The BBC's Jane Bolger reports

Sense, the National Deafblind and Rubella Association, has warned that a refusal to use the combined vaccine could lead to an increase in the number of children born with severe disabilities.

However, Andrew McCoig, a pharmacist in Croydon, Surrey took the decision to import single jabs to address parents fears about side-effects from the combined MMR jab.

The individual vaccines are not licensed for use in the UK.

The MMR jab immunises children against measles, mumps and rubella.

But fears that the combined injection could have dangerous side-effects has led some parents to not have their children immunised at all.

Research findings

Evidence published in The Lancet medical journal suggests that the combined jab may cause autism and Crohn's disease.

Autism is a neurological disorder that affects the functioning of the brain and Crohn's disease affects the bowels.

The BBC's Dr Rosemary Leonard: "The risk is far less than the risk of the disease itself"

However, the link is not proven and doctors place the risk of side-effects from the combined jab at less than 0.001%.

They say that the damage the diseases themselves can inflict is far greater than the risk posed by the combined vaccine.

Rubella, for example, can induce congenital rubella syndrome (CRS), which can cause babies to be born both deaf and blind, and in some cases with heart and brain impairments.

Sense has warned that refusals to take the combined vaccination could lead to a resurgence of CRS.

Swiss imports

Mr McCoig has started importing individual vaccines from Switzerland to offer aprents a choice.

Andrew McCoig is importing single vaccines

Although they are not licensed for use in the UK, GPs can prescribe them on a "named-patient" basis. This means the GP becomes personally responsible for the outcome of the treatment.

Mr McCoig said: "I believe that parents should be able to exercise a choice about their child's immunisation."

At the moment the combined jab is the only licensed vaccine because the Department of health sees it as the most effective, both in clinical and cost terms.

Parental fears

But parents fear that the impact of three vaccines - weakened forms of the actual diseases - in one go is too much for a young child.

Michael and Terry Thomas had the combined jab at 15 months. They both now suffer from autism and bowel disease and their mother represents 2,000 parents who believe the vaccine has damaged their children.

Mrs Thomas says that when Michael, who had it first, reacted badly to the injection, she was told that it "was only a virus, a coincidence".

When Terry had a similar reaction, she says, "I put two and two together - that it was to do with the MMR".

Slim risk

Doctors point out that the link is unproven, and say that the link could be purely coincidental, as autism is usually detected around the same time as the MMR vaccine is administered.

Dr George Kassianos: "Trust in the vaccine"

GP Dr George Kassianos said: "Parents should be able to trust the MMR vaccine.

"If they don't have their children vaccinated, we will go back to the time when the measles infection was circulating in the community, with all the devastating effects that could have on our children and babies."

Sense said the MMR was "clinically the most effective way to protect children" and attacked the importation of individual vaccines.

Malcolm Matthews, the association's director of policy and national services, said: "While we believe parents should make choices about their child's health care, there is no evidence that single vaccines are preferable."

He said that single vaccines led to a greater risk of children getting any of the three diseases, as there was no guarantee that they would complete the course of three injections.

Children were also vulnerable between immunisations, he said, and warned that a move away from combined vaccinations could have dire consequences.

"If the downward trend in people being vaccinated continues, there could be another outbreak of rubella with all the misery and devastation that can cause," he said.