3rd WHO meeting on evaluation of pandemic influenza prototype vaccines in clinical trials, 15-16 February 2007, WHO, Geneva
Summary and meeting documents
Vaccines are the most important intervention for prevention of pandemic however, at present they are not existent and considerable research programme should be carried out to accelerate availability of effective pandemic vaccine. At present, 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, N5N2, and H5N3). 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 elderly and in children.
On 15-16 February 2007, WHO Initiative for Vaccine Research and Global Influenza Programme convened a meeting to review evaluation of H5N1 pandemic influenza vaccines in clinical trials and recommend on research to accelerate availability of effective pandemic vaccines. This was a third such meeting in just two years. 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 where the iinformation on more than 20 projects was presented and discussed. Most manufacturers are using reference vaccine strains corresponding to H5N1 viruses provided from by WHO Collaborative Centres.
All vaccines tested to date were safe and well tolerated in all age groups. Most of the data were obtained on the healthy adults and further studies in children, the elderly or immunosuppressed individuals are warranted. Whole virus preparations appear to be more immunogenic than equivalent doses of split vaccine. Alum adjuvanted split vaccines, a striking contrast to some of the more promising alum adjuvanted whole virion vaccines, show modest increases in immunogenicity over unadjuvanted vaccines, but not sufficient to allow significant dose sparing. Some split vaccines formulated with newer adjuvants show encouraging immunogenicity which will probably allow dose sparing. Several manufacturers have established formulations which they believe will meet regulatory requirements and will submitting applications for licensing this year. Some studies demonstrate that vaccination with currently available H5N1 prototype vaccines was able to induce a potentially protective immune response against highly pathogenic strains of H5N1 virus isolated at different times in a variety of geographical locations. Because of the inherent variability in the assay systems used to measure immune responses, it is unwise to directly compare results from different studies.