Vaccines are increasingly under threat in the U.S. Dr. Donald Vinh looks at what that might mean for the spread of infectious diseases and for Canada. Subscribe to CTV News to watch more videos: https://www.youtube.com/ctvnews Connect with CTV News: For live updates and latest headlines visit: http://www.ctvnews.ca/ For breaking news, fast, download the CTV News App: https://www.ctvnews.ca/app Must-watch stories and full programs at http://www.ctvnews.ca/video CTV News on TikTok: https://www.