Young kids rarely get very sick from COVID-19, finds a new study - Video

As a rule, infants and young children rarely develop severe or enduring cases of COVID-19. And those who do almost invariably suffer from some other serious medical problem.

It's not that kids don't get infected. They do. More than 90% of kids age 4 and under in the United States test positive for previous or current infection by SARS-CoV-2, the coronavirus that causes this respiratory infection.

"For almost every infectious disease, the most vulnerable populations are at the extremes of age -- the very young and the very old," said Stanford Medicine professor of microbiology and immunology and of pathology Bali Pulendran, PhD. "But with COVID-19, the young are spared while the old are emphatically not. That's been a mystery."

There's evidence for these and other hypotheses. But much of the solution to the mystery COVID-19 poses may reside inside little kids' noses.

In the blood of SARS-CoV-2-infected adults, SARS-specific antibody levels rose quickly to a robust peak, then dropped off precipitously, declining by 10-fold within six months.

Infants' blood-borne antibodies to SARS-CoV-2 were a little slower to spike upward in response to SARS-CoV-2 infection. But in stark contrast to adults, their antibody levels never dropped -- they either plateaued at a high level or kept on rising throughout the 300-day observation period, eventually rivaling those of the adults at peak.

The kids' antibodies, he noted, tended to be somewhat narrow spectrum: highly effective against the original invading variant, but providing less protection against other SARS-CoV-2 variants.

Reference: Florian Wimmers, Allison R. Burrell, Yupeng Feng, Hong Zheng, Prabhu S. Arunachalam, Mengyun Hu, Sara Spranger, Lindsay E. Nyhoff, Devyani Joshi, Meera Trisal, Mayanka Awasthi, Lorenza Bellusci, Usama Ashraf, Sangeeta Kowli, Katherine C. Konvinse, Emily Yang, Michael Blanco, Kathryn Pellegrini, Gregory Tharp, Thomas Hagan, R. Sharon Chinthrajah, Tran T. Nguyen, Alba Grifoni, Alessandro Sette, Kari C. Nadeau, David B. Haslam, Steven E. Bosinger, Jens Wrammert, Holden T. Maecker, Paul J. Utz, Taia T. Wang, Surender Khurana, Purvesh Khatri, Mary A. Staat, Bali Pulendran. Multi-omics analysis of mucosal and systemic immunity to SARS-CoV-2 after birth. Cell, 2023; 186 (21): 4632 DOI: 10.1016/j.cell.2023.08.044