This study found up-to-date vaccination coverage from children 24 months of age and younger declined in all age cohorts except the birth-dose hepatitis B coverage. 

• Among children aged 5 months, up-to-date status for all recommended vaccines declined from approximately two thirds of children during 2016–2019 (66.6-67.9%) to fewer than half (49.7%) in May 2020. For the 16-month age cohort, coverage with all recommended vaccines declined, with measles-containing vaccination coverage decreasing from 76.1% in May 2019 to 70.9% in May 2020.
• Furthermore, up-to-date series coverage for each age cohort (1, 3, 5, 7, 16, 19, and 24 months) assessed in May 2020 was lower for Medicaid-enrolled children than for those children not enrolled in Medicaid.
  • The largest difference was in the age 7 months cohort assessed in May 2020; in that cohort, 34.6% of Medicaid-enrolled children were up-to-date for their recommended series, compared with 55.0% of children not enrolled in Medicaid
• In summary, the observed declines in vaccination coverage might leave young children and communities vulnerable to vaccine-preventable diseases such as measles. If measles vaccination coverage of 90%–95% (the level needed to establish herd immunity) is not achieved, measles outbreaks can occur. Concerted efforts are needed to ensure rapid catch-up for children who are not up-to-date with measles-containing vaccines as well as other ACIP-recommended vaccinations