It is important to do all you can to improve the health and functioning of your immune system, naturally. Then, seriously consider what additional protection would be gained from vaccination against COVID-19.

Are multivitamins of any benefit, or do they just make expensive urine?

Depression is more than just a lack of serotonin. Inflammation is likely a major driver.

If you are 18 or older, and in an area where there is a COVID-19 outbreak, the best vaccine for you is the one you can get right now.