Use of the experimental vaccine, known as rVSV-ZEBOV, will now spread to the more rural regions of Iboko and Bikoro where the majority of cases have occurred.
Vaccination began in the urban setting of Mbandaka to "prevent an urban outbreak" as well as further spread along the nearby Congo river, to reduce "risk through the interior of DRC and surrounding countries," Dr. Peter Salama, the deputy director-general of the World Health Organization's Health Emergencies Program said Tuesday.
He confirmed the outbreak spread to Mbandaka after two brothers visited Bikoro to attend a funeral and traveled back to the city.
"Mbandaka is relatively safeguarded at the moment," he said, adding that officials "haven't seen an explosive increase in cases" and the teams have reason to "cautiously optimistic."
There have been 54 cases of Ebola reported in Congo, including 25 deaths. Thirty-five of those case have been confirmed with laboratory tests.
Salama said 47 of the cases were in the more rural regions of Bikoro and Iboko where control efforts will now be focused. "That's where the next phase of vaccination must go."
The vaccine is proving to be a very acceptable intervention to the community in Mbandaka, Salama said. "There are no reports of refusal of the vaccination."
"Over 90% of eligible people are getting vaccinated," said Dr. Michael Ryan, WHO assistant director-general for Emergency Preparedness and Response, highlighting that this is a strong coverage rate for any vaccine.
More than 900 contacts are being followed in Congo, and the number is likely to increase.
The Ebola vaccine being provided has been shown to be safe in humans and highly effective against the Ebola virus, according to the WHO. A 2016 study
found it to be 100% effective in trials in Guinea in coordination with the country's Ministry of Health after the 2014-15 outbreak.
Therapeutics to be tried
Five experimental drugs to treat Ebola virus disease, including ZMapp and Remdesivir, have now arrived in the country and will be trialed under strict experimental research protocols, Salama said.
This means they will have to be used as part of a clinical trial, with ethical review and informed patient consent.
Officials expect to get formal approval for delivery in the coming days.
HO officials hope to introduce the life-saving therapies to patients, but their use will require sophisticated monitoring. Some of the treatments require IV infusion, while others require daily assessment of liver and kidney function, according to Ryan.
In 2014, ZMapp became known when it was used to treat two American missionary workers, Dr. Kent Brantly and Nancy Writebol, who contracted Ebola in Liberia. Prior to that, the experimental drug had been tested only in monkeys.
This is "not a simple effort to do this kind of trial in this kind of environment," said Salama. But "if we don't learn now we'll never know which drugs to use in this situation."
Vaccination, therapeutic and control efforts have and will be carried out through partnerships between WHO, the International Federation of the Red Cross and Red Crescent Societies, Medecins sans Frontieres (Doctors Without Borders) and many other NGOs on the ground in Congo.
Control efforts will expand to four more provinces considered to be at risk, the IFRC confirmed.
Ebola virus disease, which most commonly affects people and nonhuman primates such as monkeys, gorillas and chimpanzees, is caused by one of five Ebola viruses. On average, about 50% of people who become ill with Ebola die.
The first human outbreaks of Ebola occurred in 1976, one in the north of what is now Congo and in the region that is now South Sudan.
Humans can be infected by other humans if they come in contact with bodily fluids from an infected person or contaminated objects from infected persons. Humans can also be exposed to the virus, for example, by butchering infected animals.
West Africa experienced the largest recorded outbreak of Ebola over a two-year period beginning in March 2014; a total of 28,616 confirmed, probable and suspected cases were reported in Guinea, Liberia and Sierra Leone, with 11,310 deaths, according to the WHO.