Three years after the UK was declared measles-free, cases of the disease have increased so much that the status has been withdrawn by the World Health Organization (WHO).

Prime Minister Boris Johnson has called for renewed efforts to meet 95% coverage targets for both doses of MMR. Currently only 87% of children receive the second dose of the vaccine.

Salud Pública Inglaterra is warning that an estimated one in seven 5-year-olds may not be up to date with their routine vaccinations, putting them at risk of catching serious diseases as they start primary school. In London, this figure could be as high as one in four.

Measles can be serious

Most children with measles are better within 7-10 days but complications can develop, especially in malnourished children or those with a poor immune system, such as those with el VIH o leucemia.

Many malnourished children around the world die when they get measles, usually from a secondary lung infection (neumonía). In the UK, there are still reports of unvaccinated children who die from measles complications.

A safe and effective Vacuna MMR which protects against measles, paperas y rubéola is usually given when a child turns one. A second booster dose is usually given to children before they start school at the same time as the Vacuna 6 en 1. Both doses are required for full protection against measles. If a dose of MMR is delayed for any reason, it can still be given at a later age. If necessary, the vaccine can be given at any age.

Around 30,000 (or more than 5%) of the 680,000 5-year-olds starting school this September have not received any MMR vaccine, putting them at a significantly higher risk of measles than children who have been fully protected.

90,000 5-year-olds still need to receive their second dose of the vaccine which is required for full protection. Uptake of other vaccines is also low, with around 100,000 or one in eight 5-year-olds having not received their 6-in-1 pre-school booster vaccine to protect against diphtheria, whooping cough, tétanos y polio.

In part, the reduced uptake of the vaccine has been attributed to a widespread belief that the measles risk is so low that it is not necessary to be vaccinated, according to Health Secretary Matt Hancock. "It's easy to forget how devastating measles can be precisely because vaccines are so effective at preventing it in the first place."

Other explanations for the drop include ongoing myths about vaccination, and anti-vaccination campaigners and organisations spreading misinformation to parents.

Dr Mary Ramsay, head of immunisation at Public Health England, stressed the importance of herd immunisation and boosting uptake of the vaccine for those who are eligible. "Elimination can only be sustained by maintaining and improving coverage of the MMR vaccine. Measles is one of the most infectious diseases known to man - only one person travelling back to an area with lower vaccination rates can lead to an outbreak. Anyone who has not received two doses of MMR vaccine is always at risk.”