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Monday, 2 December, 2002, 18:28 GMT
Q&A: Smallpox vaccine
The UK government is publishing plans on how it might cope with a bioterror attack involving smallpox.

These include the vaccination of small numbers of military and medical specialists who would swing into action in the event of biological attack.

Mass vaccination of the population at large is not an option so far in the plans.

However, in the US authorites have said that a vaccine will be made available to anybody who wants it.

What is smallpox?

Smallpox is caused by the variola virus.

This comes in two strains: the less severe variola minor and the more deadly variola major.

It is highly infectious, and has an incubation period of between seven and 17 days.

Then symptoms such as headache, delerium and vomiting emerge, followed the development of the trademark rash.

It kills approximately one in three of those infected.

The disease was eradicated in its natural form after a global mass vaccination campaign.

However, it still exists in laboratory conditions and there are fears that it could have been obtained by terrorists and could be used in an attack.

What is the government doing about this?

The government signed a multi-million pound contract with the company Powderject earlier this year to provide enough smallpox vaccine for 20m people.

They have stocked up on a strain of vaccine - known as the Lister strain - which has been used in the UK since the 1960s.

The vaccine contains live vaccinia virus, which is closely related to the variola virus, the agent that causes smallpox.

If the doses are divided, in theory many more people could be vaccinated.

Who is to get the vaccination?

Key health workers, such as doctors and nurses, will be the offered the vaccine first.

Also offered the vaccine will be small groups of key military personnel.

However, in the event of a biological attack - which ministers still believe is highly unlikely - mass vaccination would still be possible.

It is likely that the population in the area immediately surrounding an attack location would be immunised first, rather than every man, woman and child.

Are there any risks?

Some people could not be vaccinated because there is a higher risk of severe, perhaps even life-threatening complications.

These people include pregnant women, people with immune system problems such as HIV, and people with eczema.

Every vaccination carries a small risk of adverse reactions, and a tiny number of these would prove fatal.

A study in the US suggested that if more than 80m people under the age of 30 were vaccinated, the likely number of deaths would approach 200.

So, before embarking on any mass vaccination campaign, public health experts would have to be convinced that the threat posed by a smallpox attack outweighed the likely cost in lives caused by vaccination.

Would the vaccine definitely work?

No vaccine can offer a 100% guarantee of protection against an infection.

The debate over the smallpox vaccine is further complicated by claims from the US that a vaccine against the Lister strain, such as the one ordered by the UK government, might not be the best option.

While the Lister vaccine has proved highly effective at eradicating naturally-occurring smallpox infections across the world, there is the suggestion that it might not work as well against so-called "battlefield strains" of the disease.

Why does the government face criticism?

The government is also under fire because the contract for the vaccine was awarded to UK company Powderject without a public tendering process and followed a 100,000 donation by its chief executive to the Labour Party.

Government scientists, however, feel sure that the Lister vaccine will provide sufficient protection against any other strain.

What is happening in the US?

The US government is stocking up with another type of vaccine developed by the New York City Board of Health to counter a strain thought likely to be the one used in a terrorist strike.

They believe that the Lister strain may be ineffective against the type of smallpox likely to be used in a terrorist strike.

President Bush has decided to make the vaccine available to all US citizens, beginning with the military and health workers who would be front-line defenders against a bioterror attack.

Experts at the US Centers for Disease Control and Prevention estimate that the country should have 280m doses of vaccine - enough for everyone - available by the end of the year.

See also:

30 Jul 02 | Health
07 Jul 02 | Americas
24 Sep 01 | Science/Nature
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