Strong antibody response and nasal cytokines may protect young children from severe COVID-19

Recent research helps explain why young children have lower rates of severe COVID-19 than adults. A study of infants and young children found those that acquired SARS-CoV-2 had a powerful, sustained antibody response to the virus and high levels of inflammatory proteins within the nose but not within the blood. This immune response contrasts with that typically seen in adults with SARS-CoV-2 infection. Co-funded by the National Institute of Allergy and Infectious Diseases (NIAID), a part of the National Institutes of Health, the research appears within the journal Cell.

The investigation involved 81 full-term infants and young children whose moms enrolled in a NIAID-supported cohort study at Cincinnati Kid’s during their third trimester of pregnancy. The study team trained moms to gather weekly nasal swabs from their infants starting when the babies were 2 weeks old. The team also drew blood from the babies frequently, starting at age 6 weeks, in addition to when the youngsters became infected with SARS-CoV-2 and through subsequent weeks and months.

These samples enabled the scientists to review the youngsters’s immune responses before, during and after they were exposed to the virus for the primary time. Fifty-four of the youngsters became infected and had mild COVID-19, while 27 who tested negative through the study period served as matched controls. On the time of infection, the youngsters were 1 month to almost 4 years old, and half were 9 months or younger. The study also included weekly nasal swabs from 19 moms with COVID-19 and 19 healthy moms as controls, in addition to blood samples from 89 adults with COVID-19 and 13 healthy controls.

The researchers examined many points of the babies’ and adults’ immune responses to the virus through an approach called systems immunology. The study revealed that young kid’s antibody response to SARS-CoV-2 differs from that of adults. Typically, adults produce antibodies to the virus at levels that spike for a couple of weeks, then decline. In contrast, the infants and young children within the study produced protective antibodies at levels that spiked and remained high for as much as the total 300-day remark period.

The scientists also found that the blood of adults with SARS-CoV-2 infection typically had high levels of proteins called inflammatory cytokines, that are related to severe COVID-19 and death, while the blood of babies and kids didn’t. Nevertheless, the youngsters’s noses had high levels of inflammatory cytokines and a potent antiviral cytokine.

In keeping with the researchers, these findings suggest that cytokines snuffed out SARS-CoV-2 infection right at the location where the virus entered the youngsters’s bodies, potentially explaining the mildness of their COVID-19 disease. The findings also suggest it could be possible to plot vaccine adjuvants that mimic the immune responses observed in young children by stimulating persistently high antibody levels without causing dangerous excess inflammation within the blood.

Children aged 6 months to 4 years who got COVID-19 vaccines before September 12, 2023, should get one or two doses of updated COVID-19 vaccine, depending on which vaccine and what number of doses they previously received. Children aged 6 months to 4 years who haven’t been vaccinated should get two or three doses of updated COVID-19 vaccine, depending on which vaccine they receive.

Bali Pulendran, Ph.D., and Mary Allen Staat, M.D., M.P.H., led the study. Dr. Pulendran is the Violetta L. Horton Professor and co-director of the Institute for Immunology, Transplantation and Infection at Stanford University in California. Dr. Staat is the Kulkarni Endowed Chair in Infectious Diseases and a professor of pediatric infectious diseases at Cincinnati Kid’s.