WHO says countries should stockpile H5N1 vaccine

The World Health Organization is about to advise countries to stockpile the influenza vaccine for H5N1, responsible for the deadly birdflu outbreak in Southeast Asia.

Canada is exempted from this strategy because it has already amassed stockpiles of two types of anti-viral drugs, has a long-term contract for made-in-Canada pandemic flu vaccine and the recent go-ahead to make, test and license trial batches of H5N1 vaccine. This project could reduce by four months the manufacturing time if that virus erupts into a pandemic. Canada already has a very good mixed package of different complementary interventions at its disposal.

The upcoming policy is meant to provide financial incentives for flu vaccine makers to start crucial work on developing and testing H5N1 vaccines.

The United States has ordered two million doses for stockpiling; France and Italy are in negotiations to buy bulk orders as well.

Dr Klaus Stohr (WHO) agrees with Canada's chief public health officer Dr. David Butler-Jones who does not support the idea of stockpiling H5N1 vaccine at this point in time. He prefers preparatory measures that protect against a wide array of pandemic possibilities - not ones that would be useful against one subtype of influenza but useless against another.It is better economics to finance research and develop infrastructure than produce a vaccine for a virus which is constantly changing and could be ineffective.

Influenza viruses mutate ceaselessly, and one year's flu shot may offer no protection the next year - or even limited protection in the year it was made. A vaccine made from a virus that was spreading in Vietnam in the spring of 2004 - the source of vaccines currently being made - might offer minimal protection if H5N1 sparks a pandemic in the spring of 2007. and it would be of no use if another subtype of influenza went on to trigger a pandemic instead.

WHO's advice that countries consider stockpiling H5N1 vaccine only makes sense for those that aren't laying in caches of anti-viral drugs, which will be the only real defence in the period from the start of a pandemic to when an effective vaccine becomes available. Anti-virals will work for every subtype and have a long shelf life. Production and storage costs, a short shelf life and the dilemma of who should get limited supplies of stockpiled vaccine and who would not are disadvantages, but if H5N1 starts a pandemic, stockpiled vaccine could be used as a "primer" in the initial stages.

It will take at least two doses of vaccine to develop a protective response to H5N1, a virus with which human immune systems have no experience. The stockpiled vaccine, while not a specific match to a pandemic strain, might kick-start the immune response and would speed the entire process of immunizing Canadians, potentially freeing up the country's vaccine manufacturer, ID Biomedical, to be able to export vaccine sooner to parts of the world where no flu vaccine production takes place.

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