Promising results from an experimental hookworm vaccine trial offer hope for the more than 400 million who contract the parasitic infection every year. 

The phase 2 study, published last month in The Lancet Infectious Diseases, was a double-blind clinical trial. Participants who received the Na-GST 1/Al–CpG vaccine candidate had significantly milder infections than those in the placebo group, as well as volunteers who received one of two other vaccine candidates. 

The vaccine specifically targets Necator americanus, which is the most common type of hookworm. By interfering with a certain protein in the worm, researchers say they can prevent N americanus from feeding on the blood of its host’s small intestine, causing the parasite to die. 

Exciting progress, but more research needed

It’s always a pleasant surprise when a vaccine or medical trial works as well as hoped for, said senior author David Diemert, MD, director of George Washington University’s Vaccine Research Unit.

“I have to say I was not expecting it to be that good,” he said.

Diemert’s results are promising and a good candidate for further testing, said Kaylee Herzog, PhD, a parasite biologist and curator of the parasite collection at the Museum of Southwest Biology at the University of New Mexico who was not involved in the study.

I have to say I was not expecting it to be that good.

“The road to a safe and effective hookworm vaccine is still a long and winding one,” Herzog told CIDRAP news. “But results like those reported here move us another step further along that road.”

Diemert said researchers on his team are searching for funding so they can conduct another phase 2 trial, which they’ll do in the field and in collaboration with communities where hookworm is endemic. The parasite is a pressing public health issue in tropical countries in which the sanitation infrastructure is poor and medical care can be harder to access. 

Vaccine would be a boon for global health

While some people have no symptoms, a hookworm infection can cause a host of health issues, including abdominal pain, rash, coughing or wheezing, fatigue, nutrient deficiencies, and anemia. Chronic reinfections in kids can slow their physical growth and mental development. 

Though the treatment for hookworms is fairly simple, treating someone once doesn’t protect them from future infections. And there’s evidence to suggest these medications are not always effective at clearing infections, especially after repeated use, said Diemert,  “It would be much better just to prevent it in the first place from ever happening.” 

Repeatedly administering anti-parasitic drugs is also an expensive and laborious process, added Herzog. 

There likely will not be a single vaccine that will be effective against all hookworms.

While it makes sense that Diemert and his colleagues designed a vaccine to specifically target N americanus, Herzog noted that other hookworm species also cause illness in humans. 

“There likely will not be a single vaccine that will be effective against all hookworms,” she said.

Still, if this experimental vaccine comes to fruition, she said it would be a boon for global health.