One of Pakistan’s most crucial public health campaigns has been plunged into crisis after militants killed eight volunteers over the course of a three-day polio vaccination drive.img width='1' height='1' src='http://rss.nytimes.com/c/34625/f/640346/s/26cc2f5a/mf.gif' border='0'/br/br/a href="http://da.feedsportal.com/r/151883606148/u/0/f/640346/c/34625/s/26cc2f5a/a2.htm"img src="http://da.feedsportal.com/r/151883606148/u/0/f/640346/c/34625/s/26cc2f5a/a2.img" border="0"//aimg width="1" height="1" src="http://pi.feedsportal.com/r/151883606148/u/0/f/640346/c/34625/s/26cc2f5a/a2t.img" border="0"/