Health officials yesterday launched an impassioned defence of the decision to introduce a five-in-one vaccine for babies from the age of two months. The head of the Government's immunisation programme insisted that the new jab was safe and warned that any boycott by parents could lead to the re-emergence of potentially-fatal diseases such as whooping cough.

Health officials yesterday launched an impassioned defence of the decision to introduce a five-in-one vaccine for babies from the age of two months. The head of the Government's immunisation programme insisted that the new jab was safe and warned that any boycott by parents could lead to the re-emergence of potentially-fatal diseases such as whooping cough.

There are fears that another damaging health scare, similar to that surrounding the MMR vaccine, could emerge around the five-in-one jab for polio, diphtheria, tetanus, whooping cough and Hib (Influenza B).

The news that the new vaccine will be introduced from next month was leaked by a Department of Health official on Friday, five days before the Health minister, John Hutton, had planned to tell GPs, health professionals and the media.

Anti-vaccine campaigners spent the weekend claiming that the new jab could overload the immune system of young babies and cause developmental problems. They also said that the fact that the polio component of the new vaccine does not contain any mercury-based preservatives, unlike the current jab, proved that mercury (which has been linked to autism) was dangerous and did harm youngsters.

David Salisbury, head of immunisations at the Department of Health, returned on Sunday from a holiday to find that what he thought would be seen as an improvement in the vaccination programme was mired in controversy and confusion.

Yesterday, he and the Department of Health went on the attack, backed by international research and the support of experts, to avert an MMR-style slump in immunisation uptake. Dr Salisbury said: "This vaccine is safe and effective and parents should get their children immunised, just as they always have done.

"If you do not get your child immunised, they will be at risk of things like whooping cough, and these are diseases that can and do kill."

He said the main reason for switching from the triple jab, containing diphtheria, tetanus and pertussis (whooping cough) to the five-in-one vaccine was that the virtual eradication of polio meant that Britain could now move to a new, safer form of immunisation.

Currently, children are immunised with a live oral polio virus which contains mercury. The oral polio vaccine (OPV) is highly effective and is still used in countries where the disease is prevalent because it not only immunises people but can stop any infection that does occur from spreading. But in rare cases the OPV can itself cause the disease. Most recently, there were two cases in England and Wales in 1998.

With the disease eradicated from Britain and disappearing from the rest of the world, the Government's Joint Committee on Vaccination and Immunisation (JCVI) has deemed it safe to move to the inactivated polio virus (IPV) jab used in most western countries.

While there is a global initiative to reduce any unnecessary environmental exposure to mercury and other metals, international research has concluded that there is no link between the type of mercury found in vaccines (thiomersal) and any disorders or health problems among children,

Dr Salisbury said the decision to switch to the new vaccine was based entirely on the world situation regarding polio and that the move to mercury-free jabs was merely a consequence rather than a "driver".

Another reason for the introduction of the jab was that it contains a version of the pertussis vaccine which causes fewer adverse reactions in children. Around half of babies given the current pertussis vaccine, which contains the entire whooping cough organism, suffer from sore arms and an increase in temperature in the 48 hours after they are immunised.

The new version is inactivated and only 35 per cent of children have any reaction. Experts say the new jab, made by Aventis Pasteur, is actually safer because it contains fewer live viruses and could be even more effective in preventing disease.

Dr Salisbury said: "There are fewer ingredients in the new vaccine. There are fewer immune challenges - not more." The five-in-one jab is used in Canada, where more than 3.5 million doses have been given to children and studies have shown it to be safe.

Dr Salisbury also hit out at those lobby groups who claim to be experts and at renegade researchers, who he said were publishing ill-founded studies that claimed to prove a link between vaccines and childhood disorders such as autism.

He said: "Some of these experts are anything but, and it is very difficult for parents to know who to listen to."

Philip Minor, head of virology at the National Institute for Biological Standards and Control, said: "This new vaccine is really good news and I do not understand how the message has become so confused."

Anti-vaccine groups yesterday continued to refuse to accept the assurances of the medical community,

Jackie Fletcher, founder of JABS (Justice, Awareness, Basic Support) said: "Increasing the combinations increases the potential for an adverse reaction and restricts choice for parents. I am concerned that we do not end up in another situation like MMR."

PARENTS' AND DOCTORS' VIEWS

MARILYN SMITH from Harrow, mother of Daniel, 11, and Gabriella, 7

I totally disagree with this - I'm appalled. These tiny babies have undeveloped immune systems. No child of mine would have five vaccines in one go. Daniel had his MMR when he was 12 months old and lost all his hair. I'm convinced it was from his injection, and that changed my mind about vaccines. Afterwards I felt I'd just gone along with it all without thinking much about it. So with Gabriella I weighed up the pros and cons and delayed her having any jabs until she was 15 months - it wasn't worth the risk. Do they really need these injections that early? If they're a bit older, their system has a better chance to cope with it.

DR GILLIAN BRAUNOLD GP in Kilburn, north London

We as a society have signed up to immunisation and we want to protect our children from dying unnecessarily from diseases we can prevent. All we're talking about here is continuing improvements in standards; that's what this new vaccination will do. It's much better if the polio vaccine is no longer in a separate, active vaccine, when there remains a small risk you can catch polio if you change a nappy and aren't protected yourself. And removing the mercury-based element is another step forward. But there's been a failure to release information in an orderly and managed fashion.

DR TERRY JOHN GP in Walthamstow, east London, and member of British Medical Association's GP's committee

It seems to me [five-in-one] is a neat and tidy way of doing things [but] it was predictable there would be some kind of worry about overloading children with vaccines. More should have been done by the Department of Health to prepare for it. The communications system is appalling for professionals who are not given advance warning of these stories before they blow up, and then have to advise the public. Why don't the powers-that-be let healthcare professionals know what is going on? By the time the DoH machinery gets into gear, it will be too late because people will already have made up their mind.

KATE HOWIE member of the RCN Practice Nurses' Association national committee, and practice nurse trainer for Northamptonshire PCT

The vaccine is a good idea, because you're getting rid of the live polio and popping it all into one vaccine; it brings the chances of contracting polio down to virtually nil. And there's no mercury in this one.

But it really does need to be handled quite smartly, because there are going to be a lot of anxious parents over the launch of this five-in-one. We're inundated with queries from anxious parents, and the Government needs to make sure we have the information to pass on. The phone calls this morning from parents were continuous.