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Beginning in February, Liberia, Guinea and Sierra Leone will be host to trials sponsored by various government and non-governmental organizations.

LIBERIA

Estimated start date: Early February

Number of participants: 27,000 or more

Trial type: Liberia will play host to a randomized control trial with three groups and two Ebola vaccines. The tentative plan is to vaccinate 27,000 people in three equal-sized groups, although that figure may increase if the number of cases in Liberia continues to decline. The trial could even be expanded to Sierra Leone to make up for the dearth of Liberians at risk of contracting Ebola, senior officials from the U.S. National Institutes of Health have said. One of the three groups will receive the Canadian-made vaccine being developed by the drug companies NewLink and Merck, one will receive a vaccine developed by pharmaceutical company GSK and the NIH's National Institute of Allergy and Infectious Diseases, and the third group will receive a placebo. Researchers will then watch over nine months to a year to see how many people in each group contract Ebola. The first doses of both vaccines have already been shipped to Liberia.

Trial sponsor: The U.S. National Institutes of Health and the government of Liberia

GUINEA

Estimated start date: Late February

Number of participants: 9,500 or more

Trial type: There will be two types of trials in Guinea. One will be a simple observational study in which health care workers and other front-line staff are vaccinated and then monitored primarily for whether the vaccine is safe and produces an immune response. The second and larger of the two will involve a ring-vaccination strategy, the same approach that helped eradicate smallpox. Whenever an Ebola case is confirmed, researchers will swoop in and try to vaccinate as many of the patient's family members, friends and neighbours as possible to prevent the onward spread of the virus. Marie-Paule Kieny, the senior WHO official who is co-ordinating efforts to test experimental Ebola vaccines and treatments, said the plan is to vaccinate about 9,500 people through the ring strategy, half of them immediately after an infected person is identified, half of them three to four weeks later. The vaccine for this trial has not yet been selected, but the Canadian-made product is one of two in the running.

Trial sponsor: A consortium of non-governmental organizations, universities and governments, including the Public Health Agency of Canada, led by the WHO.

SIERRA LEONE

Estimated start date: Late February

Number of participants: 6,000 or more

Trial type: Sierra Leone is expected to host a "stepped-wedge, cluster-randomized" trial starting with health care workers and other front-line staff around Ebola treatment units or other health care facilities. The researchers will vaccinate groups at each health centre, one by one, over 18 weeks. "The idea is to see whether there is a difference in the number of cases in the group which has been immunized in the beginning as compared to the group which has been immunized late," Dr. Kieny of the WHO said. As in Guinea, only one vaccine candidate will be tested in Sierra Leone. The VSV-ZEBOV vaccine developed at the National Microbiology Laboratory in Winnipeg is one of two leading possibilities.

Trial sponsor: U.S. Centers for Disease Control and Prevention and the government of Sierra Leone

By the numbers:

GUINEA

117: Confirmed new cases, Sept. 22-28

30: Confirmed new cases, Jan. 19-25

2,917: Total cases confirmed, suspected, probable

1,910: Total deaths

LIBERIA

311: Confirmed new cases, Sept. 22-28

4: Confirmed new cases, Jan. 19-25

8,622: Total cases confirmed, suspected, probable

3,686: Total deaths

SIERRA LEONE

350: Confirmed new cases, Sept. 22-28

65: Confirmed new cases, Jan. 19-25

10,518: Total cases confirmed, suspected, probable

2,199: Total deaths

Source: World Health Organization as of Jan. 25, 2015

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