WATCH: Trump stresses importance of vaccines amidst measles outbreak, says people 'have to get their shots'

Measles is making a resurgence in the United States, and President Donald Trump wants people to get vaccinated in response.

"They have to get their shots," the president told reporters outside the White House on his way to the National Rifle Association's annual meeting in Indianapolis. "The vaccinations are so important.

"This is really going around now," he continued. "They have to get their shots."

In the past, President Trump has been publicly pro-vaccine but has expressed concerns about the potential side effects of giving young children a lot of them in a short window of time.

"I am totally in favor of vaccines. But I want smaller doses over a longer period of time," candidate Trump said at a 2015 GOP primary debate. "Same exact amount, but you take this little beautiful baby, and you pump — I mean, it looks just like it's meant for a horse, not for a child, and we've had so many instances, people that work for me."

And despite widespread media coverage of some of his 2014 tweets on the subject, President Trump's Centers for Disease Control clearly states that "there is no link between vaccines and autism."

Measles is a virus that can be serious and even fatal for small children, the Mayo Clinic explains, it kills around 100,000 people annually. It is evidenced by respiratory symptoms and a telltale rash.

The U.S. is currently seeing its worst year for measles cases since the disease was declared eliminated almost 20 years ago, according to the CDC.

As of Wednesday afternoon, the agency reported a total of 695 cases of measles across 22 different states and attributed the sum primarily to large outbreaks in Washington state and New York.

"This current outbreak is deeply troubling and I call upon all healthcare providers to assure patients about the efficacy and safety of the measles vaccine," CDC Director Robert Redfield said in a a statement. "And, I encourage all Americans to adhere to CDC vaccine guidelines in order to protect themselves, their families, and their communities from measles and other vaccine preventable diseases. We must work together as a Nation to eliminate this disease once and for all."