Kroger Co. /zigman2/quotes/206215053/composite KR +1.38% said Wednesday that fully vaccinated customers and most fully vaccinated workers will not be required to wear a mask in stores, at distribution centers, and in other facilities starting May 20. Pharmacy and clinic associates will still be required to wear a mask. Non-vaccinated associates will still have to wear a mask, and the grocer is encouraging non-vaccinated customers to do so as well. Enhanced cleaning and social distancing messaging will continue, and the company will continue to offer a $100 incentive to get the vaccine. Kroger joins a list of retailers, including Walmart Inc. /zigman2/quotes/207374728/composite WMT +0.11% and Target Corp. /zigman2/quotes/207799045/composite TGT +1.26% that have relaxed their mask rules in light of the CDC's latest guidelines. Kroger stock is up 14.8% for the year to date while the S&P 500 index /zigman2/quotes/210599714/realtime SPX +0.01% is up 9.4% for the period.