• Monarez says Kennedy demanded pre-approval for vaccine decisions
• Former CDC director appearing before Senate HELP Committee
• Kennedy replaced vaccine advisers with anti-vaccine activists
• Kennedy criticism grows after Monarez firing, CDC resignations

WASHINGTON, Sept 17 (Reuters) - Former U.S. CDC Director Susan Monarez told a Senate panel on Wednesday that Health Secretary Robert F. Kennedy Jr. required her to seek her own political staff's approval for her policy and personnel decisions before ultimately firing her.