Something concerning is happening to our children. Unlike previous autumns, this year there seem to be far more kids falling ill, and far too many needing serious medical attention — to the point that our pediatric hospitals are overwhelmed. Critical surgeries are being cancelled. Teenagers are being transferred to adult ICUs. Some of these children have died.

The culprits are relatively common viruses that come in seasonal waves: respiratory syncytial virus (RSV) and influenza. By any account, this year’s respiratory virus season is much worse (and arrived much earlier) than in the pre-pandemic period. Not surprisingly, many wonder what role the COVID-19 pandemic may be playing. In fact, two very different hypotheses have been proposed: immunity debt and immunity theft.