of norway. 5 people dead and 2 injured. a man with a bow and arrow shot in a number of locations. later arrested. described as a danish man, a muslim convert. flagged as being radicalized. that attack was the deadliest in norway in 10 years. >> dana: and a new study about mixing and matching covid vaccine for immune response for booster shots especially for johnson & johnson who got a second shot from moderna or pfizer. mark has an update. >> they are trying to understand how effective the booster shots are. there is a suggestion that boosters provide added protection even in the booster doesn't match the vaccine you had previously. the study involved 458 people and researchers measured antibodies after 2 and 4 weeks.