The composition of the vaccine for year 2001 (southern hemisphere influenza season) has been decided and communicated to vaccine manufacturers by the World Health Organization (WHO), following agreement on its content by international experts at a WHO meeting held in Crete, Greece. The experts recommended that the influenza vaccine for 2001 (Southern Hemisphere) contain the following three components:

WHO holds a Consultation each September to formulate a recommendation for the composition of inactivated influenza vaccines intended for the following southern hemisphere winter (May to September of the following year). The timing of WHO's recommendations is critical to allow sufficient time for companies to produce the vaccine before the new influenza season starts.

WHO strongly recommends the use of vaccine as an effective preventive measure against this potentially fatal disease (see WHO Weekly Epidemiological Record, No. 35, 1 September 2000, p. 281-288). About 50% to 80% of vaccine recipients will be protected against the disease when there is a good match between the vaccine and strains of influenza virus that are in circulation. In cases where the vaccine does not fully protect against the disease, severity of illness and the frequency of serious complications are reduced.

Most of the population has been previously exposed to influenza A(H3N2), influenza A(H1N1) and influenza B viruses and is known to have some degree of residual immunity. As a consequence, one dose of influenza vaccine should be sufficient for all ages except young children. Previously-unimmunized children should receive two doses of vaccine with an interval of at least four weeks.

The specific vaccine viruses used in each country should be approved by the national control authorities. National public health authorities are responsible for recommendations regarding the use of vaccines.

The justification for the 2001 vaccine composition recommendations will be published in WHO's Weekly Epidemiological Record (WER) in the 13 October 2000 issue and thus, communicated to public health authorities, national control authorities and influenza vaccine manufacturers.

The detection of new influenza viruses is made possible through the WHO network for influenza surveillance and control composed of 110 National Influenza Centres in 82 countries and the four WHO Collaborating Centres for Virus Reference and Research in Australia, Japan, the United Kingdom and the United States of America. This network helps WHO monitor influenza activity in all regions of the world and ensures that virus isolates and information are sent rapidly to the WHO Collaborating Centres for Virus Reference and Research for immediate strain identification.