二十多年來，科學(xué)家們一直努力研制預(yù)防艾滋病毒感染的疫苗。最近的一次失敗發(fā)生于去年九月份。研究人員中止了藥品公司默克的兩項(xiàng)實(shí)驗(yàn)艾滋疫苗研究?！?/div>
The report says prevention programs can be effective if governments invest at least thirty cents a year per person.For more than twenty years, scientists have been trying to develop a vaccine to prevent H.I.V. infection. The latest failures came last September. Researchers halted two s…