Most children who are infected with SARS-COV2, the virus that causes COVID, experience only mild symptoms or no symptoms at all. But a small proportion develop severe illness which can sometimes even require hospital care.

The reason why only some children develop severe illness hasn’t been clear until now. But our latest study provides new insights into the immune responses associated with severe respiratory infections such as COVID.

Our study analysed blood gene expression profiles from 333 South African children with similar genetic backgrounds. A gene expression profile measures the activity of thousands of genes simultaneously. Analysing them can tell us whether some genes have been switched “on” or “off” in response to an infection.

Of these children, 127 were considered healthy, 71 had mild or asymptomatic COVID, 41 were hospitalised with severe COVID, 47 were hospitalised with a respiratory syncytial virus (RSV) infection and 47 had pulmonary tuberculosis. Only children who were exposed to a single respiratory infection were included. We also adjusted our analyses for age.

Our study........

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