Americans who received the Johnson & Johnson coronavirus vaccine are less protected against serious illness and hospitalization and should get an mRNA booster, the CDC found in a new study. The Centers for Disease Control and Prevention reported that the J&J shot’s efficacy lags well behind vaccines from Pfizer/BioNTech and Moderna. It recommends that the roughly 17 million people in the U.S. who received the single-dose shot get a messenger RNA booster. The report is just the latest blow to Johnson & Johnson, which has been plagued by missteps since it rolled out its vaccine in February 2021….