Many parents remain unconvinced the MMR vaccination is safe, as illustrated by this week's appeal court ruling that two children must have the controversial jab, against their mothers' wishes. But, as Kate Watson-Smyth discovered, those who have opted for single injections are now finding there isn't enough vaccine to go round

The voice on the end of the phone was unequivocal: "There is no more mumps vaccine. We don't know when there will be, so you'll have to give him the MMR. It won't take long to arrange." I was stunned into silence. The "him" in question was my two-year-old son, Isaac, and the reason for my silence was that a year ago my husband and I had, in common with thousands of other parents, decided against the controversial MMR injection and opted instead for a lengthier but, we felt, safer course of single jabs.

Twelve months and £200 later, Isaac had been given his measles and rubella injections, and I had rung the private clinic that had administered them to make an appointment for mumps, the last remaining jab.

But it was not to be. The receptionist casually informed me that there was a global shortage of the single mumps vaccine, and that we were now one of around 10,000 MMR refusenik families left in limbo, two-thirds of the way through the course, by a system that stubbornly refuses to accommodate those who decline MMR for their children.

Like all those others, we had only tried to do the right thing for our child, while acting as socially responsible parents. At some length, we sifted the evidence for and against MMR and made our decision at the height of the MMR hysteria last summer, when it seemed that you couldn't open a newspaper or turn on the TV without being reminded of the controversy. But we were far from alone in our dilemma.

One friend agonised for weeks, booked an MMR jab, cancelled it, then rebooked and refused to discuss the matter further. "I've thought about it and decided - and I don't want to confuse myself again," she said at the time. Other parents in our social circle ended up going with the MMR, holding their noses and with their fingers crossed behind their backs. There have, as yet, been no adverse reactions.

Some parents reject vaccination altogether. Others, like ourselves, made alternative arrangements because we could afford to pay for a full course and, more to the point, we felt that we could be trusted to do so - one of the main objections to single injections so often cited by the Department of Health.

After several weeks of research, we chose a central London clinic that offered to administer the measles jab first. Isaac and his friend Conrad were taken together, we handed over our £90 and the job (or jab) was done.

The clinic's doctors recommended that we should wait a year before giving the next injection, but said that a minimum of six months would be fine. About eight months later, we rang to book the second jab. Most people choose to have mumps next, but since I and many of my friends were considering second pregnancies at that stage, it seemed sensible to get the rubella out of the way.

When I rang the clinic to arrange the rubella appointment, I asked about the availability of the mumps jabs, as I had heard rumours of a possible shortage. But I was assured that the clinic could get its hands on a plentiful supply and there would be no problem. So once again, Isaac and Conrad were taken together, we handed over our £90 and the job was done.

Earlier this week I rang the clinic once more to arrange the mumps jab and finally have the whole business out of the way. "Oh no, madam," came the voice on the other end of the phone. "We don't have any mumps vaccine - not until at least next year." After a long silence during which I couldn't seem to marshall any sort of comment, I asked if there was a waiting list, so that we could at least ensure that Isaac got his jab once fresh vaccine arrived in the country. "Oh no, madam," said the voice once more, "we can't run a waiting list - there would be about 7,000 names on it."

But how did this so-called global shortage of mumps vaccine come about? (There is apparently still plenty available to be used to make up one M of the MMR treatment). Should we be worried? Problems began last winter, when Merck, the US pharmaceuticals giant, decided to abandon manufacture of the strain of the vaccine that it had hitherto been supplying - Jeryl-Lynn I - and to make a better, more effective, strain, Jeryl-Lynn II. Then, Merck's German subsidiary, Chiron Behring, was forced to dump 250,000 doses of Mumpsvax after it was found to be faulty.

These events alone were sufficient to deplete supplies dramatically, but preparations for the war in Iraq had a more immediate and profound effect. While British troops headed for the Gulf were all given MMR jabs, some 45,000 US soldiers were administered the single mumps vaccine - a move that, at a stroke, reduced stocks to critical levels. Jeryl-Lynn II will not be available until towards the end of this year.

But because of the Department of Health's policy on single injections, even when the new strain is on the market it will take months to clear the backlog. This is because Jeryl-Lynn II is not licensed in Britain, which means that it cannot be provided on the NHS as it has not passed DoH tests on safety and effectiveness. Under such circumstances, only 25 doses per day can be brought into the UK - a figure set in the 1970s. It doesn't take a mathematical genius to see that it will take months to vaccinate every child who is waiting to be vaccinated against mumps.

And according to Direct Health 2000, a private company that has become a licensed importer of Mumpsvax (and that is confident of a regular supply come September), there has been no let-up in demand for single jabs from parents.

"We are still getting enquiries from people every day who don't want the MMR and who are happy to start a course of single jabs, even though they know there might be a long wait before they can finish it," said a spokesman.

"Of course, if you were prone to conspiracy theories, you might have to wonder why there is enough single vaccine for the American soldiers and enough to go in the MMR, but not enough for those who want to make alternative arrangements. This refusal by the Government to acknowledge the fact that people want single jabs and are going ahead with them, is simply forcing [parents] into a position of irresponsibility, through no fault of their own."

The Government's position is, of course, well known, and it won't be changing its mind any time soon. "The advice to parents has been, and remains, that MMR is the best option," said a Department of Health spokesman yesterday.

"And for those parents who have started a course of single jabs, the advice is that they should now have the MMR which, in our opinion, has always been the right thing to do." The spokesman went on to assure me that there was no problem administering MMR to a child who has already had one or two single jabs, but if I wasn't convinced by MMR before Isaac had had any vaccinations, I was hardly likely to change my mind now.

I decided to try to track down a single vaccine on my own. But it quickly became apparent how careful one needs to be. The Jeryl-Lynn strain is used in the MMR vaccine and widely recognised to be both safe and effective. If you decide to vaccinate your child abroad, you need to be sure that you are being offered that strain.

Naturally there are dozens of websites dedicated to MMR and its alternatives. On one bulletin board I found a message from a parent, saying that he had been offered a vial of the single mumps vaccine in a pharmacy in Switzerland, and that it was possible to bring it back to Britain if you could find someone to administer it. But the correspondent did not elaborate on what strain it was and how easy it had been simply to wander into a pharmacy and ask for the stuff. Other countries where it might be available include Belgium and Italy. In France, as in the UK, it is not licensed.

But Direct Health 2000 warns that parents must exercise extreme caution if they are offered any mumps vaccine in Britain or abroad. "The point is that there just isn't any of the Jeryl-Lynn around, so if someone says that they can get you some, our advice would be to steer clear," said the spokesman. "There is one strain called Urabe that has been linked to serious adverse reactions, and if you do find someone who is prepared to give your child this injection, you need to check the product information and make sure that it isn't this strain."

And so we await the arrival of the new vaccine. Isaac is on a waiting list at another clinic, although we have been warned not to expect a call even to tell us how long that waiting list is until November, and then it will be several months before he is finally vaccinated.

Are we being irresponsible by refusing to back down and give Isaac the MMR? Perhaps. Perhaps not. As our family doctor told us a year ago when we asked her advice: "They haven't proved that MMR is linked to autism, that's for sure. But they haven't proved that it isn't, either."