澳门金沙城娱乐客户端:Swine flu update: When can we expect a vaccine?
By Debora MacKenzie It seems swine flu confusion is spreading almost as fast as the pandemic. What should pregnant women do? Who will be vaccinated, and when? Debora MacKenzie investigates. Are pregnant women at greater risk of infection, and if so, why? The US Centers for Disease Control and Prevention found that 8 per cent of the first 99 people who died from swine flu in the US were pregnant, and at the time of writing two of 29 deaths in the UK are known to have been pregnant or new mothers. About two per cent of women are pregnant at a given time. Women’s immune reactions are suppressed during pregnancy so they will not attack the genetically foreign fetus. This might explain why pregnant women seem to be slightly more vulnerable to the virus. The UK has advised pregnant women to avoid crowds where possible and unnecessary travel. When can we expect a vaccine? It’s not clear. The World Health Organization estimates that, by August, global production of the vaccine will reach 94.5 million doses per week. But this estimate relies on all companies using formulations with novel adjuvants – additives to the vaccine that boost the immune response and reduce the amount of virus needed for each dose. However, the adjuvants have not been approved for use in the US. Last week the US National Biodefense Science Board said that in order to have any vaccine available by September, the US should stick to the well-tested formulation of the seasonal flu vaccine – with 15 micrograms of the main viral protein, haemagglutinin, per dose. The WHO warns though that if adjuvants are not “fully used” the amount of vaccine available per week will fall by 40-50 per cent. Who will get the vaccine first? Again, it’s hard to come up with a clear answer. The US, UK and other governments have promised that people at greatest risk from the virus will be vaccinated first. But it is not yet known if this means people who are obese or pregnant – so far the clearest risk factors. More on these topics: