"We take very seriously the expressed concerns that mercury in vaccines causes autism and remain committed to full implementation of AB 2943," Belshe said. Belshe issued the waiver at the request of the California branch of the American Academy of Pediatrics, Kaiser Permanente, the California Medical Association and the California Academy of Family Physicians.  Because of delays in vaccine production, pediatricians have received only partial orders of the mercury-free influenza shots and thus have not been able to protect young children as the flu season approaches, the medical groups said. Yet many doctors have flu shots available with thimerosal. Gov. Arnold Schwarzenegger endorsed the temporary waiver and fired off a letter Thursday to Sanofi Pasteur, the lone manufacturer of mercury-free children's vaccine, encouraging the firm to beef up its production. The firm expects to fill all of its orders by the end of November, a spokeswoman said.