Babies Under 6 Months Are Hospitalized With COVID-19 at High Rates

Key findings

• Infants under 6 months are too young for COVID-19 vaccine. They depend on antibodies from their mothers, passed across the placenta after vaccination or infection.
• From October 2023 to April 2024, their COVID-19 hospitalization rate — 319.8 per 100,000 — was higher than every other age group's except adults 75 and older (940.1), and similar to that of adults 65–74 (284.2).
• Among about 1,000 hospitalized infants, 22% went to intensive care, and nine died in hospital.
• The share of hospitalized infants whose mothers had been vaccinated during pregnancy fell from 18% in October 2022–September 2023 to under 5% in October 2023–April 2024.

Hospitalization rates

From October 2022 to April 2024, the COVID-19–Associated Hospitalization Surveillance Network (COVID-NET), covering 90 counties in 12 states, recorded 1,470 COVID-19 hospitalizations of infants under 6 months.

• Their weekly rates were higher than any other children's age group, peaking at 23.0 per 100,000 in the week ending December 17 in 2022–23, and 20.3 in the week ending January 13 in 2023–24.
• Over October–April, the rate fell from 413.6 in 2022–23 to 319.8 in 2023–24.

Weekly COVID-19 hospitalization rates by children's age group, October 2022–April 2024. Figure from the CDC report.

The infants

Charts were fully reviewed for 1,266 infants. The 118 newborns who tested positive during the hospital stay in which they were born were left out of the clinical analysis, because a positive test then is hard to interpret: only 18.3% of them had COVID-19 symptoms, against 92.6% of the 1,148 others.

Among those 1,148 infants:

• Age and stay: median age at admission 64 days; median stay 2 days.
• Severity: 22.1% (260) were admitted to intensive care, and 0.8% (nine) died in hospital. 21.4% needed high-flow nasal oxygen or BiPAP/CPAP breathing support, and 4.8% (56) mechanical ventilation.
• Health conditions: about a quarter (24.0%) had at least one — most often prematurity (17.1%), cardiovascular disease (6.6%), chronic lung disease (4.7%) and neurologic disorders (3.3%).
• Other viruses: of those tested, 29.7% had at least one — respiratory syncytial virus in 19.3%, rhinovirus/enterovirus in 12.2% and influenza in 1.9%. Among infants in intensive care who were tested, 41.2% had another virus, and 25.1% had respiratory syncytial virus.

Mothers' vaccination

Mothers' vaccination status was known for 1,065 infants, and 87.5% (921) of their mothers had no record of COVID-19 vaccination during pregnancy.

• The vaccinated share fell from 17.6% (132 of 745) in 2022–23 to 4.3% (12 of 320) in 2023–24.
• Infants of vaccinated mothers were older when hospitalized — median 109 days, against 58.
• Of the infants who died in hospital and whose mother's status was known, every one had a mother with no record of vaccination during pregnancy.

Hospitalized infants by mothers' vaccination status during pregnancy, by age group and season. Figure from the CDC report.

What it means

Infants under 6 months are among the people hardest hit by COVID-19: too young to be vaccinated, they generally lack immunity from past infection. Vaccination during pregnancy has been shown to be safe and effective at keeping young infants out of hospital, and CDC recommends COVID-19 vaccination for everyone 6 months and older, including during pregnancy. Yet coverage is low: a 2023 survey found that nearly a quarter (24.7%) of pregnant people had a COVID-19 vaccination during pregnancy.

To protect pregnant people and babies too young to be vaccinated, prevention should focus on making sure pregnant people get recommended COVID-19 vaccines, alongside hand hygiene and keeping infants away from people with respiratory symptoms.

Limits

Mothers' vaccination records may be incomplete; with no population estimates for infants under 6 months, rates used half the population under 1 year; not every hospitalized infant may have been tested; and the network covers about 10% of the U.S. population, in selected counties of California, Colorado, Connecticut, Georgia, Maryland, Michigan, Minnesota, New Mexico, New York, Oregon, Tennessee and Utah.

Sources

Based on Fiona P. Havers, Michael Whitaker, Bhoomija Chatwani, Monica E. Patton, Christopher A. Taylor and colleagues, "COVID-19–Associated Hospitalizations and Maternal Vaccination Among Infants Aged <6 Months — COVID-NET, 12 States, October 2022–April 2024," MMWR, Centers for Disease Control and Prevention; a work of the United States government in the public domain.