The World Health Organization has listed vaccination hesitation as one of the ten biggest threats to global health in 2019.
The US has their largest measles outbreak in 25 years, while there have been several reported outbreaks of the disease in the UK in recent years.
More than half a million children in the UK were not vaccinated against measles between 2010 and 2017, according to figures released by Unicef.
The situation has forced the health secretary to impose mandatory jabs for the disease.
So why, when there is a safe vaccination against the potentially deadly disease, do people decide not to have it?
What is measles?
Measles is the most contagious disease known to humans and is much easier to catch than flu or ebola, according to Public Health England.
Adults, children and babies can contract the viral disease, which is spread by millions of tiny droplets coming out of the nose and mouth when an infected person coughs or sneezes.
Measles is still a major cause of infant mortality all over the world.
Measles vaccination – the proof
Last year the UK celebrated 50 years ago that the BMR vaccine (measles, mumps, rubella) was introduced.
Public Health England estimates that 20 million measles and thousands of deaths have been prevented in the UK since the vaccine was introduced in 1968.
Before 1968, the number of measles cases was anywhere between 160,000 and 800,000 a year, with 100 British deaths each year as a result of acute measles.
In 2016, the UK achieved measles elimination status, meaning that it is no longer native in the UK.
However, this does not mean that it has disappeared because people living in the UK travel to other countries and bring the virus back.
When and why did people stop vaccinating?
In 1998, a study by British physician Andrew Wakefield was published in The Lancet that linked the MMR vaccine to autism.
The study was discredited, but not before mass hysteria was caused about the safety of the vaccine after the study received worldwide media coverage.
MMR vaccines in the UK fell to around 80% at the national level in the late 1990s and early 2000s and took many years to recover.
In 2006 the measles transfer was relocated to the UK and in 2007 exceeded cases of measles exceeded 1,000 for the first time in 10 years.
The Lancet withdrew Wakefield's study in 2010 and was withdrawn from the British medical register.
But the anti-vax movement is still flourishing.
Why are vaccination rates still low, more than 20 years later?
It is not only the now-discredited Wakefield study that has led people to decide not to immunize their children.
His denied link to autism, however, has left new marks with the rise of social media.
People also quote religious reasons to opt out of vaccinations and for philosophical reasons.
There is also growing doubt and reluctance to trust large pharmaceutical companies because more people believe they only want to take advantage of drugs and not enjoy public health.
A combination of these factors, together with the ease with which these opinions can be shared and disseminated online, has made people increasingly skeptical and anxious about whether vaccinations are safe and in the public interest.
However, it has been proven that vaccinations prevent potentially fatal diseases.
Dr. Ellie Cannon told Sky News: "Vaccination is one of the greatest public health successes, saving millions of lives worldwide from diseases such as meningitis to polio.
"By not vaccinating your child you run the risk of serious illness and death: why would parents choose that?"
What threat are measles currently?
Between January 1, 2018 and October 31, 2018, there were 913 confirmed cases in England.
This is compared to 259 cases in the whole of 2017.
The sharp increase is associated with outbreaks related to travel to Europe, especially among teenagers and young adults who missed their BMR vaccine when they were younger, according to the NHS.
The US currently has its largest outbreak in 25 years.
The worst hit city has been New York, in particular the Orthodox Jewish communities in Brooklyn, according to the American Centers for Disease Control and Prevention and Municipal Public Health Officers.
A similar outbreak occurred last year in the Orthodox Jewish areas of London, which are thought to be due to close communities.
The current outbreak in the US is also linked to travel from Ukraine, and in the last year there have also been outbreaks of measles in Europe and elsewhere.
Preliminary worldwide data from the World Health Organization show that the cases reported increased by 300% in the first three months of 2019 compared to the same period in 2018.