This was one in a continuing line of moves that have put Kennedy's vaccine skepticism into public policy, though scientists say the vaccines are safe.

The targeting of the vaccine technology once considered revolutionary follows intense criticism by conservatives and anti-vaccine activists.

U.S. Health Secretary Robert F. Kennedy Jr. incorrectly argued mRNA vaccines are ineffective to justify the Department of Health and Human Service's recent decision to cancel $500 million in government-funded research projects to develop new vaccines using the technology.