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.
For further information, please contact Mr Gregory Hartl, Spokesperson, WHO, Geneva,
telephone: (41 22) 791 4458, fax: 41 22 791 4858, e-mail: