ABC News medical contributor Dr. Alok Patel gives tips for staying healthy as the world enters the fourth year of the pandemic. #covid #variant #who #pandemic #healthy #abcnews #abcnlupdate abcabcnlCoronavirusCOVID-19COVID19covid19 immunityimmune systemIMMUNITYnewsomicronp_cmsid=2494279p_vid=news-96337748subvarianttransmissibleUpdateVITAMINWHO