If you want early intervention, we all need to make sure our immune system is adequately facilitated! To do that requires sufficient levels of blood Vit D. Our levels of Vit D drop quite dramatically over the age of 50 (hence higher death rates in the elderly to the flu and of course Covid). It's also why during winter when the sun is lower on the horizon it's more difficult to manufacture sunlight Vit D that is why it is more likely to be the flu season. We have one at the moment but it doesn't get much of a mention as Covid is the current flavour !!!! If you want to ensure against Covid, the flu and common cold, which are all virus related make sure your levels of blood Vit D are adequate. If unsure have a Vit D blood test. Then if necessary dose up on the various Vit D supplements available!. That is the best insurance and intervention against Covid!!! Zinc and Magnesium with Vit D are a more effective combination!