The measles vaccine uses a weakened virus that's never been shown to spread to others. Samples from the outbreak in Texas also show that a wild-type virus is responsible. Yet, social media posts have falsely claimed that the outbreak is due to a vaccine strain.

The measles vaccine has been proven to be safe and effective against the disease, which is highly contagious and can be life threatening.

Texas and New Mexico health departments said on Friday that the number of measles cases in their states rose 20% since their last reports three days ago, as experts warn they expect the outbreak to further spread in coming weeks.

Measles is continuing to spread across the Texas Panhandle and South Plains regions breaking 300 cases on Friday.

The parents of an unvaccinated 6-year-old Texas girl who died from measles said they still wouldn't recommend vaccinations during an interview with an anti-vaccination organization last week.

Measles cases in the U.S. neared 500 Friday, according to the CDC, as the highly contagious illness continues spreading in Texas after being reported in at least 18 other states.

The total number of cases reported in the state since January is 400. The total number of measles cases reported in connection with a West Texas outbreak has reached 400, according to the latest data from the Texas Department of State Health Services. In Friday's update, the agency reported 73 new cases since Tuesday.

Kennedy made a show of shipping vitamin A to measles-stricken communities. The state’s public-health department didn’t take up the offer.