Are infants younger than six months at higher risk of SARS-CoV-2 infections?

In a recent study posted to the medRxiv* preprint server, a team of researchers in the United States examined the incidence and associated characteristics of medically attended coronavirus disease 2019 (COVID-19) episodes in infants below six months of age.

Study: Incidence Rates of Medically Attended COVID-19 in Infants Less than 6 Months of Age. Image Credit: Sopotnicki / Shutterstock

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections were initially believed to affect adults more than children, but surveillance data suggest that infants under a year old may be more likely to be hospitalized as a result of COVID-19 than older children.

Recent studies indicate that while infants below one year experience mild to moderate symptoms of SARS-CoV-2 infections, the rate of hospitalization among that age group is still disproportionate compared to other pediatric COVID-19-related hospitalizations. However, these studies lack robust sampling and do not analyze outcomes according to demographic factors. A comprehensive analysis of COVID-19 incidence among infants is essential for public health policies and expectant parents to understand and manage disease risks.

About the study

In the present study, the team used the medical record data between March 1, 2020, and February 28, 2021, from the Epidemiology of SARS-CoV-2 in Pregnancy and Infancy (ESPI) Network: Electronic Cohort (eESPI) to analyze medically attended COVID-19 incidence including outpatient care cases and hospitalizations among infants less than six months old.

The eESPI data comprised information from three United States (U.S.) health care systems and included maternal and infant cohorts. The participants in the maternal cohort had a delivery date during the study period and had at least one prenatal telemedicine or outpatient hospital visit between December 1, 2019, and February 28, 2021. Participants with pregnancy losses during the study period were excluded from the dataset. The infant cohort consisted of all infants born to the mothers included in the maternal cohort.

The International Classifications of Diseases 10 (ICD-10) codes and positive SARS-CoV-2 real-time-polymerase chain reaction (RT-PCR) tests were used to define medically attended COVID-19 episodes. In addition, demographic data and medical conditions of the mothers and infants, prenatal medical visit history, and data on telemedicine, ambulatory care, emergency department visits, and hospitalizations were also included in the study.

Additionally, factors such as documented COVID-19 in mothers during pregnancy or in the postpartum period, gestational age at delivery, and sites and levels of SARS-CoV-2 circulation were considered while estimating the incidence rates.

Results

The results indicate a 0.95% rate of COVID-19 incidence among more than 18,000 infants born between March 2020 and February 2021 and followed up for six months post birth. Most of these were outpatient or telemedicine visits, with only 0.1% of the infant cohort requiring hospitalization.

Factors such as maternal SARS-CoV-2 infection status, community transmission, infant age, and the mother’s race or ethnicity influenced the incidence rates. Compared to COVID-19 diagnoses in mothers during pregnancy or after delivery, postpartum maternal SARS-CoV-2 infections were associated with higher rates of medically attended COVID-19 in infants. This suggested potential horizontal SARS-CoV-2 transmission from mother to infant and possible community acquisition of COVID-19.

Analysis of medically attended COVID-19 incidence rates according to race and ethnicity indicated a higher incidence among infants born to Hispanic and Non-Hispanic Black mothers, suggesting an increased COVID-19 burden among minority populations.

Additionally, infants with COVID-19 revealed more underlying medical conditions than infants without COVID-19. This could be attributed to infants with medical conditions getting tested more often for SARS-CoV-2 during frequent healthcare visits than generally healthy infants.

Some of the limitations discussed by the authors include maternal COVID-19 vaccination status not being accounted for in the analysis and the inability of the study to assess the impact of SARS-CoV-2 circulation levels and clinical testing practices on the incidence rates. Furthermore, the study was conducted during the first year of the COVID-19 pandemic, and the results cannot be generalized to SARS-CoV-2 variants and subvariants.

Conclusions

To summarize, the study assessed the incidence rates of medically attended COVID-19 in infants below six months of age according to maternal COVID-19 status during pregnancy and the postpartum period, race or ethnicity of the mother, underlying medical conditions in mother and infant, and community transmittance.

The findings indicate that during the first year of the pandemic, incidence rates among infants younger than six months were very low, with medically attended COVID-19 cases being related to underlying medical conditions in infants. Furthermore, the highest COVID-19 incidence occurred in infants of mothers with SARS-CoV-2 infections during the postpartum period.

The study emphasizes the need for COVID-19 vaccinations for mothers before or during the pregnancy and for family members and other caregivers to limit horizontal and community transmittance of COVID-19 to infants.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.