Washington (AFP) – The US said Thursday only adults who “have personal concerns” about mRNA vaccines, access issues or medical reasons for refusing them may now receive the Johnson & Johnson Covid shot, which has been linked to a rare but serious clotting condition. The vaccine, which was authorized as a single shot, is less protective than those developed by Pfizer and Moderna, and in December the Centers for Disease Control and Prevention advised the public to steer clear. Thursday’s decision by the Food and Drug Administration builds on that recommendation by limiting the J&J vaccine’s emer…