U.S. to reopen Canada, Mexico borders to vaccinated people but exclude those with mixed vaccines

After 19 months, the United States will soon reopen its Canadian and Mexican borders to vaccinated people.

While that's welcome news for those who've hoped to see friends in family in the U.S., the Centers for Disease Control and Prevention still won't allow people with two different vaccines to enter.

Host Tonya Mosley discusses the science of "mix and match" doses with Helen Branswell of STAT.