By Clare Murphy
Health reporter, BBC News
It is peak season for chickenpox - the highly-contagious, blistering virus which for most children is unpleasant and for a very few lethal. A safe and effective vaccine is available - why don't we use it?
Chickenpox - for most mild but unpleasant
The varicella vaccine is available privately, but the UK's immunisation body decided last year against universal vaccination of children - as carried out in many developed countries - citing cost and the fear it could increase shingles, a reactivation of the virus, in older people.
Yet while a vaccine against shingles for the elderly may now be in the offing, removing at least one of the potential hurdles, all debates about childhood vaccines still take place under the shadow of the upset over the measles, mumps and rubella jab (MMR), sparked by a now discredited research paper over a decade ago.
Despite international confirmation of its safety, a small number of parents still refuse to give their child the jab - and many in the medical community believe this explains the reluctance of the authorities to introduce a brand new injection into the childhood immunisation schedule.
"This is what it's really all about," says Professor Adam Finn, consultant in paediatric infectious diseases at Bristol Royal Hospital for Children.
"The fact is parents who should be able to protect their child against chickenpox, an entirely preventable, unpleasant disease, are being held hostage by a small minority.
"Chickenpox is a disease which stops children going to school, means parents have to take time off work, and for children who are already sick can be very severe. And for a small cost we could be rid of it."
Like the wind
Chickenpox is not referred to in medical literature before the 17th Century but it is thought to be an ancient condition whose name springs from the fact that the blisters resemble chick peas.
Cases of the disease are not recorded in this country, but they are thought to number about 600,000 a year, and by the age of 12 some 90% of us will have had it. There is speculation that it may be rising among the very young as increasing numbers attend nurseries where they are more likely to pick up infections.
When compared to what were once the other common illnesses of childhood, it is less serious than measles, for instance, but potentially more problematic than mumps.
Caused by the varicella zoster virus
Spreads through the air and direct contact with fluid from blisters
Spots usually appear two-three weeks after contact
Thought to number 600,000 cases per year
Once infected, may return as shingles in later life
In healthy children, serious complications are not common, but in rare cases it can lead to septic shock as a result of the blisters becoming infected, as well as pneumonia and encephalitis.
In those children whose immune systems are compromised - those with leukaemia, for example - chickenpox can be a real problem. Half of these youngsters develop complications and some of those die.
Doctors can immunise as soon as a condition like leukaemia is diagnosed, but this is not risk free nor always effective.
And for pregnant mothers and their unborn babies, chickenpox can in extreme cases lead to foetal deformities - hence the warning in maternity wards for the infected to stay away.
Apart from the costs of hospitalisation, there are also the economic implications of parents taking sometimes weeks off work to care for back-to-back infections among siblings who are barred from schools and nurseries.
Germany introduced a vaccination programme against what it calls windpox, due to the speed with which it spreads, in 2004 after a study concluded that paying for vaccination out of the public pot would be more than compensated by fewer sickness payments to absent parents in the longer term.
It followed the lead of Japan and the US, which were among the first nations to introduce universal vaccination back in the 1980s and 90s.
And so far, the jury is still out on whether a chickenpox vaccine would indeed increase the incidence of shingles, a reactivation of the dormant virus which can cause severe and persistent pain in adults.
Shingles can cause long-term excruciating pain in the elderly
The theory is that once a person has had chickenpox, every time they come into contact with an infected youngster their body's defence system receives the equivalent of a booster jab, building up resistance against the disease.
If children no longer harboured the disease, a rise in shingles could in principle follow - although the data from countries where the chickenpox vaccine is established has yet to produce compelling evidence of this.
The UK's immunisation committee - the JCVI - has in any event recommended that the over-70s be vaccinated against shingles, a programme which could come into effect by the end of the year.
This does not alleviate the reservations of Nigel Scott from the Shingles Support Society.
"In an ideal world we would vaccinate everyone over 50 against shingles and then go ahead with the childhood chickenpox vaccine, but we are not there yet. If we live till 85, half of us will get shingles, and for some people this can be very serious indeed - some describe the pain as absolutely unendurable.
"Let's not forget that when parents have to take time off for their young children, increasingly adult children may have to take time off to care for sick, ageing parents."
As for expense, the JCVI says in the "short term" the costs would outweigh the benefits.
There are also priorities. Experts say a vaccine against another form of meningitis is likely to be given preference over chickenpox in the immediate future.
All talk of new vaccines takes place against a backdrop of MMR uptake rates which while resuming, still fall below those needed to confer immunity on the community.
The Lancet, the medical journal which published the original research linking MMR to autism in 1998, last month published a full retraction, while the General Medical Council ruled in January that Dr Andrew Wakefield, who suggested the link, acted "dishonestly and irresponsibly" in the course of his work.
"But I don't think we can say it's yet consigned to history, sadly," says Dr David Elliman, immunisation expert at the the Royal College of Paediatrics and Child Health (RCPCH).
"The chickenpox vaccine is definitely desirable, and I think it it will happen, but unfortunately I don't think we are ready for the debate yet - not until we get MMR rates back where they need to be. We need to win that one first."