Scientists at the University of Oxford who were behind the AstraZeneca Covid-19 vaccine have launched a phase 1 trial to test a new vaccine against plague. Centuries after causing one of the worst pandemics in history, the infectious disease (sometimes referred to as “Black Death” or pestilence) continues to afflict parts of Africa, which today accounts for 90% of all reported cases.
Though plague can be successfully treated with antibiotics, there is no vaccine for the disease, and it is still endemic in several countries. Worldwide, more than 3,000 people experienced the disease, and close to 600 people died from it between 2010 and 2015, according to the World Health Organization.
The African countries most affected are the Democratic Republic of Congo (DR Congo) and Madagascar, followed by Mozambique, Uganda, and Tanzania.
The vaccine under development is based on the viral vector approach used in the successful AstraZeneca Covid-19 vaccine. It contains a harmless common-cold virus from chimpanzees that has been genetically engineered to transport genes into body cells. They then deliver instructions that trigger an immune response in the body against the disease.
Borrowing an approach from Covid-19 vaccines
Plague is caused by the bacterium Yersinia pestis. The disease can take different clinical forms, including bubonic, septicemic, and pneumonic.
The bubonic plague (the most common) and the septicaemic plague are transmitted by infected fleas frequently carried by rats. The pneumonic form, the most infectious, can spread from person to person through airborne droplets from coughing and breathing.
While the bubonic form has a case-fatality of 30-60% if not treated, the septicemic and pneumonic forms has a case-fatality ratio of 30-100% if left untreated. From the 14th century on, the disease spread through Europe, north Africa, and Eurasia, eventually killing millions of people.
The phase-one trial is funded by Innovate UK, which is part of the UK Research and Innovation, a branch of the government. It will involve at least 40 participants from age 18 to 55, with the aim to determine how effective it is in protecting against the disease, and assess any side effects.
The DRC and Madagascar are most affected
The biggest outbreak of plague in recent times happened in Madagascar in 2017.
Normally the island nation sees between 200 to 700 cases annually. The recent outbreak recorded 2,119 confirmed, probable and suspected cases of plague, including 171 deaths in four months, according to WHO. The outbreak was contained after the organization responded with $1.5 million in emergency assistance, and 1.2 million doses of antibiotics. These were used for treating those infected with the disease, and the more than 7,000 people who had contact with them.
This year between January and March, 37 suspected cases have been reported in Madagascar with at least 21 confirmed to be the bubonic form of the plague. During this period, approximately 9 deaths were recorded.
The DR Congo has recorded an average of around 100 cases of plague annually since 2013, with a surge in incidences, across a greater geography, since 2019. Last year as the country battled the Covid-19 pandemic, the total number of cases was over 450.
This week UNICEF raised concerns that the disease is making a comeback through a combination of poverty and continuing insecurity, particularly in the eastern province of Ituri, which accounts for almost all the cases and deaths in the country. Between 2020 and 2021, there were 578 cases and 44 plague-related deaths in the province, according to UNICEF.
As of June this year, there have been a total of 117 suspected cases and 13 deaths reported in the DR Congo with 10 deaths suspected to be due to pneumonic plague, according to WHO. This form of the disease is particularly concerning as it is the only version that can be transmitted from person to person.
“‘The coronavirus pandemic has shown the importance of vaccines to defend populations from the threat caused by bacteria and viruses,” Andrew Pollard, director of the Oxford Vaccine Group, said in a statement. “Plague threatened the world in several horrific waves over past millennia, and, even today, outbreaks continue to disrupt communities. A new vaccine to prevent plague is important for them and for our health security.”
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