MD, MPH, professor of pediatrics at the Medical University of South Carolina, wrote in a related editorial.

He pointed out that the variation in dosing schedules for different products targeting the same diseases can be confusing for providers. For example, the three-dose rotavirus vaccine, which was the most common culprit for invalid doses, gives providers “only one chance to ‘get it right,’” because of how the minimum ages, maximum ages and intervals between doses line up with routine well-child visits, he wrote. However, the two-dose rotavirus vaccine was the least common series to have invalid doses because it provides more flexibility for administering the second dose.

Albers said the next steps in this research will be looking for strategies to reduce vaccine administration errors and educating providers about resources that are available.

“An important takeaway for all vaccination providers is that there is health technology called Clinical Decision Support for Immunizations to help them recommend the right vaccines at the right ages,” Albers said. “This technology should be used in all settings where children get vaccines.”