Vaccine exemption rate rises among US kindergarteners
The rate of vaccine exemptions rose slightly among children entering kindergarten in the 2018-2019 school year, with 2.5% having an exemption from at least one vaccine, according to new data published in MMWR. But researchers suggested an additional target to improve vaccine coverage rates in the United States: underimmunized children who begin school under grace periods or provisional enrollment.
In some states, children who were provisionally enrolled in school or within a grace period surpassed the number of children with vaccine exemptions.
“Children may be enrolled under a grace period or provisional enrollment because parents do not have complete records for all the vaccinations children have received or because children do not have all required vaccinations due to missed opportunities for vaccination or to temporary medical contraindications,” Ranee Seither, MPH, an epidemiologist in the CDC’s Immunization Services, told Infectious Diseases in Children. “Most parents do have their children vaccinated, so it makes sense that more parents would choose to use a grace period or provisional enrollment to have a child catch up on missing vaccines or obtain complete documentation of a child’s vaccination history and not to ask for a vaccine exemption. In the event of an outbreak, these children could be at risk and excluded from school for their own protection.”
Seither added that vaccination in these children can be improved with follow-up.
The researchers analyzed data collected by both state and local vaccination programs for overall coverage for more than 3.6 million kindergarteners in 49 states. They also identified vaccine exemptions among more than 3.6 million kindergarteners in 50 states and surveyed more than 2.8 million children in 30 states for entering school under a grace period or provisional enrollment.
According to Seither and colleagues, immunization programs reported that 4,001,404 children began kindergarten during the 2018-2019 school year in the U.S. Among them, two-dose coverage of MMR vaccine was 94.7%, below the 95% coverage required to achieve herd immunity against measles. Coverage varied from state to state, with Colorado reporting the lowest coverage (87.4%) and Mississippi the highest (at least 99.2%).
According to the researchers, 20 states achieved at least 95% MMR coverage during the school year, but coverage was below 90% in Colorado and Idaho.
Immunization programs reported DTaP coverage of 94.9% for kindergarteners entering school, with rates ranging from 88.8% in Idaho to more than 99.2% in Mississippi. Similar to the MMR vaccine, 20 states reported vaccine coverage of at least 95%, but four states reported coverage of less than 90%.
Varicella vaccine coverage reached 94.8% nationally, with the researchers reporting a range of 86.5% in Colorado to at least 99.2% in Mississippi.
Gaps in coverage
More children beginning school in the 2018-2019 year — 2.5% — had vaccine exemptions for one or more required vaccines compared with kindergarteners beginning school in the 2016-2017 year (2.1%) and the 2017-2018 school year (2.3%), Seither and colleagues reported. The states with the highest rate of exemptions were Idaho and Oregon (7.7%), whereas Mississippi reported only 0.1% of kindergarteners with a vaccine exemption. Most children with a vaccine exemption who started school in 2018-2019 had a nonmedical exemption (2.2%), and 0.3% had a medical exemption.
Seither and colleagues noted the rise in vaccine exemptions, but also expressed concerns about children who enrolled undervaccinated under a grace period or under provisional enrollment. They reported that 2% of kindergarteners in 30 states began school undervaccinated, ranging from 0.2% in Georgia to 6.7% in Ohio. In 10 of the 30 states, more children were enrolled under these provisions compared with those who received vaccine exemptions.
According to the researchers, almost all states could achieve at least 95% MMR coverage if undervaccinated nonexempt children were vaccinated according to local and state policies.
“Recent measles outbreaks in states with high overall MMR coverage show how important it is for states to use school-level data to identify where local vaccination efforts are needed,” Seither said. “Providers can help increase school vaccination coverage by making sure that kindergarten-aged patients are up to date with ACIP-recommended vaccines and state school entry vaccination requirements.”
Factors affecting immunization rates
A second study published in MMWR tracked vaccine coverage for children born between 2015 and 2016. Although coverage remained high for this birth cohort by age 24 months, Holly A. Hill, MD, PhD, a medical officer at the CDC’s Immunization Services Division, told Infectious Diseases in Children that the study revealed several areas for improvement.
“Coverage was lower for children without private health insurance, especially those with no insurance, as well as those living below the poverty level and in more rural areas,” she said. “These disparities suggest challenges with access to affordable vaccinations or optimal vaccination services.”
Hill and colleagues noted that the CDC’s Advisory Committee on Immunization Practices suggests that children should receive vaccinations against 14 diseases by age 24 months. To examine the percentage of children who received the recommended number of doses of these vaccines, the researchers analyzed national, state and territorial data on children born during the study period. Some local data were included in the report.
Overall, immunization rates were high among children born between 2015 and 2016. Most received at least three doses of poliovirus vaccine (92.7%), at least one dose of MMR (90.4%), at least three doses of hepatitis B vaccine (91%) and at least one dose of varicella vaccine (90%).
According to Hill and colleagues, vaccination rates increased 3.2 percentage points for the HBV birth dose, 1.5 percentage points for at least one dose of hepatitis A vaccine and 3.6 percentage points for at least two doses of influenza vaccine compared with children born between 2013 and 2014.
Furthermore, the researchers reported that more children received at least two doses of HAV vaccine by age 35 months when they were born between 2015 and 2016 compared with those born between 2013 and 2014 (76.6% vs. 74%).
During the study period, those who were not up to date on recommended immunizations by age 24 months were most likely to be late on at least two doses of influenza vaccine (56.6%) and the combined seven-vaccine series (68.5%).
According to Hill and colleagues, uninsured children and those with Medicaid or other nonprivate insurance coverage had lower immunization rates compared with children covered by private insurance. Specifically, the researchers identified a 7.8 percentage point disparity for the HBV birth dose between privately insured and uninsured children, whereas a 33.8 percentage point difference was reported for at least two doses of influenza vaccine.
Uninsured children also were more likely to be unvaccinated compared with privately insured children (7.4% vs. 0.8%). Demographic factors including race and/or ethnicity, poverty level and metropolitan statistical area influenced vaccine coverage.
The researchers noted that vaccination coverage for recommended vaccines by age 24 months was only stable for 1 birth year between 2011 and 2016, and the proportion of unvaccinated children increased 0.09 percentage points annually during this time.
“Increased opportunity for vaccination can be facilitated by expanded access to health insurance, greater promotion of available vaccines through the Vaccines for Children program and solutions to logistical challenges such as transportation, child care and time off from work,” Hill said. “Providers can improve coverage overall and reduce disparities by administering all recommended vaccinations during office visits. Compelling and accessible educational materials can be used to counter inaccurate claims about vaccination and communicate the value of vaccines in protecting the health of children.” – by Katherine Bortz
Disclosures: The authors report no relevant financial disclosures.