Incidence Rates of Medically Attended COVID-19 in Infants Less than 6 Months of Age

Objective Studies suggest infants may be at increased risk of severe COVID-19 relative to older children, but few data exist regarding the incidence of COVID-19 episodes and associated risk factors. We estimate incidence rates and describe characteristics associated with medically attended COVID-19 episodes among infants younger than 6 months of age. Methods We analyzed electronic medical record data from a cohort of infants born March 1, 2020‒ February 28, 2021. Data from three health care delivery systems included demographic characteristics, maternal and infant outpatient visit and hospitalization diagnoses, and SARS-CoV-2 test results. Medically attended COVID-19 episodes were defined by positive SARS-CoV-2 clinical tests and/or COVID-19 diagnosis codes during medical care visits. Unadjusted and site-adjusted incidence rates by infant month of age, low and high SARS-CoV-2 circulation periods and maternal COVID-19 diagnosis were calculated. Results Among 18,192 infants aged <6 months whose mothers received prenatal care within the three systems, 173 (1.0%) had medically attended COVID-19 episodes. Incidence rates were highest among infants aged under 1 month (2.0 per 1,000 person-weeks) and 1 month (2.0 per 1,000 person-weeks) compared with older infants. Incidence rates were also higher for infants born to women with postpartum COVID-19 compared with women without known COVID-19 and women diagnosed with COVID-19 during pregnancy. Conclusion Most medically attended COVID-19 episodes in infants aged <6 months were outpatient care encounters. Infants of women with postpartum COVID-19 had a higher risk of medically attended COVID-19 than infants born to mothers who were diagnosed during pregnancy or never diagnosed underscoring the importance of COVID-19 prevention measures for their household members and caregivers to prevent infections in infants. Article Summary This report describes incidence rates and characteristics of medically attended outpatient and inpatient COVID-19 episodes among infants aged <6 months during the COVID-19 pandemic. What’s Known on This Subject Surveillance data and case series suggest that infants aged <1 year may be more likely to be hospitalized with COVID-19 than older children, but few data are available about the risk of medically attended COVID-19 episodes among infants. What this Study Adds Among infants aged <6 months, few were hospitalized with COVID-19. Incidence rates of medically attended COVID-19 episodes were highest among infants aged ≤ 1 month and among infants of women with COVID-19 during the 6 month post-partum period.