Research has shown clearly that people who have the best nutrition also have the least amount of sickness. One major risk factor for COVID that has stood out is a zinc deficiency. Many pharmaceuticals cause zinc deficiency and this is why COVID affects the older population more than the young.
The second major risk factor is vitamin D deficiency. 80% of people who had severe COVID infections were also severely deficient in vitamin D which basically disables your immune system.
My recommendation for all adults to take daily is this:
Vitamin D 5000 IU daily. It is safe to take megadoses of vitamin D so if you miss a few days you can take them all at once.
Zinc 50mg daily. This is a great maintenance dose for zinc for adults. If you feel like you are coming down with a viral infection you can take this dose 5 time daily for 5 days. Viruses cannot replicate in the presence of zinc.
Vitamin C 500mg twice daily. The more vitamin C you take the better, not just for your immune system but for your general heal, antioxidant effect and for your bones. High doses can cause diarrhea but your body will adapt to this and you can increase your intake over time as your body tolerates it.
Elderberry syrup 1 tablespoon daily during the winter months. Take 1 tablespoon 4-5 times a day if you are sick. Elderberry syrup has quercetin and powerful antioxidants. Research shows that is is MORE effective than Tamiflu and does not cause the heart valve problems or psychiatric side effects that Tamiflu is known for. I do not recommend Tamflu under any circumstance because the risk far outweighs the benefit.
Last but not least, if you develop a fever it is best that you DO NOT take Tylenol or ibuprofen (motrin) for the fever unless you are just so miserable that you can't stand it. Fever is one of the most powerful ways to fight any infection so leave it alone and let your immune system do what it is designed to do. Virus and bacteria cannot survive these high temperatures.