Each year, the World Health Organization (WHO) Global Influenza Programme convenes meetings to analyse the global data on circulating influenza virus strains and make recommendations for the vaccine to be used for the coming influenza season. WHO also provides the vaccine manufacturing industry with prototype strains for the seasonal vaccine as well as materials to ensure and validate that global vaccine standards are met.

This year, more than 10 000 influenza viruses from all continents were isolated and characterized by the WHO/National Influenza Centres. These laboratories, which are located in more than 80 countries, form the backbone of the global influenza surveillance programme. Based on that assembled information, WHO today published its recommendations on the formulation of the influenza vaccine for the Northern Hemisphere.

This year´s analysis, which concluded yesterday, was conducted by members of the WHO Collaborating Centres on Influenza and has recommended that vaccines to be used in the 2005-2006 season (Northern Hemisphere) should contain the following:

• an A/New Caledonia/20/99(H1N1)-like virus
• an A/California/7/2004(H3N2)-like virus^a
• a B/Shanghai/361/2002-like virus^b

These recommendations are used by pharmaceutical manufacturers to update the composition of the influenza vaccines they produce. This annual adjustment is necessary to match the vaccine with the changing viruses expected to be circulating during the coming influenza season.

Recommendations for the composition of the vaccine to be used in the Southern Hemisphere will be made at a meeting in September.

While influenza vaccine coverage has improved significantly in the last ten years, the vaccine is not reaching everyone in the high risk categories. These categories, defined by WHO, include the elderly, those who are at increased risk because they have other respiratory or cardiovascular disease, and health care workers. However, influenza vaccine use in developing countries remains minimal to nonexistent.

Last year, WHO´s Member States set a goal of 60% coverage for those in these high risk groups, and 75% coverage by 2010.

Since young children can develop severe disease, some countries have also started including vaccination of children as part of their national influenza policy. Vaccinating children may not only reduce their disease burden but it may also reduce transmission to the elderly and others at increased risk.

The current influenza season is now approaching its peak. All elderly persons or those with a particular risk of influenza should be vaccinated.