Two deaths from a Cyclospora outbreak, linked to tainted lettuce, have been confirmed in Michigan this summer, even as American research institutions announce a new vaccine candidate primarily targeting diarrheal diseases prevalent abroad. Thousands of cases of explosive diarrhea from the outbreak have spread across the United States. This domestic health crisis unfolds while global health priorities, often set by supranational bodies, dictate significant scientific investment.
A new vaccine candidate, WRSs2, named after the Walter Reed Army Institute of Research, has shown remarkable efficacy. It was tested jointly at Cincinnati Children's Hospital Medical Center and the Emory Vaccine Center's Hope Clinic in Atlanta. Results, published in The Lancet Infectious Diseases this year, indicated it was 89% effective at preventing shigellosis, a leading cause of diarrheal deaths globally.
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NPR reported that over 1 million people die from diarrheal illness, such as dysentery, every year. Nearly half of these deaths are children under age 5. Chad, for instance, faces the highest rate of childhood deaths, with roughly 1 in 140 children under 5 dying annually. Dr. Jahangir Hossain of the Gambia Medical Research Council Unit at the London School of Hygiene & Tropical Medicine has battled shigellosis for decades, first in Bangladesh and now in West Africa. He recalled that at the International Centre for Diarrhoeal Disease Research in Dhaka, sometimes 800 diarrheal patients would arrive in a single day.
No Shigella vaccine has ever been licensed, despite more than 100 years of research. Prior candidates achieved lower efficacy rates; one managed 74% in young adults but offered no protection in younger children, while an Israeli vaccine reached only 28% overall. WRSs1, an earlier candidate, showed 40% efficacy and more side effects. Dr. Hossain noted that the World Health Organization (WHO) typically seeks 60% efficacy for a vaccine to be considered acceptable. WRSs2's 89% efficacy significantly surpasses this global standard.
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The WRSs2 trial recruited 108 adults. Half received the vaccine, a weakened version of the shigella bacteria suspended in a liquid, in a dose slightly less than a shot-glass worth, taken twice a month apart. The other half received doses of salt water. Dr. Robert Frenck, a professor of pediatrics at Cincinnati Children's and director of its Center for Vaccine Research, co-led the trial. He stated the weakened bacteria is strong enough to trigger an immune reaction but shouldn't cause severe illness.
Dr. Kawsar Talaat, an infectious disease physician and vaccine scientist at the Johns Hopkins Bloomberg School of Public Health, highlighted the trial's deliberate exposure method. She reported that 81% of the placebo group became sick, experiencing diarrhea and fever before receiving antibiotics. Dr. Talaat called the vaccine's nearly 90% prevention rate "remarkable" and "the best efficacy we've ever seen." Volunteers were compensated approximately $250 a day for roughly a week, taking a quiz to ensure they understood the risks involved. Their commitment, Dr. Frenck said, facilitated a swift and efficient trial.
Domestic Costs and Misaligned Priorities
Diarrheal illness stands as the second leading cause of death for children worldwide, with Shigella being one of the more common bacterial causes. It spreads through contaminated food and water, flourishing where sanitation is poor. Children who contract Shigella often fall off their growth curves, never fully recovering. Dr. Hossain explained that prolonged diarrhea, increased hospitalization, malnutrition, and cognitive impairment often follow a Shigella infection. The peak risk occurs between 12 and 23 months of age.
Families in affected regions often travel one to three hours to reach a clinic, and diagnostic labs common in American hospitals are largely absent. Treatment relies on antibiotics, but resistance has reached over 80% for some antibiotics in certain regions. Dr. Hossain cited increasing antibiotic resistance as a critical factor making a vaccine especially important, listing ciprofloxacin, azithromycin, and ceftriaxone as antibiotics sometimes rendered ineffective. Dr. Talaat added that as these organisms become harder to treat, the need for a vaccine grows, drawing parallels to typhoid strains now almost impossible to treat with antibiotics. Vaccines, she suggested, could reduce antibiotic use and thus resistant strains.
The vaccine was not without side effects; over half of recipients reported a headache, and about 45% experienced some diarrhea after their dose, though no one required hospitalization. The authors deemed the safety profile acceptable, noting further work is needed to balance safety and efficacy. WRSs2 protects against a single species, Shigella sonnei. Dr. Frenck envisions a "holy grail" vaccine that would control ETEC, Campylobacter, and Shigella, allowing prevention with one or two administrations. All agreed that testing in children is the next crucial step, particularly in areas where poor sanitation contributes to high rates of diarrheal disease among young children.