A shortage of measles-mumps-rubella vaccine has forced Britain to prioritise supplies for routine childhood immunization, at the expense of catch-up campaigns for thousands of teenagers and young adults born before the vaccine was introduced, it was learned on Friday.

Immunisation experts warned the move - disclosed in letter from the Department of Health’s immunisation team - is a step backwards for public health and would risk a further surge in mumps - already up tenfold in the past year.

The letter, leaked to Pulse magazine, states: “In the last three months, we have issued six months worth of stock of MMR. Some of this increase has been for routine immunisation as coverage is beginning to increase.

“However the majority has been used to respond to mumps outbreaks and for other catch-up activities. As a consequence, our MMR stocks are currently extremely low. Supplies have been prioritised for routine childhood immunisation.”

The letter, dated April 13th, states that additional stocks of MMR have been ordered but advises that local immunisation campaigns should not be publicised until “you receive confirmation from the Department that supplies of vaccine are available. Hopefully, we will not have to impose these supply restrictions for very long.”

A Health Department spokeswoman told APM the aim of the letter was to prioritise MMR for young children because the complications are more severe in this age group than in teenagers and young adults.

However, Pulse said general practitioners were outraged at the latest supply crisis, after also suffering shortages in flu vaccine over winter. Some doctors had to cancel clinics and others were being asked to share their MMR stocks.

Dr. George Kassianos, immunisation spokesperson at the Royal College of General Practitioners told the magazine: “They (the government) should never ask GPs to embark on a campaign if they can’t guarantee enough vaccine. GPs are left with young candidates for immunisation but no vaccine to administer.”

Dr. Mohammed Abid, immunisation coordinator for Berkshire and consultant in communicable disease control, said: “I have never seen so many cases of mumps. We are really worried. It’s a step backwards for public health.”

Phil Johnson, Editor of Pulse, said: “GPs have been offering MMR to as many young people as possible in an attempt to stem the rise in mumps, with many taking part in coordinated catch-up campaigns. It seems extraordinary that the Government failed to anticipate the pressure this would put on vaccine stocks. It is enormously frustrating for GPs and damaging to the public’s health.”