In 2021 a good quality study was done with 187 healthy children age 4-12 years, which showed that taking an echinacea purpurea supplement could reduce antibiotic usage for respiratory tract infections by up to 32%, compared to taking Vit C.

https://www.naturalmedicinejournal.com/.../reduction...

If your kids frequently come home with respiratory infections from daycare and school, this may be common and normal, but it isn't necessarily ideal. Especially if it sometimes leads to needing to take antibiotics, which can damage the microbiome.

A scientific review of current literature has also recommended that echinacea is a potential force against coronavirus infections, including Covid-19, in both adults and children.

Echinacea is known to have broad antiviral activity in humans, however at this stage it can only be said that:

"Preliminary published clinical results on SARS-CoV-2 may yet further support the use of Echinacea also against this particular coronavirus."

https://www.mdpi.com/2076-2607/10/2/211/htm