For several years, the COVID-19 pandemic disrupted routine childhood vaccinations across the U.S., reducing the number of children entering kindergarten vaccinated against serious, highly contagious diseases such as the measles, diphtheria and polio, an analysis from the U.S. Centers for Disease Control and Prevention found.
The vast majority of America’s approximately 4 million kindergarteners start school fully vaccinated, meaning they have received all doses of the vaccines their state requires. But the proportion dipped from 95% during the 2019-20 academic year to about 93% in 2022-23, the most recent year for which data was available, the CDC reports.
As childhood vaccination rates have dropped, outbreaks of measles — declared eliminated in the U.S. in 2000 — have increased. So far this year, 211 measles cases and 13 outbreaks were reported in the U.S., up from 59 cases and four outbreaks during all of 2023, according to the CDC.
In the coming months, education and public health leaders will likely discuss vaccination rates and ways to reverse the trend both nationally and in local communities. As schools prepare for the fall semester, administrators are checking children’s shot records and working with families to help kids get up to date.
Researchers have spent decades studying strategies that encourage people to get vaccinated. Public health officials warn that communities do not have herd immunity against a disease until a high percentage of people become immune to it, usually through inoculation. The threshold for herd immunity against measles, for example, is quite high — about 95%, according to the World Health Organization. In comparison, the threshold for polio is about 80%.
Strategies for boosting childhood vaccinations
Last month, editors at the leading scientific journal Nature urged policymakers to consult academic research to determine which interventions work best at boosting vaccination rates.
“The burgeoning science of vaccine-uptake effectiveness is throwing up some unexpected results that could help public-health authorities to sharpen their policies — and save more lives,” the editors write in a July 9 editorial.
An example: In 2021, the White House announced a new program that offered free rides to vaccination sites to encourage Americans to get a COVID-19 booster shot. But a study published in Nature in June finds that providing a free round-trip Lyft ride to a CVS pharmacy “does not produce measurable benefits over and above reminding people to get vaccinated.”
Studies published in recent years suggest these four strategies may help improve childhood vaccination rates. Detailed summaries of key papers that examine these interventions are located toward the bottom of this article.
- Offering inoculations at schools, libraries and other places children and their families frequent.
- Providing incentives such as financial rewards to families and to health care providers who administer vaccines to children.
- Eliminating exemptions to school vaccine requirements, except for students with medical conditions that prevent them from receiving vaccines.
- Reducing the number of kids admitted to school before they have received all doses of all required vaccines. Many schools allow students to enroll on a “provisional” or “conditional” basis while they catch up on their shots.
Vaccine exemptions
Psychology scholar Dolores Albarracín says schools send families mixed messages about the importance of childhood vaccinations when they allow a lot of kids to skip immunizations. In Idaho, for instance, families can request vaccine exemptions for any reason. Schools there gave exemptions to 12.1% of kindergartners statewide in 2022-23, more than in any other state, CDC data show. In Oregon and Utah, the rate exceeded 8%.
Nationwide, 3% of kindergarteners — about 115,000 kids — obtained exemptions from state-required vaccinations in 2022-23. That’s up from 2.6% the prior year.
Albarracín, who is director of the Communication Science Division at the University of Pennsylvania’s Annenberg Public Policy Center, has studied vaccination policies. A paper she coauthored, published in Nature’s Scientific Reports in December, suggests vaccination policies can alter social norms and change people’s attitudes toward vaccines.
Like the American Medical Association and American Academy of Pediatrics, Albarracín supports eliminating vaccine exemptions that are not directly tied to a student’s medical condition.
“How can schools be trying to really ensure [vaccination] if, at the same time, they’re allowing parents to not vaccinate kids for all these personal and religious reasons?” she asks.
School vaccination requirements
Children must be vaccinated against certain communicable diseases to attend school in the U.S. School vaccination mandates vary by state but generally apply to both public and private schools, including charter schools and parochial schools.
All states require kids to receive these four vaccines prior to enrolling in kindergarten:
- 2 doses of MMR, which protects against measles, mumps and rubella.
- 5 doses of DTaP, which protects against diphtheria, tetanus and acellular pertussis.
- 2 doses of VAR, which provides immunity against varicella, also known as chickenpox.
