Cholera vaccine developed by University of Maryland wins FDA approval

University of Maryland made cholera vaccine may be in use for travelers by fall.

Federal regulators have approved a cholera vaccine developed by the University of Maryland that will provide U.S. travelers with the first defense against the virulent infection common in many poor countries.

The FDA approved Vaxchora this month, and its maker says it could be available as early as this fall. Research continues with the goal of expanding global protection against an infection that still sickens millions of people each year.

"Very healthy people can get very sick very quickly from cholera," said Dr. Kathleen M. Neuzil, director of the university's Center for Vaccine Development, where the vaccine was created. "This marks a significant public health milestone."

The vaccine was developed in the 1980s, but never made it to market in the United States. The Maryland center partnered with Redwood City, Calif.-based PaxVax recently to study the vaccine in humans and seek FDA approval.

Because there is little cholera in the United States, researchers infected volunteers with the bacteria in what is known as a challenge study — the first time the FDA has permitted such a plan for testing vaccines in humans. Vaxchora was found to be about 90 percent effective at 10 days and close to 80 percent effective at three months.

Those studies were completed more quickly than if researchers had to wait for study subjects to become infected in the environment, said Dr. Wilbur H. Chen, chief of the vaccine center's adult clinical studies section, who led the human studies. That helped to win FDA approval in about seven years, or half the time that might have been expected, he said.

Chen and Neuzil said Vaxchora will be useful primarily to travelers to countries in the Caribbean, Africa and Asia, whose only defense now against cholera is to avoid water and food that might be contaminated with bacteria.

But the real benefit is expected to come once researchers are able to vaccinate vulnerable people in dozens of poor countries where cholera is endemic because of poor sanitation and a lack of clean water.

Cholera is caused by Vibrio cholerae bacteria. It causes watery diarrhea that can lead quickly to extreme dehydration. More than 100,000 people around the world die from the disease each year.

The vaccine will need to be tested in other countries before it can be used. Chen said it might have to be reformulated to work on people who have been infected with cholera before and on small children who might not be able to tolerate swallowing a 3-ounce oral vaccine.

The long-term efficacy of the vaccine also will need to be evaluated.

Two other cholera vaccines have been approved by the World Health Organization, but they require two doses taken two weeks apart, and are not approved for use in the United States.

Public health researchers say it can be problematic to administer a second dose two weeks later, especially because cholera epidemics often occur after disasters. An epidemic in Haiti that started after the 2010 earthquake has sickened nearly 800,000 people and killed more than 9,200, according to world health reports.

A vaccine that requires only one dose would be helpful, said Justin Lessler, an associate professor of epidemiology in the Johns Hopkins Bloomberg School of Public Health. But any addition to the world's stockpiles of vaccine will help save lives.

"Any new vaccine and any new manufactures would be really good," Lessler said. "Last year there were somewhere like 2.5 million doses of oral vaccine stockpiled for 1.5 billion people at risk globally. The focus of cholera vaccines has been putting out fires, vaccinating people after an outbreak has begun, rather than stopping outbreaks from happening."

Lessler said cholera is easily treated with salt-and-sugar-infused water, and IV fluids for more advanced cases, but infections still kill people because of the quick onset and lack of resources in underdeveloped countries.

He said improving public water supplies and sewage treatment are important long-term measures to prevent cholera.

Federal officials stressed the importance of preventive measures such as drinking bottled water and washing hands frequently in addition to vaccination.

Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said, "Vaxchora represents a significant addition to the cholera-prevention measures currently recommended by the Centers for Disease Control and Prevention for travelers to cholera-affected regions."

Preventive measures can be "challenging to follow effectively," said Dr. Lisa Danzig, PaxVax's vice president of clinical development and medical affairs. "Until now, U.S. travelers have not had access to a vaccine to help protect against this potentially deadly pathogen."

meredith.cohn@baltsun.com

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