No one said tracking the movements of a patient, suspected to be a carrier of the deadly Ebola virus, through the dense forests of the eastern region of the Democratic Republic of Congo (DRC) was going to be easy.
With no discernible roads, only dense bush, we were forced to travel on three motorbikes to get to our destination, riding through areas where no car could reach.
There were six of us: a research investigator, a medical doctor, an officer monitoring water, sanitation, safety and security and the three motorbike drivers. After almost three hours we finally found our destination: a village in the middle of the forest. This was Bokongo.
It took our epidemiologist several days to find this remote village. He was tracing the travels and contacts of just one patient suspected of having Ebola. Just before the epidemiologist broke his leg, he identified some contacts and first line workers that needed to receive the Ebola vaccine.
After arriving in Bokongo we managed to vaccinate 13 first line workers. But ours was not the only operation.
As health authorities in the Democratic Republic of Congo continue to try and contain the Ebola outbreak in the north eastern region of the country, there are several teams vaccinating targeted populations in Bikoro, Ikoko-Impenge, Itipo, Mbandaka and Iboko.
The country's health ministry has stepped in to coordinate the response to the outbreak. And the World Health Organization, Médecins Sans Frontières, Epicentre and others organisations have sent teams of specialists to assist.
As a result more than 1500 people have been vaccinated so far. But already 27 people have died since the outbreak was declared on May 8, 2018. Ours is a race against time - making sure we get to everyone who could possibly be infected before the deadly virus does.
Part of the team
It's not the first time that I have been part of an Ebola response. As the African representative of Epicentre - the research arm of Médecins Sans Frontières - I have been involved in Ebola response since 2012 during the Kibaale outbreak in Uganda.
At the time I led Epicentre's Mbarara Research Centre. Then I coordinated the field and laboratory part of the clinical trial assessing vaccine's efficacy, safety and performance on first line workers in Guinea during the Ebola outbreak in 2014 to 2015.
The vaccine was also considered during the 2017 outbreak in Likati in the DRC. But the Likati Ebola outbreak ended with a limited number of cases and the vaccine didn't have to be used.
With the current outbreak in the DRC I came to the capital city, Kinshasa, two days after the outbreak was officially declared to assess the situation and see whether or not the vaccine could be part of the response.
The increasing number of cases and the fact that the outbreak had reached an urban area (Mbandaka) meant it was clear that the vaccine would be an additional tool for the response.
Testing a new vaccine
The vaccination is administered using a "ring" approach. This involves identifying newly diagnosed and laboratory confirmed Ebola patients. Epidemiologists first need to locate the people they have been in contact with. And then the patients and their contacts --- often family members, neighbours, colleagues and friends --- constitute the ring who all get vaccinated. First line workers from the health area where an Ebola case has been detected also qualify to receive the vaccine.
This method of investigating contacts is one of the biggest challenges when administering the vaccine. Tracing and following people to the middle of the forest presents a massive logistic challenge - which means that it can take days to find people who need the vaccine most.
The Ebola vaccine is known as a recombinant vaccine. This means that the glycoprotein of the Ebola virus has replaced the glycoprotein of another virus. The glycoprotein is important because it builds antibodies against a virus. Ebola's glycoprotein was added to the vesicular stomatitis virus, which is not harmful to humans. People are given the vaccination so that they can immediately build antibodies against the Ebola virus.
The vaccine was discovered by a small Canadian company and later bought by the big pharmaceutical company Merck. The vaccine is still not licensed but it's known as VP920.
Several studies across the US, Switzerland, Gabon and Kenya have assessed the safety of the vaccine which targets the Zaire strain of the Ebola virus.
Its safety, efficacy and immunogenicity was also assessed during the Ebola outbreak in West Africa in 2014; the results have shown great safety efficacy and effectiveness. The vaccine is still in the process of being registered - but this is a really long procedure.
One of my primary responsibilities has been ensuring that the teams that administer the vaccine have everything we need in this process. I've also coordinated our activities with health officials, the WHO and the country's extended programme for immunisation so that they understand how the vaccine is administered.
To launch the vaccine in this outbreak we've had to train the locally recruited staff about Ebola, the study protocol as well as good clinical practices. This includes ensuring everyone who gets the vaccine consents to it, understands the study and possible side effects.
This has been difficult because we only have a limited time to teach people about the dangers of the virus as well as the importance of the protocols when they are out in the field.
While the WHO team started administering the vaccine in Mbandaka, the MSF/Epicentre team went in Bikoro where all the confirmed cases from Itipo - the epicentre of the outbreak - were referred.
Since then vaccination drives have not stopped. Each time we enter a village we're greeted by one of the most frightening moments knowing that we're surrounded by people who have been in contact with the deadly virus but may not have been traced. But then we look into the eyes of the people full of hope and we're reminded about why we do what we do: to make a difference by reaching the unreachable.
Yap Boum, Mbarara University of Science and Technology