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Poor antigen yields limiting H1N1 vaccine supplies, says WHO

Published on 15/07/09 at 11:32am

Inadequate production capacity means that the poorest countries in the world will be denied access to vaccines for H1N1 influenza, according to the World Health Organization.

To compensate for the shortfall, the WHO's Strategic Advisory Group of Experts (SAGE) has issued a series of recommendation aimed at eking out scant supplies, including prioritising vaccinations for healthcare workers, pregnant women and patients with chronic medical conditions.

"Since the spread of the pandemic virus is considered unstoppable, vaccine will be needed in all countries," said WHO director-general Margaret Chan, who described the manufacturing capacity for vaccines as "woefully inadequate."

One of the problems faced by the vaccine makers is that the seed strains used in manufacturing are not producing much of the haemagglutinin antigen that forms the basis of the inactivated vaccine. At the moment yields are between 25% and 50% of the normal yields seen with seasonal flu strains, according to WHO's Marie-Paule Kieny.

"In order to remedy that the WHO laboratory network is trying to generate new vaccine [strains] from wild type virus isolated from patients," she told a press conference.

An existing donation agreement with two vaccine companies - Sanofi Pasteur and GlaxoSmithKline - will supply 150 million doses of H1N1 vaccine to developing countries, and while this is welcome it is "obviously not enough", Chan told delegates attending a World Intellectual Property Organisation conference in Geneva, Switzerland, yesterday.

With much of the already-limited capacity already earmarked for distribution to affluent countries around the world, she said the WHO was negotiating with vaccine producers to boost supplies for poorer nations.

In the last couple of days, the US ordered $690 million-worth of bulk antigen and adjuvant used to make swine flu vaccine from Novartis and a further $71 million-worth of adjuvant from GlaxoSmithKline. It also placed a $61.4 million order for antigen from Sanofi Pasteur, while AstraZeneca's MedImmune subsidiary received a second order worth $61 million for its live attenuated nasal spray vaccine.

Meanwhile, Germany's government agreed to place an order for 50 million additional doses, enough to vaccinate 25 million people. The country says that with the latest order it will have enough vaccine to protect a third of its 82 million inhabitants.

In its meeting on Monday, the SAGE also concluded that there was, so far, no concern of the safety of vaccine using new adjuvants, but that it was 'urgent' to collect safety data in groups for which this is not yet available.

The panel added that as production of seasonal influenza vaccine in the northern hemisphere was close to completion, there was no need to recommend a switch from seasonal to H1N1 vaccine.

The swine flu outbreak was upgraded by the WHO to full pandemic status last month and by July 6 had affected nearly 100,000 people worldwide and claimed around 500 lives.

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