The flu vaccine: a high-stakes gamble

Paris

IT is a high-stakes gamble with thousands of human lives on the line. Yet twice a year, every year, the UN's World Health Organization (WHO) bets on the flu - which virus types are likely to dominate in the coming season? On this basis, a vaccine is prepared months in advance.

"We cannot say for sure which virus will be circulating," Wenqing Zhang, head of the WHO's global influenza programme, said. "What we're doing is based on the best possible surveillance information and analysis, and basically to bet, or to project, what viruses will likely be circulating."