Matcha tea, raw cacao are best for everyday prevention.
Upon getting any symptoms (sore throat, cough), take 300mg Quercetin, wait 30 min, then take 30mg (chelated) zinc (pref. w copper). If sore throat also gargle w warm water + sea salt.
i dont know where things stand with using Viagra to treat COVID but I remember reading about using it for people dealing with high altitude sickness..which wrapped around to people chewing on the coca leaves for high altitude in the rare countries that allow it.