A drug company and a charitable foundation announced yesterday that they will launch a major campaign against trachoma, an eye infection that is one of the leading causes of preventable blindness in the world.

Pfizer Inc. and the Edna McConnell Clark Foundation will spend about $66 million in the next two years to treat and prevent the disease in five countries. Should the effort prove successful, it may be expanded to a dozen other countries where the disease is endemic, officials of the International Trachoma Initiative said.

The strategy includes distribution of antibiotics, promotion of personal hygiene, improvement of water supplies, and use of a relatively simple surgical procedure for severe cases. The program will begin in Morocco, Ghana, Mali, Tanzania and Vietnam.

Trachoma is caused by a form of the microorganism chlamydia. It is transmitted primarily between mothers and children, or between children, by hand-to-eye contact. About 150 million people are infected, and 3.2 million to 5.5 million -- most of them women -- are blind from the disease, primarily in Africa, parts of Southeast Asia and the Persian Gulf states of Oman and Yemen.

Clean water, combined with the habit of washing one's face and hands every day, eliminated trachoma in the United States and most other industrialized countries early this century. Where the disease remains, treatment consists of putting an ointment containing the antibiotic tetracycline in the eyes twice daily for six weeks. This is difficult to achieve, especially in children.

"The missing piece of the puzzle was a long-acting antibiotic," said Michael Bailin, president of the Clark Foundation, which began supporting research on a better trachoma treatment in the late 1980s. Since then, studies have shown that a single dose of the antibiotic azithromycin cures the infection.

Azithromycin is made by Pfizer and sold under the trade name Zithromax. It is the biggest-selling name-brand antibiotic in the United States. Worldwide, the company will sell about $1 billion worth of it this year.

Pfizer will provide enough doses to treat about 3 million people over the next two years and will contribute $3.5 million to the program. At a news conference here, a company executive, Lou Clemente, valued the contribution at $62 million and said it will be Pfizer's largest international philanthropic effort. The Clark Foundation will contribute about $3.5 million in the next two years.

A pilot project in two remote areas of southern Morocco reduced trachoma prevalence by about 40 percent in the past few years, said Jaouad Mahjour, an epidemiologist in the Moroccan ministry of health. In villages where more than 20 percent of the population is infected, all women and children are treated. In places with lower prevalence, treatment is more selective.

A single one-gram dose of azithromycin stays in the body for several weeks. The goal is to treat a population in a short period of time -- generally a month -- to interrupt transmission of the infection to the maximum extent possible, said Joe Feczko, a physician with Pfizer.

Trachoma causes blindness by scarring the upper eyelid, which eventually becomes deformed and curls inward. The eyelashes then abrade the cornea, scarring it and making it opaque. The program will train village nurses and other health workers to perform a 15-minute operation that can correct the eyelid deformity and prevent blindness.

Several officials of the initiative stressed, however, that medicine and surgery are only part of the strategy.

"Environmental improvements, such as better access to clean water, and education about the importance of face washing are just as important, if not more so, to the success of the program," Feczko said.

Research has shown public health campaigns can increase face and hand washing even in places with limited water supply. Pfizer and the Clark Foundation chose the five countries because they were committed to all the facets of the campaign.

"We wanted to be sure we had a program that worked, and that we weren't just handing out antibiotics in a nondisciplined fashion," Clemente said.

Pfizer is committed to donate the drug for only the next two years, but may extend or expand the program if it is successful.