Key Differences Between Children and Adults with COVID-19

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Key Differences Between Children and Adults with COVID-19

New Research Reveals Key Differences Between Children and Adults with COVID-19

Recent research findings have unveiled why young children exhibit fewer severe symptoms of COVID-19 when compared to adults.

The study observed that infants infected with SARS-CoV-2 mount a robust and sustained antibody response to the virus, with high levels of inflammatory proteins in their nasal secretions and blood. This immune response sharply contrasts with that of adults infected with SARS-CoV-2.

This research was jointly funded by the National Institute of Allergy and Infectious Diseases (NIAID) under the National Institutes of Health and was published in the journal “Cell.”

Key Differences Between Children and Adults with COVID-19

Research Methods and Participants

The investigation involved 81 full-term infants whose mothers participated in the NIAID-supported cohort study at Cincinnati Children’s Hospital in late pregnancy.

The research team trained mothers to collect nasal swabs from their infants weekly starting at 2 weeks of age.

Blood samples were also regularly drawn from the infants, beginning at 6 weeks of age and following children who became infected with SARS-CoV-2 in the subsequent weeks and months.

Among the participants, 54 children were infected with mild COVID-19, while 27 children tested negative throughout the study as a matched control group.

The infected children ranged in age from 1 month to nearly 4 years, with most being 9 months or younger.

The study also included weekly nasal swabs from 19 mothers with COVID-19 and 19 healthy mothers as controls, as well as blood samples from 89 adults with COVID-19 and 13 healthy controls.

Key Findings: Child vs. Adult Immune Responses

Researchers examined various aspects of infants and adults’ immune responses to the virus using a method known as systems immunology. The study showed that infants’ antibody responses to SARS-CoV-2 differ from those of adults. Typically, virus antibody levels produced by adults spike for a few weeks and then decline. In contrast, the protective antibody levels produced by infants and young children in the study spiked and remained high over an observation period of up to 300 days.

Scientists also found that the blood of infected adults usually contains high levels of proteins called inflammatory cytokines, which are associated with severe COVID-19 and death, while the blood of infants and children does not. However, children’s nasal secretions have high levels of inflammatory cytokines and effective antiviral cytokines.

Implications and Recommendations

According to the researchers, these findings suggest that cytokines at the site where the virus enters children’s bodies may thwart SARS-CoV-2 infection, possibly explaining the mildness of their COVID-19 illness. The results also suggest the possibility of designing vaccine adjuvants that mimic the immune response observed in infants by stimulating sustained high antibody levels without causing dangerous excessive inflammation in the blood.

Children aged 6 months to 4 years who were vaccinated against COVID-19 before September 12, 2023, should receive one or two booster doses of the COVID-19 vaccine, depending on their previous vaccine and dose history. Unvaccinated children in the same age group should receive two or three booster doses of the COVID-19 vaccine, depending on the vaccine they initially received.

Dr. Bali Pulendran and Dr. Mary Allen Staat led this research. Dr. Pulendran is the Violetta L. Horton Professor and co-director of the Immunology, Transplantation, and Infection Institute at Stanford University in California. Dr. Staat is the Kulkarni Chair in Infectious Disease and a professor of pediatric infectious disease at Cincinnati Children’s Hospital.