What is already known about this topic?
Infants aged <6 months, who are ineligible for vaccination, have high COVID-19–associated hospitalization rates compared with other pediatric age groups.
What is added by this report?
Although population-based COVID-19–associated hospitalization rates among infants aged <6 months increased in the Omicron variant–predominant periods compared with the Delta variant–predominant period, indicators of the most severe disease among hospitalized infants aged <6 months did not.
What are the implications for public health practice?
Pregnant women should stay up to date with COVID-19 vaccination to help protect themselves and infants too young to be vaccinated. Nonpharmaceutical measures should be used to help protect infants ineligible for vaccination.