Trump tells Americans measles vaccination 'so important'

US President Donald Trump has given some support to the anti-vaccination movement in the past. [AFP]

President Donald Trump on Friday urged Americans to get vaccinated as a measles outbreak spread across the country, reaching the highest number of cases since 2000.

"Vaccinations are so important," Trump told reporters at the White House. "They have to get their shots."

The scale of the measles outbreak in the United States -- with 695 recorded cases since January 1 -- is dwarfed by the situation in Ukraine, which has clocked up some 25,000 patients and Madagascar with 46,000 cases of the disease.

But it has been enough to set US health authorities on edge, shining a light on a number of vulnerable communities where parents have left their children unvaccinated -- many swayed by a wider "anti-vaxxer" movement which rejects the benefits of vaccinations or claims they are dangerous.

Across the United States, more than 91 percent of children have received the first dose of the measles, mumps and rubella (MMR) vaccine by age three.

But anti-vaccine sentiment -- often fueled by disinformation -- has sent immunization rates plummeting in so-called pockets.

This year's US caseload -- the highest since the disease was declared eliminated almost two decades ago -- has been concentrated in three heavily Jewish areas in Brooklyn, Rockland County near New York, and near Detroit, and in a Russian-speaking community in Washington State.

Earlier this month New York's mayor declared a public health emergency in heavily Orthodox Jewish parts of Brooklyn, ordering all residents to be vaccinated.

And California authorities said Thursday that more than 250 people at two universities have been quarantined as health officials battle to contain the highly-infectious disease.

The Department of Public Health said hundreds of students and staff at the University of California Los Angeles (UCLA) and California State University (Cal State) had been exposed to a measles carrier earlier this month.

Those who couldn't prove they had been inoculated had been quarantined, it said.

In the past, Trump has given some support to the anti-vaccination movement, claiming, for example, that heavy doses given to young infants may be linked to autism.

"Massive combined inoculations to small children is the cause for big increase in autism," Trump said on Twitter in 2012.

He reiterated that message while running for president in 2015.

"Autism has become an epidemic. Twenty-five years ago, 35 years ago, you look at the statistics, not even close. It has gotten totally out of control. I am totally in favor of vaccines. But I want smaller doses over a longer period of time," Trump said during a presidential primary debate on CNN.

Global Spread

The anti-vaxxer movement, based on a scientifically debunked 1988 British report linking the MMR vaccine to autism, has surged in recent years with the rise of online conspiracy theories on social media.

Repeated studies -- the most recent involving more than 650,000 children monitored for more than a decade -- have shown that there is no such link.

An estimated 169 million children missed out on the vital first dose of the measles vaccine between 2010 and 2017, according to a UNICEF report.

The number of cases of the disease had risen 300 percent worldwide in the first three months of 2019 compared to the same period last year, the UN said.

The anti-vaxxer movement has adherents across the Western world but is particularly high profile in the United States.

The US outbreak has been blamed in part on unvaccinated visitors contracting the disease during visits to both Israel and Ukraine.

The New York outbreak has been traced to Orthodox Jews from Brooklyn visiting Israel, then spreading the highly infectious disease through synagogues, schools and apartment blocks to children whose parents had not had them inoculated.

In Clark County, Washington, the disease has spiked among the Russian-speaking community after a child brought the virus back from Ukraine in December and it spread to 74 other people, mostly children, through schools, supermarkets and a bowling alley.

Ukraine, which has experienced five years of simmering conflict with Russia on its eastern border region, has had at least 11 people die from the illness.

Measles is one of the world's most contagious viruses. Spread by coughing or sneezing, the virus can linger in the air long after an infected person leaves a room.