Washington (AP) — U.S. regulators say they are no longer considering authorizing second COVID-19 booster shots for all adults under 50 this summer. Instead the Food and Drug Administration said it will await revamped vaccines targeting the newest viral subvariants that are expected by September. Some members of the Biden administration had been pressing regulators to open a fourth dose of the Moderna and Pfizer shots to all adults before the fall. They had argued that another round of booster shots now could help head off rising cases and hospitalizations caused by the highly transmissible omicron strains.