Dr David Pugh runs a private clinic

The youngsters had all been given single jabs for measles, mumps or rubella at a private clinic run by Dr David Pugh in Elstree, Hertfordshire.

The same clinic offered the families blood tests after concerns that the batches of vaccine were unsafe.

It has left many parents unaware whether their children have been successfully inoculated for potentially serious diseases.

Concerns

Dr Pugh is among relatively few doctors prepared to give the single measles vaccine to parents.

He has vaccinated hundreds of children at his private Lifeline Care clinic at Elstree Aerodrome.

It was closed down several weeks ago by the National Care Standards Commission for not being properly registered.

Investigations began last month into claims vaccines prepared at the clinic were unsafe.

Measles outbreaks

The single measles vaccine is the only alternative to the triple MMR vaccine, though some doctors have cast doubt on its efficacy.

The single jab is not available on the NHS anywhere to younger children - it does not have a licence because many doctors believe it does not work well enough.

Measles remains a killer in the developing world, taking the lives of about one million children worldwide.

The number of cases in England and Wales has tripled in recent years and is at its highest since the MMR vaccine was introduced in 1988.