11.   Possible new vaccine fights malaria throughout its life cycle.

12.   The drug is not the first possible vaccine to go into human trials.

13.   The first large-scale testing of a possible vaccine began last week.

14.   The National Institute of Allergy and Infectious Diseases, the biggest vaccine backer, is financing two dozen different possible vaccines.

15.   Given these difficulties, specialists have had to weigh the ethical dilemmas in undertaking human trials of possible vaccines.