WASHINGTON — The Department of Health and Human Services will cancel contracts and pull funding for some vaccines that are being developed to fight respiratory viruses like COVID-19 and the flu.

Robert F. Kennedy Jr. announced in a statement Tuesday that 22 projects, totaling $500 million, to develop vaccines using mRNA technology will be halted.

Kennedy’s decision to terminate the projects is the latest in a string of decisions that have put the longtime vaccine critic’s doubts about shots into full effect at the nation’s health department. Kennedy has pulled back recommendations around the COVID-19 shots, fired the panel that makes vaccine recommendations, and refused to offer a vigorous endorsement of vaccinations as a measles outbreak worsened.

The health secretary criticized mRNA vaccines in a video on his social media accounts, explaining the decision to cancel projects being led by the nation’s leading pharmaceutical companies, including Pfizer and Moderna, that offer protection against viruses like the flu, COVID-19 and H5N1.

“To replace the troubled mRNA programs, we’re prioritizing the development of safer, broader vaccine strategies, like whole-virus vaccines and novel platforms that don’t collapse when viruses mutate,” Kennedy said in the video.