Experts meeting over the past two days at the World Health Organization (WHO) on advances in pandemic influenza vaccine development reported encouraging progress.

According to a WHO press release, sixteen manufacturers from 10 countries are developing prototype pandemic influenza vaccines against H5N1 avian influenza virus. Five of them are also involved in the development of vaccines against other avian viruses (H9N2, H5N2, and H5N3).

At present, more then 40 clinical trials have been completed or are ongoing. Most of them have focused on healthy adults. Some companies, after completing safety analyses in adults, have initiated clinical trials in the elderly and in children. All vaccines were safe and well tolerated in all age groups tested.

For the first time, results presented at the meeting have convincingly demonstrated that vaccination with newly developed avian influenza vaccines can bring about a potentially protective immune response against strains of H5N1 virus found in a variety of geographical locations. Some of the vaccines work with low doses of antigen, which means that significantly more vaccine doses can be available in case of a pandemic.

These developments were discussed at the WHO meeting on the evaluation of pandemic influenza prototype vaccines in clinical trials that took place in Geneva, Switzerland, on 15-16 February 2007. This was a third such meeting in just two years and its objectives were to review progress in the development of candidate vaccines against pandemic influenza viruses and to reach consensus on future priority activities.

More than 100 influenza vaccine experts-from academia, national and regional public health institutions, the pharmaceutical industry and regulatory bodies throughout the world-attended the meeting convened by the WHO Initiative for Vaccine Research and the WHO Global Influenza Programme. Information on more than 20 projects was presented and discussed. Most manufacturers are using reference vaccine strains corresponding to H5N1 viruses provided from by WHO Collaborating Centres.

In spite of the encouraging progress noted at the WHO meeting, WHO stresses that the world still lacks the manufacturing capacity to meet potential global pandemic influenza vaccine demand as current capacity is estimated at less than 400 million doses per year of trivalent seasonal influenza vaccine.

In response to this challenge, WHO launched in 2006 the Global pandemic influenza action plan (GAP) to increase vaccine supply, a US$10 billion effort over 10 years. One of its aims is to enable developing countries to establish their own influenza vaccine production facilities through transfer of technology, providing them with the most sustainable and reliable response to the threat of pandemic influenza. WHO is currently working with several vaccine producers, mainly in developing countries affected by H5N1, to facilitate establishment of in-country influenza vaccine production.