Who to vaccinate? Experts in the dark whether the young and healthy or elderly aremost at risk

But even knowing who is vulnerable is a problem, experts say.

Historically, during seasonal flu epidemics, priority has gone to the elderly and those with chronic diseases, such as asthma or other lung conditions.

"But we know from our research that it is actually younger populations which are more affected during pandemics - it is one of the signature features of pandemics," Miller told AFP.

SHOOT: There is also a lot of debate whether a vaccine does more harm than good. A vaccine can also teach this virus to raise its game and become deadlier. No one is thinking about that of course.

clipped from www.news24.com Paris - Northern hemisphere countries have so far ordered more than one billion doses of swine flu vaccine, the World Health Organisation said on Tuesday, sparking warnings over shortages. Some countries - notably Greece, The Netherlands, Canada and Israel - have ordered enough double doses to inoculate their entire populations. Others, such as Germany, the United States, Britain and France, have put in orders that would cover between 30 and 78% of people. "Pandemic vaccine orders put in by northern hemisphere countries stand at over one billion," WHO spokesperson Melinda Henry told AFP. Intense demand coupled with production delays could create shortages, forcing governments that are preparing for a second, possibly more deadly, wave of flu to make hard choices about who to vaccinate first, experts have warned. A shortfall in supply would essentially oblige national health authorities to ration the vaccine.