- 4 doses of Polio, which helps prevent poliomyelitis, commonly referred to as polio.
All states also allow exemptions to these requirements, according to the National Conference of State Legislatures, which tracks student immunization policies. As of August 2023, every state provided exemptions to students for medical reasons such as having a weakened immune system or being allergic to a component of a required vaccine.
Religious exemptions are common, too. All but five states offer them. Fifteen states grant exemptions for children whose parents object to immunizations because of personal or moral beliefs or other reasons.
In 2015, California banned all exemptions that were not for medical reasons, becoming the first state in almost three decades to do so. At the time, only West Virginia and Mississippi prohibited non-medical exemptions.
In 2019, New York and Maine eliminated religious exemptions, followed by Connecticut in 2021.
Various groups have challenged such policies, however. Last year, a federal judge in Mississippi sided with several parents who argued that not being able to skip state-required vaccines on religious grounds violated their First Amendment rights. In April 2023, the court ordered Mississippi, known for its high MMR vaccination rate among kindergarteners, to begin offering religious exemptions.
Early this year, the West Virginia legislature passed a bill that would have loosened school vaccine policies there, in part by letting private schools set their own standards. But Gov. Jim Justice vetoed the measure March 27.
Focusing on under-vaccinated kids
Epidemiologist Sarah Michels says states could boost vaccination rates quite a bit by focusing on children who have started a vaccine series but not yet finished it. Michels has conducted national studies of infants and toddlers and found that many are just one or a few doses away from being fully vaccinated.
This is relevant because most doses of the four vaccines schools require are administered to children before age 2, provided their families follow the immunization schedule the CDC recommends.
“Most families choose to vaccinate their infants and children, and what we saw is that more than 1 in 6 kids are missing doses,” explains Michels, an epidemiology specialist at the University of Montana’s Center for Population Health Research.
A study she led, published in Pediatrics last year, suggests the main reason more young children are not immunized is because of various barriers families face in accessing vaccines — not because they fear or object to vaccines. For lower-income families, it can be difficult to make time or afford transportation to vaccination clinics and medical offices.
“We found that moving across state lines, higher numbers of children in the household, lacking health insurance, lower household income, living in a rented home, and race and ethnicity were each associated with a 20% or greater risk of failure to complete multidose vaccine series in early childhood,” Michels and her colleagues write in their paper.
Some 2.5% of U.S. kindergarteners were allowed to attend school without having received all doses of their required vaccines in 2022-23, the CDC reports. The percentage of 5- and 6-year-olds who were provisionally or conditionally enrolled varied by state, reaching as high as 9.2% in Arkansas.
Growing opposition to vaccination mandates
Vaccines were a polarizing issue in the U.S. before the COVID-19 pandemic began. But a 2022 analysis from researchers at Baruch College and Fordham University finds that the political divide in attitudes toward vaccines has widened over the last decade.
“By 2015, a partisan spit emerged across not only vaccine attitudes, but also in reported vaccination behavior,” political scientists David R. Jones and Monika L. McDermott write in the working paper. While Republicans “have become more vaccine skeptical,” they add, Democrats “have become more vaccine supportive.”
Vaccines have become a key issue in this year’s presidential election. Last month, former President Donald Trump told supporters at a rally in Minnesota that if he is reelected in November, he “will not give one penny to any school that has a vaccine mandate or a mask mandate.” Vice President Kamala Harris, on the other hand, has spoken in favor of vaccines broadly.
This year and last year, lawmakers in several states have pushed to make it easier for students to get vaccine exemptions and to ensure parents know what exemptions are available. For example, in Idaho, a state law that took effect in July allows students 18 years and older to request school vaccine exemptions for themselves. A state law enacted in Louisiana this year requires schools to include information about vaccine exemptions in all communications with parents about vaccine requirements.
A new Gallup poll quantifies changing attitudes toward childhood vaccinations. Americans are far less likely to say immunizations are important than they were before COVID-19 spread to the U.S. in early 2020, Gallup notes in an Aug. 7 press announcement.
Today, 69% of U.S. adults think it’s “very important” or “extremely important” that parents get their kids vaccinated. When Gallup conducted similar polls in 2015 and 2019, 84% of U.S. adults believed that.
