In a major boost to a UN campaign to eradicate an eye infection that causes blindness, Pfizer has announced that it will provide a free antibiotic to treat about 90 percent of the 150 million people afflicted.

　　The international organization leading the fight against trachoma-related blindness said it is "enthusiastic" that with the medicine it can now achieve the goal set by the World Health Organization of eliminating the ancient scourge by 2020.

　　Over the last five years, the pharmaceutical giant has provided 8 million doses of the antibiotic Zithromax to the International Trachoma Initiative to treat sufferers in nine impoverished countries in Africa and Asia.

　　Hank McKinnell, Pfizer's chairman and chief executive officer, told a news conference on Tuesday that the initial program had been so successful that Pfizer would donate 135 million additional doses of Zithromax - which he called "the gold standard for fighting trachoma" - over the next five years."That represents a 15-fold increase and the largest donation of a patented medicine in history," he said.

　　Zithromax is an antibiotic that is used primarily to treat respiratory tract infections in children. It has over US billion in worldwide sales annually, McKinnell said.

　　McKinnell said the 8 million doses, plus other support to the initiative from Pfizer over the last five years, was worth about US million in wholesale prices in the countriesswheresZithromax was distributed.

　　He refused to put an estimate on the value of the 135 million additional doses, saying "preserving someone's sight is priceless." But another executive said it was "many hundreds of millions" of dollars.

　　Serge Reznikoff of the World Health Organization called the Pfizer announcement "very exciting and promising."

　　Over the past century, trachoma was eliminated in many countries, including virtually all of the Americas, Europe and Australia. In the early 1900s, infected immigrants were barred from entering the United States and trachoma was a major public health concern until it was eradicated half a century ago.

　　But it is still prevalent in 48 countries in the poorest parts of Africa, Asia and Latin Americaswheresclean water and sanitation are scarce.

　　Trachoma is caused by the bacterium Chlamydia trachomatis which can be spread easily by hands, clothing, or flies that have comesintoscontact with discharges from the eyes or nose of an infected person. Over time, it results in turned-in eyelashes which then scratch and scar the cornea, leading to blindness if not treated.