other links:
https://health.clevelandclinic.org/are-cloth-masks-enough-against-omicron/
https://www.deseret.com/coronavirus/2021/12/29/22858397/cloth-masks-stop-omicron-variant-covid-19
Basically Omicron produces a lot more virus (because it's so much more infectious than delta or alpha) when you inhale and exhale so encounters that didn't result in infection with alpha or delta might result in infection with omicron.