An Ebola vaccine test conducted in Kenya has shown it can protect people against the infection without causing side-effects.

Initial results from the Phase 1 trials of the candidate Ebola vaccine rVSV-ZEBOV released by the Kenya Medical Research Institute (Kemri) suggest that the vaccine is safe, and that it generates an immune response.

The candidate vaccine was given to 138 volunteer nurses and clinicians across four sites in Kilifi on Kenya’s Coast. No serious side effects were seen among them. Some experienced fever in the first few days after vaccination, while others developed transient pain and/or swelling of their joints.

“Health workers were chosen to participate in the vaccine trials because they have been proven to be extremely at risk of the viral attack,” said Benjamin Tsofa a policy researcher at Kemri’s, Wellcome Trust Research Programme.

Dr Tsofa said that Kenya and Gabon were selected in Africa for the vaccine trials because they are low-risk countries for an Ebola attack.

“The initial trials could not be conducted in West Africa because the region already has a full blown Ebola outbreak,” said Dr Tsofa.

He said that Kenya, Malawi, Gambia and Gabon are classified among the countries in Africa with the right capacity and infrastructure to conduct a study of this nature.

The research study was also carried out in Switzerland and Germany.

In Kenya, the trials started in January after receiving approval from the country’s ethics body, the Pharmacy and Poisons Board.

The project benefited from a $5 million grant from the Wellcome Trust, which allowed several global partners, overseen by the WHO, to gather essential safety data for rVSV-ZEBOV. The candidate vaccine had been tested only in monkeys prior to the Ebola outbreak in West Africa.

According to the vaccine’s initial results published in the New England Journal of Medicine, a single dose of the Canadian-made rVSV-ZEBOV is safe and effective in producing antibodies that ward off the Ebola virus.

Although there are no cases of Ebola reported in Kenya, the fact that the vaccine has demonstrated safety and immune responses in the Kenyan population is useful information to facilitate its use.

It is, however, not yet clear whether the vaccine can prevent a person from becoming infected with Ebola.

Offer protection

“The vaccine is safe and has potential to offer protection against Ebola. The vaccine will be tested further in the countries affected by Ebola,” said Solomon Mpoke, director of Kemri.

In Guinea, some 10,000 people will receive an injection of rVSV-ZEBOV in a massive clinical trial being conducted by the government and international partners, including the WHO. The patients will be followed for three months and the results could be available as early as July.

“You cannot test a vaccine for Ebola if there’s no Ebola,” said Charlie Weller at the Wellcome Trust in the UK, which has provided about $20 million in funding for vaccines, treatment and research. “You need an active epidemic, which is why there has been such a global collaborative effort to start these (vaccine) trials as quickly as possible.”

To date, the WHO has identified two vaccines as being most advanced: rVSV-ZEBOV first developed by researchers at Winnipeg’s National Microbiology Laboratory in Canada; and chAd3-ZEBOV, developed by the US National Institute of Allergy and Infectious Diseases (NIAID), and pharmaceutical company GSK.

The vaccine candidate, chAd3 - ZEBOZ uses a chimpanzee-derived cold virus to deliver the Ebola virus genetic material from the Zaire strain of the virus that caused the outbreak in Liberia.

The other candidate — rVSV-ZEBOV being tested in Kenya — employs vesicular stomatitis virus, an animal virus that primarily affects cattle, to carry an Ebola virus gene segment.

Tests in Liberia

Both leading Ebola vaccines are being tested in Liberia in trials that began in February. Volunteers are assigned at random to receive a single injection of chAd3-ZEBOV, the rVSV-ZEBOV vaccine or a placebo.

A recent study by US scientists warned that the Ebola outbreaks could become more likely due to climate change and human encroachment into untouched natural habitats.

The scientists said that there will be an increase in the outbreaks because people are moving around more, the contact between humans and the wild is on the rise, and possibly because of climate change.

Some experts suspect that population pressure and deforestation in Sierra Leone, Liberia and Guinea, which have brought people into closer contact with wild animal hosts of numerous viruses combined with changes to rainfall patterns that affected the numbers and behaviour of bats, may have led to the first transmission of Ebola in West Africa, a region that prior to last year had never had an outbreak.

Sierra Leone, Liberia and Guinea, the three West African countries hardest hit by Ebola, have set a target of having no new cases by the end of this month.
WHO data shows that the outbreak has killed more than 10,000 people in the three countries over the past year.