The World Health Organisation has listed vaccine hesitancy as one of the top 10 threats to global health in 2019.
The US is having its biggest measles outbreak in 25 years, while there have been several reported outbreaks of the disease in recent years in the UK.
More than half a million children in the UK were unvaccinated against measles between 2010 and 2017, according to figures released by Unicef.
The situation has forced the health secretary to consider imposing mandatory jabs for the disease.
So why, when there is a safe vaccination against the potentially deadly disease, are people deciding not to have it?
What is measles?
Measles is the most infectious illness known to man and is much easier to catch than flu or Ebola, according to Public Health England.
Adults, children and babies can contract the viral illness, which is spread through millions of tiny droplets that come out of the nose and mouth when an infected person coughs or sneezes.
Measles is still a major cause of child deaths around the world.
Measles vaccination - the evidence
Last year, the UK celebrated 50 years since the MMR (measles, mumps, rubella) vaccine was introduced.
Public Health England estimates that 20 million measles cases and thousands of deaths have been prevented in the UK since the introduction of the vaccine in 1968.
Before 1968, the number of measles cases was anywhere between 160,000 and 800,000 each year, with 100 UK deaths from acute measles annually.
In 2016, the UK achieved measles elimination status, which means it is no longer native to the UK.
However, this does not mean it has disappeared, as people living in the UK travel to other countries and bring strains of the virus back.
When and why did people stop vaccinating?
In 1998, a study by British doctor Andrew Wakefield was published in The Lancet linking the MMR vaccine to autism.
The study was discredited, but not before causing mass hysteria over the safety of the vaccine after the study received global media coverage.
MMR immunisations in the UK fell to about 80% nationally in the late 1990s and early 2000s and took many years to recover.
In 2006, measles transmission became re-established in the UK, and in 2007, cases of measles exceeded 1,000 for the first time in 10 years.
The Lancet retracted Wakefield's study in 2010, and he was struck off the UK medical register.
But the anti-vax movement is still thriving.
Why are vaccination numbers still low, more than 20 years on?
It's not just Wakefield's now discredited study that led people to decide against immunising their children.
However, his disproven link to autism has gained new traction with the emergence of social media.
People also cite religious reasons for opting out of vaccinations, as well as philosophical reasons.
There is also growing doubt and reluctance to trust large pharmaceutical companies, as more people believe they seek to only profit from drugs and don't care about public health.
A combination of these factors, along with the ease with which these opinions can be shared and spread online, have made people increasingly sceptical and fearful about whether vaccinations are safe, and in the public's best interest.
However, vaccinations are proven to prevent potentially deadly diseases.
Dr Ellie Cannon told Sky News: "Vaccination is one of the greatest public health successes, saving millions of lives globally from diseases like meningitis to Polio.
"Not vaccinating your child puts them at risk of serious illness and death: why would parents choose that?"
What threat does measles currently pose?
Between 1 January 2018 and 31 October 2018, there were 913 confirmed cases in England.
This is compared to 259 cases in the whole of 2017.
The sharp rise is associated with outbreaks linked to travel to Europe, particularly among teenagers and young adults who missed out on their MMR vaccine when they were younger, according to the NHS.
The US is currently having its largest outbreak in 25 years.
The worst affected city has been New York, particularly the Orthodox Jewish communities in Brooklyn, according to the US Centres for Disease Control and Prevention and city public health officials.
Last year a similar outbreak occurred in London's Orthodox Jewish areas, thought to be due to close-knit communities.
The current outbreak in the US is also linked to travel from Ukraine, and in the last year there have also been measles outbreaks in Europe and elsewhere.
Preliminary global data by the World Health Organisation shows that reported cases rose by 300% in the first three months of 2019, compared to the same period in 2018.