viernes, mayo 01, 2009

There’s no such thing as a simple flu jab

By Vivienne Parry (THE TIMES, 27/04/09):

The first question on people’s lips when the spectre of pandemic flu looms large is often: “Is there a vaccine and where can I get it?” That question is no doubt being asked again now with the outbreak of swine flu in Mexico.

Flu is an awesome foe because it is so slippery, constantly changing its colours. Every year the World Health Organisation decides which strains are likely to be most prevalent in the following year and bases the annual flu vaccinations on this combination.

Many assume that H5N1 will be the pandemic flu sub-type and that it will emerge from the Far East. Indeed, some pharmaceutical manufacturers are banking on it. GlaxoSmithKline, for instance, it has committed $2 billion to conduct research and expand capacity for its its antiviral drug Relenza, along with a new H5N1 vaccine, which was given marketing authorisation in all 27 EU member states a year ago. But the truth is that pandemic flu could arise from another strain altogether, from an entirely different quarter of the world. Like Mexico for instance.

The GSK product and a number of those from other manufacturers are generic, not specific H5N1 vaccines. They do not offer full immunity but are likely to reduce symptoms and deaths. The UK is currently stockpiling 3.3 million doses, which, in the event of an outbreak, are likely to be given first to frontline healthcare workers.

To produce a vaccine for a specific pandemic the exact strain has to be isolated and “tamed” so that it is safe for manufacture. From isolation to first shot in an arm takes at least 20 weeks - just for the first batches. By the time there is enough for the entire British population the outbreak could be over. Hence Britain’s strategy to stockpile the generic vaccine in addition to putting plans in place for specific ones.

Biological manufacture is not like manufacturing cars. Flu vaccines are difficult to produce. Most are grown in eggs - one vaccine shot, one egg. It requires huge flocks of birds. If manufacturers focus on specific strains there is no capacity for regular flu treatments, which means that in the UK up to 25,000 more winter deaths would occur.

The dangers of overreacting to a flu pandemic are well known to the Centres for Disease Control in Atlanta. In January 1976 an 18-year-old American army recruit, Private David Lewis, collapsed after an all-night training exercise. He died a few hours later in the base hospital of Fort Dix, New Jersey. Like about 300 other recruits he had complained of typical flu symptoms but Private Lewis had ignored the medical officer’s orders to go to bed and went off on his exercise.

His death was caused by a previously unknown variant of swine flu A/H1N1. What really spooked the CDC was its similarity to the strain that killed more than 40 million people worldwide in 1918.

The CDC rightly decided to develop a swine flu vaccine for use in the following flu season. Despite careful planning, the national influenza vaccination programme went wrong from the outset. Two doses of vaccine were expected from each egg used, but only one materialised, setting back the timetable dramatically. Then doctors discovered that the vaccine doses that worked well for adults did not protect children effectively. At this point there were only four million doses for 57 million children.

Just as the programme seemed dead on its feet an outbreak of fatal pneumonia broke out at the Pennsylvania Convention of the American Legion, killing 29 people. This was later identified as Legionnaire’s disease, hence its name. The media linked it with swine flu and politicians joined in the clamour to push forward the swine flu vaccination programme.

The threat from swine flu was vastly exaggerated, so that eventually the President, Gerald Ford, took charge. A mass vaccination went ahead even after it became clear that swine flu was not a danger. In fact, Private Lewis was the only person to die from a mere 300 cases. The programme cost more than $200 million and as a side-effect there were thousands more regular flu deaths because of a lack of vaccine.

Another rare and fatal side-effect occured in about nine in every million of those vaccinated, who developed Guillain Barré Syndrome, a paralytic disease. When so many are involved, rarities become numerous. There were 500 cases and 25 deaths from GBS. The vaccination programme was stopped, having only treated 24 per cent of the population. And because the US Government had indemnified the vaccine manufacturers before the programme began (because American insurers wouldn’t take on the risk) they had to pay out an additional £39 million in compensation claims.

The point is not that mass vaccination is wrong. Far from it. But vaccination has to be carefully considered. The risks have to be clearly balanced against the benefits, decisions have to be taken on the science not the politics and frequently re-evaluated. For the one thing that will never change is flu’s capacity to surprise us.

Fuente: Bitácora Almendrón. Tribuna Libre © Miguel Moliné Escalona

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