Everybody should be taking the following:
-Vitamin D (min 3000iu/day); bring your serum D level to at least 55ng/mL or to higher.
-Zinc and Quercetin which acts as ionophore for Zinc. Quercetin is also a potent antioxidant that is good for many other reasons
-Vitamin C from natural sources, not ascorbic acid
-Elderberry
-Adrenal supporting adaptogens. People that had healthy, less stressed out adrenals survived the Spanish Flu.
-Traditional Chinese Medicine on hand in case you get breakthrough infections. TCM in fact is perfect for treating/preventing Long Covid that can't be managed by Western Medicine. Ban Lan Gen for example was sold out in Hong Kong and other parts of the country during the first SARs-1 outbreak because it is a broad-spectrum antiviral.
If you are worried about productivity and Covid, then most Chinese citizens should be taking these as they significantly reduce the chance of catching severe covid/long covid, lessen symptoms, prevents hospitalization when combined with masks and vaccines.