By Rachel Pittluck
Public health practitioners have a new weapon in the arsenal against diarrheal disease. A study published last week in the New England Journal of Medicine found that three doses of a new oral rotavirus vaccine could prevent two-thirds of the deaths and hospitalizations caused by the infection.
Though it doesn’t have the same name recognition as cholera or E. coli, rotavirus is a leading cause of diarrheal disease and a major killer worldwide. Researchers estimate that the virus is responsible for 37% of deaths from diarrhea among children under 5. More than 85% of those deaths occur in Africa and Asia. The virus is spread through the fecal-oral route, but improvements in water, sanitation, and hygiene are not sufficient to prevent transmission. Vaccination is therefore essential to controlling the virus’s spread.
The NEJM paper presents the first results of a large randomized controlled trial conducted by Doctors Without Borders to assess the safety and efficacy of a heat-stable, live, oral bovine rotavirus pentavalent vaccine (BRV-PV) among infants in Niger. No safety concerns were identified, and the researchers found that the vaccine had an efficacy of 67% against severe rotavirus gastroenteritis and offered protection against more moderate illness as well. This is better than the two currently licensed vaccines performed in similar settings.
In middle- and high-income settings, rotavirus vaccines have shown an efficacy of 80-90%. But there appears to be an efficacy gradient based on socioeconomic status even within countries. It is not clear what accounts for the lower performance in impoverished settings. Experts have suggested that the difference may be related to poorer nutritional status, differences in the gut microbiome, enteropathy, or co-infections. Other hypotheses include an earlier age of first infection or maternal exposure to the virus, leader to higher rates of natural immunity, or co-administration of the oral polio vaccine, which may reduce rotavirus antibody levels.
The introduction of rotavirus vaccination in the United States drastically reduced rates of infection, but cost and supply chain constraints have slowed its uptake where it is most needed. As reported by the New York Times and NPR, cold-chain capacity represents a major barrier to increasing rates of rotavirus vaccination, particularly in sub-Saharan Africa and southern Asia. Both existing vaccines require constant refrigeration. That’s what makes this new vaccine so exciting. Thanks to a process of freeze-drying, BRV-PV can remain stable for two years at 37°C/98.6°F and six months at 40°C/104°F. This will make it easier to deliver the vaccine in settings where refrigeration is unavailable or electricity unreliable, including many low-income countries.
BRV-PV, which is developed and manufactured by the Serum Institute of India, will need to be approved by the World Health Organization before it can be distributed widely through Gavi, the Vaccine Alliance, and United Nations programs. But once this process is complete, the vaccine is expected to be cheaper than existing options.