A vaccine that could help protect medical workers as they fight Ebola in West Africa, even in the minutes after an accidental infection, may take at least a month to be available as global officials weigh its safety.

The sudden donation of as many as 1,000 doses of a vaccine that hasn’t been tested in humans is creating a conundrum because they could go to healthy people, rather than those already infected. Earlier, the World Health Organization decided that people in West Africa should be allowed access to promising experimental treatments or vaccines.

“I would personally not hesitate to take that vaccine,” said Thomas Geisbert, a virologist at the University of Texas Medical Branch and a developer of the vaccine donated to WHO by the Canadian government. “I’ve seen it used in many, many non- human primates. Never saw a problem with it.”

The WHO will review data on the vaccine’s design and results from animal studies to assess its safety, said Marie- Paule Kieny, the assistant director-general for health systems and innovation. It would then discuss which countries would get the doses, and in what quantities, she said.

All of that may take at least a month, Kieny said. “We cannot just take any vial of anything and start distributing it,” she said in an e-mail.

While the WHO studies the product, Canada will keep the donated doses in Winnipeg, where the vaccine was developed, Shelly Glover, Minister of Canadian Heritage and Official Languages, said in a news conference with reporters.

“In the meantime, they remain here in Winnipeg ready to go at a moment’s notice,” Glover said.

The calculations are being made as the disease has killed more than 1,000 people and teams of researchers rush to get their vaccines into clinical trials. The outbreak, the worst since the virus was first identified in 1976, has raged through Sierra Leone, Liberia and Guinea and recently reached Nigeria, Africa’s most populous nation. Modupeh Cole, a prominent Sierra Leone doctor treating Ebola patients, died after being infected with the virus, the government reported yesterday.

Renewed focus on vaccines was sparked by the donation of 800 to 1,000 vials to the WHO by the Canadian government. The vaccine, called VSV-EBOV, was developed by the Canada’s National Microbiology Laboratory and is licensed by Ames, Iowa-based NewLink Genetics Corp.

While vaccines normally are preventatives, the VSV-EBOV vaccine has shown effectiveness in studies on animals after they were exposed to the virus. It may be used soon after someone was exposed to infection, similar to the way rabies shots are used now, said Gary Kobinger, chief of special pathogens for the Public Health Agency of Canada.

Besides VSV-EBOV, there are four other vaccine candidates being developed with support from the U.S. National Institutes of Health, the most advanced which is being developed in conjunction with London-based GlaxoSmithKline Plc. The vaccines work by delivering benign Ebola genes into the body in such a way that they stimulate an immune response that will protect a person against future infection.

Glaxo’s candidate and VSV-EBOV are aiming to begin human clinical trials for safety by the end of September.

Glaxo is “talking to regulators and the World Health Organization to see what we can do to accelerate the process” of testing the vaccine, Catherine Hartley, a company spokeswoman, in a telephone interview. “Until we know it is safe, it is very hard to think about how and when and who it might be used for.”

The trial with Glaxo’s vaccine will enroll 20 healthy adults, Jennifer Routh, an NIH spokeswoman, said in an e-mail.

NewLink, a partner with Canada, is also working “around the clock” to start trials, president Nicholas Vahanian said in a telephone interview.

The company reserved enough of the vaccine for trials and made a joint decision with the Canadian government to donate the rest, Vahanian said. Trials will probably take place in multiple sites, including the U.S., he said. NewLink’s trial will have 39 people, according to Brian Wiley, vice president of business management.

NewLink also is negotiating with its manufacturers to ramp up production, aiming for 10,000 doses within months, Wiley said in a phone interview.

Some researchers are calling for officials to slow down and wait for safety trials to be completed.

Safety trials with vaccines are essential because “if something goes wrong with a vaccine, you have harmed a healthy individual,” said John Eldridge, chief scientific officer for Profectus BioSciences Inc., based in Baltimore.

Profectus also has an experimental Ebola vaccine that can completely protect monkeys from the virus, which could be in clinical trials in a year, he said.

It would be risky to perform initial safety trials of a Ebola vaccine in Africa where patients may be far from a good hospital that can provide modern medical care should something go wrong, said Hildegund Ertl, a professor of immunology at The Wistar Institute in Philadelphia.

“You need a safety trial in a country where you have easy access to health care before you go into rural Africa,” she said.

During an outbreak it would probably be difficult to conduct a controlled trial in which some people got a placebo and others a vaccine. The lack of such a trial means scientists are unlikely to get an unambiguous answer to the question of how well a vaccine works, she said.

Health workers on the front lines would be the ideal audience for a vaccine, as they may be in a better position to understand the risks of an unproven drug and reap any benefits, said G. Kevin Donovan, director of the Pellegrino Center for Clinical Bioethics at Georgetown University.

“It’s ethically a more tolerable situation in that health- care workers are presumably more medically sophisticated and understand the risks and benefits,” he said in a telephone interview.

Since the vaccine doses being donated by Canada are being considered for compassionate use, it means the use “will likely be limited to post-exposure,” which means “it would ideally have to be administered within 24 or 48 hours of a person being exposed to Ebola virus,” a spokeswoman for Doctors Without Borders said in an e-mail.

The non-profit organization has 676 staff members working in Guinea, Sierra Leone and Liberia.

There is no cure for Ebola. The virus has killed 1,069 of 1,975 people afflicted in the four West African nations as of Aug. 11, the WHO said yesterday.

The disease is normally treated by keeping patients hydrated, replacing lost blood and using antibiotics to fight opportunistic infections. The hope is that a patient’s immune system will eventually fight off the virus’s aggressive attack.

Nancy Kass, a professor of bioethics and public health at the John Hopkins Berman Institute of Bioethics in Baltimore, is among those urging a gradual roll out for the Canadian vaccine.

“If there was a some crazy side effect in 24 hours, you’d hate to think that 50 people were vaccinated in one day,” she said.