Measles cases are likely to spread rapidly unless more people get vaccinated, the UK Health Security Agency says.

More than four million parents, carers and young adults are being contacted to tell them that they or their children have missed out on one or both doses.

Measles is a highly contagious disease which is spread by coughs and sneezes.

Common symptoms include:

Small white spots may appear inside the mouth.

A blotchy red or brown rash usually appears after a few days, typically on the face and behind the ears before spreading to the rest of the body.

Measles normally clears up after seven to 10 days. However, complications can include pneumonia, meningitis, blindness, and seizures.

Babies and young children, pregnant women and those with a weakened immune system are more at risk.

Measles can be fatal, but this is rare. Between 2000 and 2022, 23 children and adults died as a result of measles or related infections.

Anyone of any age can catch measles.

If you catch it while pregnant, the disease can lead to stillbirth, miscarriage or your baby being born small.

That is why the NHS is urging young adults to make sure they have had both doses of the MMR vaccine before they think about starting a family.

It is possible, but highly unlikely.

The body builds up immunity to the disease after being infected the first time.

The vaccine is very effective. After two doses of the MMR vaccine, 99% of people will be protected against measles and rubella, and 88% will be protected against mumps.

The first MMR dose is usually given at 12 months and the second at about three years and four months.

However, you can catch up on the jabs at any point, whether you are a child or an adult.

You can speak to your GP surgery to book jabs for your child, or if you think you have missed your own vaccinations.

Pop-up clinics are being set up at some schools.

People who do not eat pork products can request an alternative version called Priorix.

If the MMR vaccine is not suitable, a treatment called human normal immunoglobulin (HNIG) can be given to someone at immediate risk of catching measles.

Most side effects are mild and do not last long.

The area where the needle goes in can be red, sore and swollen for a few days.

Babies and young children may develop a high temperature for up to 72 hours.

There is no evidence linking the MMR vaccine with autism.

Researcher Andrew Wakefield wrongly claimed the two were connected in 1998. His work was later dismissed, and Mr Wakefield was struck off by the General Medical Council in 2010.

At the time the claims were made, many parents chose not to have their children vaccinated. Those children are now young adults and being urged to get vaccinated.

The number of young primary school children who have had the MMR vaccine is below World Health Organization targets.

That makes outbreaks of measles much more common.

Some 85% of children in 2022-23 had received two MMR doses by the time they were five years old, the lowest level since 2010-11. The goal is 95%.

The West Midlands, particularly Birming