Vaccination of medical staff and high-risk groups has started in a number of European countries. In the northern hemisphere, winter is approaching fast and the number of flu infections is on the rise. The United States is already in the grip of a flu epidemic; the Netherlands and a number of other European countries are approaching the epidemic phase.

The number of flu cases changes on a weekly basis. At this moment, the figures show a rising curve, but it is difficult to predict what will happen in the coming weeks, says Ab Osterhaus, virologist at Erasmus Medical Centre in Rotterdam.

Medical staff and high-risk groups can get a flu jab as of mid-November. Based on the seriousness and extent of the flu epidemic, the government may decide to extend the vaccination campaign to include the entire population or sell or donate the surplus vaccine to countries which have none. Last week, Health Minister Ab Klink said he was considering selling the surplus.