US authorities announced Thursday they have halted clinical trials of an experimental vaccine designed to halt the virus that leads to AIDS after discovering it did not stop infection. The program, which began in 2009, is the latest in a series of unsuccessful studies of candidate vaccines aimed at tackling HIV, the human immunodeficiency virus.

Bill Gates announced in Abu Dhabi on Thursday his foundation will contribute $1.8 billion to the Global Polio Eradication Initiative, a third of the total funds needed. "I am pleased to announce for the foundation that we are committed to fund a third of what is needed for this campaign," the Microsoft co-founder told the Global Vaccine Summit in Abu Dhabi. "So for the fully funded campaign, that would be $1.8 billion that we are committed to." "There has been a total of four billion dollars raised here. That gives us 73 percent of" the $5.5 billion needed, he said.

Police say gunmen shot to death a policeman protecting a team of female polio workers during a U.N.-backed vaccination campaign in a village of northwestern Pakistan. Police officer Mohammed Nabi Khan says another police officer was wounded in Wednesday's attack in the district of Mardan in Khyber Pakhtunkhwa province. He says no polio workers were harmed since they were inside a home giving polio drops to children at the time of the attack.

If a physician takes preventive health practices like getting a flu shot, his or her patients are more likely to undergo these preventive measures, a new study has found. The study, published in the Canadian Medical Association Journal earlier this week, found a consistent, positive relation between physicians' and patients' preventive health practices. In the study, researchers at Canada's University of British Columbia and in Israel looked at the screening and vaccination practices of 1,488 physicians and their almost 1.9 million adult patients in Israel's largest health care