"Vaccinations are so important," Trump told reporters at the White House. "They need to get their shots."
The extent of the measles epidemic in the United States – with 695 cases registered since January 1st – is frozen by the situation in Ukraine, which has around 25,000 patients and Madagascar with 46,000 cases of the disease.
But it was enough to put US health authorities on the brink, with shining light on a number of vulnerable communities where parents left their children unvaccinated – much wrapped up by a wider "anti-vaxxer" movement that refuses the benefits of vaccinations or allegations they are dangerous .
In the United States, more than 91 percent of children received the first dose of measles, mumps and rubella vaccine (MMR) until the age of three.
But the sense of anti-vaccine – often driven by misinformation – has sent immunization rates to fall into so-called pockets.
This year's rebuilding – the highest since the announcement of the disease nearly two decades ago – is concentrated in three strong Jewish areas in Brooklyn, the Rockland area near New York, near Detroit and in a community in the Russian language in Washington State.
Earlier this month, the mayor of New York declared a public health emergency in the strong Orthodox Jewish parts of Brooklyn, ordering all residents to be vaccinated.
And Californian authorities announced on Thursday that more than 250 people at two universities have been quarantined because health workers are struggling to contain highly contagious disease.
The Department of Public Health said hundreds of students and employees at the University of California Los Angeles (UCLA) and the California State University (Cal State) were exposed to measles carrier earlier this month.
Those who could not prove they were inoculated were quarantined, they said.
In the past, Trump has given some support to the anti-vaccination movement, claiming, for example, that severe infant doses may be associated with autism.
"Massive combined inoculations for young children cause a major rise in autism," Trump told Twitter in 2012.
He reiterated this message while running for president in 2015.
"Autism became an epidemic. 25 years ago, 35 years ago, you see the statistics and not even closed. It's completely out of control. I'm generally in favor of the vaccines. But I want smaller doses over a longer period of time "Trump said during the presidential initial debate of CNN.
The anti-vaxx movement, based on the scientifically disclosed British report of 1988, linking the MMR vaccine with autism, has increased in recent years with the rise of social media conspiracy theories.
Repeated studies – the last involving more than 650,000 children monitored for more than a decade – have shown that such a relationship does not exist.
About 169 million children miss the vital dose of measles vaccine between 2010 and 2017, according to a UNICEF report.
The number of cases of illness rose by 300 percent in the world in the first three months of 2019 compared to the same period last year, the UN said.
The anti-vaxxer movement has supporters across the western world, but is a particularly high profile in the US.
The US epidemic is partly blamed for unvaccinated visitors who touch the disease during visits to Israel and Ukraine.
The New York epidemic is followed by Orthodox Jews from Brooklyn visiting Israel, and then the spread of highly contagious disease through synagogues, schools, and housing blocks among children whose parents did not iconise them.
In Clark County, Washington, the disease spreads among the Russian-speaking community after a child returned the virus from Ukraine in December and expanded to 74 other people, mostly children, through schools, supermarkets and bowling alley.
Ukraine, which suffered a five-year bleeding conflict with Russia on its eastern border region, has killed at least 11 people.
Smallpox is one of the most polluting viruses in the world. It spreads by coughing or sneezing, the virus can lie in the air long after the infected person leaves the room.