Childhood Vaccination Fell Among U.S. Children Born in 2020 and 2021

This page summarizes a CDC report on children born in 2020–2021, surveyed during 2021–2023, with measles counts through August 15, 2024.

The Advisory Committee on Immunization Practices (ACIP) recommends that children be vaccinated against 15 potentially serious illnesses by age 24 months. Since 1994, CDC's National Immunization Survey-Child (NIS-Child) has tracked how many children get those vaccines. Its latest analysis gave a first look at children born in 2021, who turned 2 around or after the end of the COVID-19 public health emergency, and found that children born in 2020 and 2021, during or after the worst of the pandemic's disruption to primary care, were less likely to be vaccinated than those born just before.

How the survey works

NIS-Child calls mobile phones at random to find households with a child aged 19 to 35 months and interviews the parent who knows most about the child's vaccinations. With the parent's consent, it then mails a questionnaire to each of the child's vaccine providers and builds a full vaccination history from their records. All the estimates below come from providers' records. In the 2023 survey, the household response rate was 27.0% and adequate provider data were available for 48.1% of children interviewed; children born in 2020–2021 were identified in the 2021–2023 surveys, giving 28,688 children to analyze.

Coverage fell for almost every vaccine

Compared with children born in 2018–2019, coverage by age 24 months was lower for every recommended vaccine except the hepatitis B birth dose and 2 or more doses of hepatitis A vaccine. Most declines ranged from 1.3 percentage points (1 or more doses of varicella vaccine) to 3.2 points (the full Hib series and the combined seven-vaccine series). Coverage with 2 or more doses of flu vaccine dropped 7.8 points. Earlier NIS-Child analyses, of children born in 2017–2020, had found no consistent or lasting national declines.

Apart from flu vaccine, the biggest drops were for doses due in the second year of life: the fourth dose of DTaP (diphtheria, tetanus and pertussis), the last dose of the Hib series and the fourth dose of pneumococcal conjugate vaccine.

Flu vaccination had been rising for years, but among children born in 2021 it fell to 53.4%, more than 10 points below the 63.8% for children born in 2019. Healthy People 2030's target for children receiving no vaccines (1.3% or fewer) has been met, but its targets for MMR (at least 90.8%) and 4 doses of DTaP (at least 90.0%) have not.

Who was left behind

• Race and ethnicity. Coverage with 4 doses of DTaP, 4 doses of pneumococcal vaccine, rotavirus vaccine and the combined series was lower among Black, Hispanic, and American Indian or Alaska Native children than among White children. Flu vaccine coverage was lower among Black and Hispanic children, and higher among Asian children, than among White children.
• Insurance. Coverage with every vaccine was lower among children on Medicaid or other nonprivate insurance, and among uninsured children, than among those with only private insurance.
• Poverty. Coverage with every vaccine was lower among children below the federal poverty level, by 2.7 percentage points (MMR) up to 19.9 points (flu vaccine).
• Rural areas. Children outside metropolitan areas had lower coverage than those in a metropolitan area's principal city for every vaccine except the full Hib series, the hepatitis B birth dose and hepatitis A. There was no difference between principal cities and other parts of metropolitan areas.
• Place. Coverage varied widely by state, most of all for flu vaccine, from 25.6% in Mississippi to 80.3% in Rhode Island. Comparing the two birth cohorts state by state across eight vaccine measures found 69 statistically significant differences, 64 (92.8%) of them declines.

Why it may be happening

Several studies have documented the pandemic's harm to routine childhood vaccination. Parental vaccine hesitancy may also play a part, especially for flu vaccine, which parents are more hesitant about than other routine vaccines, and hesitancy about flu vaccine tracks more closely with hesitancy about COVID-19 vaccine than with hesitancy about other childhood vaccines. One analysis found hesitancy rose after COVID-19 vaccine was authorized among parents of children aged 5–11, though not among parents of children aged 6 months to 4 years. Nonstandard vaccination schedules and growing use of religious and philosophical exemptions are further barriers.

Caveats

Response rates were low (21%–27% in 2019–2023), and adequate provider data were available for only 48%–54% of interviewed children, which may bias the results despite weighting. Households without phones are not reached; if they are more often lower-income, observed coverage would be higher than the truth. And the 2023 provider records were probably incomplete: a contract problem shortened the time for collecting them and the provider questionnaire changed from one page to two. An assessment of total survey error for 2023 found coverage underestimated by 2.0 points for MMR, 4.3 for the hepatitis B birth dose, 5.1 for 4 doses of DTaP and 9.4 for the combined series.

What is at stake

Falling coverage could bring back diseases such as measles, varicella and rotavirus. From January 1 to August 15, 2024, 219 measles cases were reported in the United States, more than in any full year from 2020 to 2023 (which ranged from 13 in 2020 to 121 in 2022); 190 of them (86%) were in people who were unvaccinated or whose vaccination status was unknown.

The authors urge providers to review every child's vaccination history and recommend any vaccines they are missing at every visit, since children born during the pandemic may have missed some. Other steps that work:

• wider provider participation in the Vaccines for Children program, which provides vaccines at no cost
• reminder and recall systems, standing orders and clinician prompts
• strong recommendations from providers
• vaccination in alternative settings
• using immunization information systems to find communities with low coverage

Sources

• Hill HA, Yankey D, Elam-Evans LD, et al. "Decline in Vaccination Coverage by Age 24 Months and Vaccination Inequities Among Children Born in 2020 and 2021 — National Immunization Survey-Child, United States, 2021–2023." MMWR 73(38). https://www.cdc.gov/mmwr/volumes/73/wr/mm7338a3.htm
• Supplementary figure and tables: https://stacks.cdc.gov/view/cdc/162212, https://stacks.cdc.gov/view/cdc/162213, https://stacks.cdc.gov/view/cdc/162214; 2023 error profile: https://www.cdc.gov/childvaxview/media/pdfs/2024/09/Error-Profile-2023-NIS-Child.pdf