University Hospital in Newark, New Jersey is mandating Covid booster shots for employees who got the Johnson & Johnson vaccine. “Data and analysis indicate a single dose of the Johnson & Johnson vaccine may no longer confer a level of effectiveness that prevents COVID-19 infection in enough of our employees if they are exposed, which has implications on our ability to keep vulnerable patients and families safe,” President and CEO of the hospital Dr. Shereef Elnahal said in a statement.