Americans are also much less likely to believe the government should mandate vaccinations against contagious diseases such as measles. The Gallup survey, conducted in July with a nationally representative sample of 1,010 people, reveals that 45% of U.S. adults think the government “should stay out of” the issue.
In 2019, that number was 35%. Back in 1992, 14% of Americans felt that way, Gallup notes.
Research roundup
A Systematic Review and Meta-Analysis of Strategies to Promote Vaccination Uptake
Sicong Liu, et al. Nature Human Behavior, August 2024.
The study: Researchers analyzed research conducted in recent decades to determine which interventions work best to encourage immunization. They combined and examined the results of 88 randomized, controlled trials conducted with a total of 1.6 million people across age groups in 17 countries.
This meta-analysis, which was pre-registered in August 2022, evaluates seven strategies, including broadening access to vaccines, sending vaccination reminders, providing incentives, supplying information and correcting misinformation. The interventions studied targeted various vaccines, including the flu vaccine, the COVID-19 vaccine and routine childhood vaccines.
Key findings: The researchers found that the most effective interventions offered incentives such as cash rewards and made it easier for people to find and get immunizations. “Providing incentives, however, is presumably most effective when they are valued by their recipients, guaranteed to be delivered and delivered immediately after vaccination,” the authors write.
Enhancing access to vaccines — for example, offering vaccinations in places people frequent — “holds the most promise in lower-income countries or countries with lower healthcare access.”
In the authors’ words: “We showed that the odds of vaccination were 1.5 times higher for intervention than control conditions. Among the intervention strategies, using incentives and increasing access were most promising in improving vaccination uptake, with the access strategy being particularly effective in countries with lower incomes and less access to healthcare.”
Failure to Complete Multidose Vaccine Series in Early Childhood
Sarah Y. Michels, et al. Pediatrics, July 2023.
The study: Researchers estimate the percentage of U.S. babies and toddlers who have not received the all doses of seven recommended vaccines. The researchers also investigate the reasons why a substantial proportion of young children start but do not finish at least one vaccine series. The analysis is based on national data for 16,365 children aged 19 to 35 months, collected from the 2019 National Immunization Survey.
Key findings: Most young children — 72.9% — completed the seven-vaccine series. About 1.1% were completely unvaccinated. Meanwhile, 8.4% lacked just one dose of one vaccine and 17.2% started but did not finish at least one vaccine series. Children were most likely to miss doses of the MMR and VAR vaccines.
Children from lower-income households and children who lived in rental homes were 25% to 30% more likely to be missing vaccine doses. “Having multiple immunization providers increased in the risk of starting but failing to complete all series by approximately 50%,” the researchers write. Black children were less likely than white children to complete a vaccine series.
In the authors’ words: “More than 1 in 6 U.S. children initiated but did not complete all doses in multidose vaccine series, suggesting children experienced structural barriers to vaccination. Increased focus on strategies to encourage multidose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals.”
Coverage with Selected Vaccines and Exemption from School Vaccine Requirements Among Children in Kindergarten — United States, 2022-23 School Year
Ranee Seither, et al. Morbidity and Mortality Weekly Report, November 2023.
The study: Researchers analyze federal data on vaccination rates among kindergarteners in the U.S. during the 2022–23 school year. They provide several charts outlining vaccination rates and vaccination exemption rates in the 50 states and District of Columbia.
Key findings: Vaccination rates for all four state-required vaccines declined in most of the U.S. In 2022-23. About 93% of kindergartners had received all doses of the four vaccines, down from 95% in 2019-20. The nationwide exemption rate was 3%, compared with 2.6% the prior year. In 10 states, more than 5% of kindergartners were exempted from at least one vaccine. Exemption rates ranged from less the 0.1% in West Virginia to 12.1% in Idaho.
In the authors’ words: “Schools and providers should work to ensure that students are vaccinated before school entry, such as during the enrollment process, which is often several months before school starts. State and local provisional enrollment periods that allow students to attend school while on a catch-up schedule also provide the opportunity to fully vaccinate students and to prevent nonmedical exemptions resulting from lingering under-vaccination due to COVID-19 pandemic–related barriers to vaccination, such as reduced access to vaccination appointments.”
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