What is the risk of severe COVID-19 in infants younger than three months?

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In a recent study published in Viruses, a team of researchers from Italy investigated the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in infants younger than three months and compared the reported coronavirus disease 2019 (COVID-19) severity scores for the pediatric population.

Study: COVID-19 in Infants Less than 3 Months: Severe or Not Severe Disease? Image Credit: M M Vieira/Shutterstock
Study: COVID-19 in Infants Less than 3 Months: Severe or Not Severe Disease? Image Credit: M M Vieira/Shutterstock


Evidence suggests that severe COVID-19 symptoms are not as prevalent in the pediatric population as in the adult population worldwide. However, some studies have reported that infants and children with comorbidities are at a higher risk of increasing severity. A population cohort study in the United Kingdom showed that SARS-CoV-2 infections in the neonatal population led to 42% of severe cases, with 33% requiring respiratory support.

Contrasting studies indicate that infants with SARS-CoV-2 infections are either asymptomatic or exhibit mild symptoms, and the severe COVID-19 cases among the neonatal population were associated with premature birth and cardiac abnormalities.

Studies also differ in the basis on which the severity of COVID-19 is scored, with some studies scoring the severity on epidemiological symptoms. In contrast, others use clinical manifestations in test results as a basis. Yet another study used clinical outcomes such as the mechanical ventilation requirement or the development of organ dysfunction as the basis for severity scores.

About the study

The present study used data collected from a network of 62 pediatric medical institutions across Italy to understand the outcomes and epidemiological and clinical aspects of severe COVID-19 in infants younger than 90 days. A positive quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) test was used to confirm the presence of COVID-19. The anonymized data comprised information on vaccination history, previous medical conditions, laboratory test reports, hospitalization records, diagnostic procedures, prescribed medications, and disease outcomes.

The severity was scored based on various criteria used in previous studies. The severity score scale for assessing COVID-19 outcomes ranged from one to four. Score one indicated a diagnosis of pneumonia with oxygen saturation being normal or mildly low and hospitalization without intensive care unit requirements, and four denoted deaths. Mild COVID-19 cases which did not satisfy the criteria for scores one to four were assigned a score of zero.


The results were consistent with those from other studies and reported that a large proportion of the infected infants below three months of age had mild symptoms or were asymptomatic. The common symptoms in neonates and infants mostly consisted of fever, runny nose, and cough. Infants were more likely to have gastrointestinal symptoms such as vomiting and diarrhea than adults.

Severe symptoms such as respiratory distress, lethargy, and loss of appetite were not frequently reported. Among the neonatal cohort in the study, there were nine cases of early-onset COVID-19 (within the first week from birth), and the remaining 50 cases were late onset (during weeks two to four from birth).

The authors hypothesized that early-onset COVID-19 cases in neonates are most likely due to congenital or peripartum transmission of SARS-CoV-2. At the same time, late-onset incidences were best explained by contact with maternal respiratory fluids, other infected household members, or healthcare staff. Furthermore, the study identified a household member with COVID-19 in 58.5% of cases of late-onset neonatal SARS-CoV-2 infection. The results also found that 2.8% of the cases originated in the hospital, highlighting the need for increased COVID-19 monitoring and usage of personal protective equipment in hospitals.

Contrary to previous studies, the present cohort study indicated very low levels of leukocytosis and lymphopenia during complete blood counts. Still, the authors believe that this could be due to the limited number of severe COVID-19 cases in their study. Furthermore, inflammatory markers such as C-reactive protein, ferritin, and lactate dehydrogenase were abnormal only in a small percentage of patients. Some studies reported elevated creatine phosphokinase and liver enzymes, which was not observed in the current study.

Most cases were treated symptomatically with antipyretics and antibiotics. None of the patients required antivirals, and only one infant was prescribed hydroxychloroquine. Hospitalizations were required mostly due to the young age of the patients.

According to the authors, the severity classification differed based on the scoring criteria. It highlighted the ambiguity in the current definitions of COVID-19 severity, indicating the need for a validated a priori severity scoring system.


Overall, the study corroborated the findings from other studies and reported that severe COVID-19 manifestations are rare in infants younger than three months of age. Among the patients, late-onset SARS-CoV-2 infections were more frequent than early-onset cases and were mostly attributed to contact with an infected household member, and in rare cases, with infected hospital workers.

The various severity classification criteria used in the literature make the scoring of COVID-19 symptoms ambiguous, indicating a need for a generalized, validated scale for grading the severity of SARS-CoV-2 infections.

Journal reference:
Dr. Chinta Sidharthan

Written by

Dr. Chinta Sidharthan

Chinta Sidharthan is a writer based in Bangalore, India. Her academic background is in evolutionary biology and genetics, and she has extensive experience in scientific research, teaching, science writing, and herpetology. Chinta holds a Ph.D. in evolutionary biology from the Indian Institute of Science and is passionate about science education, writing, animals, wildlife, and conservation. For her doctoral research, she explored the origins and diversification of blindsnakes in India, as a part of which she did extensive fieldwork in the jungles of southern India. She has received the Canadian Governor General’s bronze medal and Bangalore University gold medal for academic excellence and published her research in high-impact journals.


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