The scientists who developed one of the first widely available vaccines against covid-19 are now setting their sights on a long-time microscopic foe: the plague. This week, researchers at the University of Oxford in the UK announced the start of a Phase I clinical trial testing out a potential vaccine for the plague. The experimental candidate is based on the same technology used to create their covid-19 vaccine, which has so far been administered to people in 180 countries.
Plague is a bacterial disease caused by Yersinia pestis. It’s typically spread through contact with infected animals or the fleas they carry, though it can also spread between people if the infection reaches the lungs and turns into pneumonic plague. Plague has been a nuisance of humanity for millennia, and sometimes a catastrophe, capable of causing widespread outbreaks of illness and death (the Black Death was a plague outbreak in the Middle Ages that devastated Europe). Nowadays, thanks to improved sanitation and antibiotic treatment, plague has become rare in most of the world. But it still periodically sickens and kills people, even in the U.S. Just last week, a 10-year-old boy in Colorado reportedly died from complications due to plague.
The ongoing threat of plague, particularly to rural regions in Africa and Asia where it remains endemic, was enough for the Oxford Vaccine Group to move forward with developing a potential inoculation against it.
“The coronavirus pandemic has shown the importance of vaccines to defend populations from the threat caused by bacteria and viruses. 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,” Andrew Pollard, director of the Oxford Vaccine Group, said in a statement.
Like the covid-19 vaccine jointly developed by Oxford and the pharmaceutical company AstraZeneca, the experimental plague vaccine is an adenovirus-based vector vaccine. These vaccines work by using a neutered adenovirus to deliver part of the genetic code of the target virus or bacteria to cells inside the body. This introduction causes cells to display proteins specific to the target germ, mimicking an infection and hopefully prompting an immune response that should train the body to recognise and respond to the real thing, should it ever come around. The adenovirus used in the vaccine (in this case, a common cold virus found in chimps) can’t replicate, preventing any real infection from taking place.
Phase I trials are the very first step of clinical research in humans and are mainly used to determine the safety of a potential drug or vaccine. This trial is set to enroll 40 healthy volunteers between the ages of 18 and 55, who will receive a dose injected into the upper arm; some are also expected to get a booster dose, either two or six months later. The volunteers will then be tracked for 12 months.
In their documentation of the study protocol, the researchers discuss the possibility of a rare blood-clotting condition that has been reported in connection to the Oxford/AstraZeneca vaccine. At this point, health officials are continuing to monitor the potential risk, though it appears to be very rare. One unanswered question is whether this risk is coming from the vaccine platform, as some researchers have speculated, or from the immune response to the coronavirus, which may mean no such risk would exist with other, similar vaccines. The volunteers will be asked to stay aware of potential symptoms that could be signs of the condition, including a sudden severe headache that doesn’t go away with treatment, unusual bleeding, and blurred vision.
Should the plague vaccine pan out, the researchers hope it can help difficult-to-reach populations in areas still being hit hard by the disease.
“Although antibiotics can be used to treat plague, many areas experiencing outbreaks are very remote locations. In such areas, an effective vaccine could offer a successful prevention strategy to combat the disease,” said Christine Rollier, associate professor of vaccinology at the Oxford Vaccine Group, in a statement.
This isn’t the only attempt to build on the success of covid-19 vaccines. Moderna is now using its mRNA platform to develop vaccines for the flu, as are other companies. And just yesterday, BioNTech, the German company that co-developed a vaccine with Pfizer, announced it was developing a mRNA vaccine for malaria.