Approximately 60,000 people die of rabies every year, according to the World Organization for Animal Health (OIE). However, with more than 95% of human cases caused by dog bite, only 70% of the canine population in high-risk zones would need to be vaccinated to reduce that number to virtually zero, OIE said. Indeed, systematic vaccination of dogs is today considered the most effective method of breaking the disease cycle and leading to the elimination of rabies.
For this reason, and with the financial aid of international donors, OIE created a rabies vaccine bank in 2012. This mechanism guarantees the availability of high-quality vaccines that comply with OIE’s international standards.
Now, a Washington State University-led research team has determined that rabies vaccines stored at warmer temperatures still protect against the disease in dogs.
The work, published in the journal Vaccine, could lead to improved vaccination coverage in hard-to-reach rural areas in Africa and Asia where electricity for cooling is limited.
“Thermo-tolerant vaccines were a really important feature of the campaign to eliminate smallpox. We hope it will have the same effect for eradicating rabies,” said Felix Lankester, lead author and clinical assistant professor in the Washington State University Paul G. Allen School for Global Animal Health.
Recommendations by the World Health Organization are for vaccines to be transported and stored in a “cold chain” at 2-8°C (35.6-46.4°F). Lankester and his colleagues found that Nobivac, a commonly used rabies vaccine, produces the same level of protective antibodies in dogs after being stored for six months at 25°C (77°F) and for three months at 30°C (86°F).
“The ability to distribute vaccines widely outside the cold chain will allow for more consistent coverage across communities,” Lankester said. “It could be a quantum shift in how vaccines are delivered.”
Eradicating one of the deadliest diseases
“Human rabies from dog bites has the highest fatality rate of any human infectious disease,” said Guy Palmer, Washington State senior director of global health. However, “rabies is easily preventable with regular dog vaccinations.”
Vaccinating 70% of the dog population will protect people and wildlife — such as endangered African wild dogs — from the disease.
Washington State, in collaboration with the Serengeti Health Initiative, has been working to control rabies in areas of northern Tanzania through annual mass dog rabies vaccination campaigns, but rabies continues to be prevalent, in part because of the challenges of transporting vaccines to remote areas where vulnerable people live in resource-poor communities.
Mass vaccination teams generally only visit communities once a year, if they can get there at all. When new dogs are born or move into the community, the level of protection against rabies drops. In community-led programs, thermo-tolerant vaccines could be stored in the community so local coordinators could vaccinate the entire dog population.
“Through community-led programs, coverage could be kept relativity consistently high, which would reduce the likelihood of rabies returning to a community,” Lankester said. “These findings also give confidence to those working to control rabies that if vaccines are kept outside of the cold chain for a small time, they don’t have to be thrown away.”
In the next phase of the research, Lankester and his colleagues will test the effectiveness of using low-tech cooling options for storing rabies vaccines in rural communities.