The world is at risk of the worst outbreak of measles for decades due to the coronavirus pandemic.

More than 100 million children are set to miss out on their measles vaccines this year due to lockdown designed to stop deaths from COVID-19, according to the World Health Organisation.

More than 6,500 children have already died from the disease in the Democratic Republic of Congo.

Measles cases were already on course to reach a twenty-year high this year.

The WHO calls for tracking of all children who miss out on the vaccine.

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The world is at risk of a surge in measles deaths, with around 117 million children set to miss out on their measles vaccine this year due to the international coronavirus lockdown, according to the World Health Organisation.

Measles vaccine programmes have already been halted in 24 countries since the coronavirus pandemic began, the WHO said in a statement on Tuesday.

The halt to vaccine programmes, which the WHO expects to soon be extended to 13 more countries, comes after a recent international resurgence in the disease.

"Despite having a safe and effective vaccine for over 50 years, measles cases surged over recent years and claimed more than 140,000 lives in 2018, mostly of children and babies – all of which were preventable," the organisation said in a statement.

"Against this already dangerous backdrop, preventive and responsive measles vaccination campaigns have now been paused or postponed in 24 countries to help avert further spread of COVID-19."

The global chief of immunization at Unicef, Dr Robin Nandy, told the Telegraph last month that the UN agency has paused its vaccination programmes because of concerns about increasing the spread of the coronavirus.

"We do not want to contribute to the COVID problem through immunization programmes, so we are recommending that all campaigns are temporarily suspended as they bring a lot of people together. We don't want to do any harm" he said.

He added, "It would be inappropriate for us to recommend a campaign when the government is ordering a shut down as it would be impossible to conduct it at the right time."

The WHO had aimed to eliminate measles altogether in Europe by 2020. However, the disease has made a resurgence in recent years due to slow vaccination rates.

Some countries have seen a recent spike in deaths from the disease.

In the Democratic Republic of Congo, more than 6,500 children have already died from the disease, with international deaths expected to reach a 20-year high Nature reported last week.

The WHO have called on governments to implement tracking programmes of all children who miss out on vaccines due to the coronavirus pandemic.

"If the difficult choice to pause vaccination is made due to the spread of COVID-19, we urge leaders to intensify efforts to track unvaccinated children, so that the most vulnerable populations can be provided with measles vaccines as soon as it becomes possible to do so," the organisation said on Tuesday.

"While we know there will be many demands on health systems and frontline workers during and beyond the threat of COVID-19, delivering all immunization services, including measles vaccines, is essential to saving lives that would otherwise be lost to vaccine-preventable diseases."