16 February 2001
EXPERTS DECIDE CONTENT OF 2001-2002"NORTHERN HEMISPHERE" INFLUENZA VACCINE
The composition of the vaccine for year 2001-2002 (Northern 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 Geneva, Switzerland this week. The experts recommended that the influenza vaccine for 2001-2002 (Northern Hemisphere) contain the following three components:
Between October 2000 and February 2001, mild to moderate influenza activity was reported throughout the world. Influenza A(H1N1), A(H3N2) and B viruses continued to be isolated in the southern hemisphere, mainly from sporadic cases. In the northern hemisphere, influenza activity was initially reported during the third week of November, increased in December and continued through February.
Influenza activity was mainly due to influenza A(H1N1) virus, which co-circulated with influenza B viruses in some countries. Influenza A(H3N2) viruses were isolated sporadically. In most countries, the greatest impact was in children and young adults.
WHO strongly recommends the use of vaccine as an effective preventive measure against this potentially fatal disease. About 50% to 80% of vaccine recipients will be protected against the disease when there is 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 infected with or 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.
All WHO recommendations are published in WHO’s Weekly Epidemiological Record (WER) and 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 Reference and Research on Influenza in Atlanta (USA), London (UK), Melbourne (Australia) and Tokyo (Japan). 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.
Recommendations for the composition of vaccines intended for May 2002 to October 2002 (southern hemisphere) will be made by WHO in September 2001. The timing of WHO's recommendations is critical to allow sufficient time for companies to produce the vaccine before the new influenza season starts.
For more detailed information on influenza, including a history of major outbreaks, please see WHO Fact Sheet N° 211 (http://www.who.int/inf-fs/en/fact211.html).
For further information please contact Gregory Hartl, WHO Spokesperson, Geneva, telephone: (+41 22) 791 4458, fax: (+41 22) 791 4858. E-mail:firstname.lastname@example.org All WHO Press Releases, Fact Sheets and Features can be obtained on Internet on the WHO home page http://www.who.ch