A study involving 84 volunteers showed that an experimental norovirus vaccine provided considerable protection against infection and symptoms of gastroenteritis, researchers from Baylor College of Medicine reported in NEJM (New England Journal of Medicine). The authors added that theirs is the first study to show protection from norovirus illness due to a vaccine. To date, the only treatment for norovirus illness is to take plenty of fluids to prevent dehydration, and drugs to treat the symptoms of diarrhea and vomiting.

First author, Dr. Robert Atmar, said:

“This study shows it is feasible to make a vaccine that will protect against norovirus infection and the illness it causes.

Given the number of norovirus infections that occur annually and the healthcare costs associated with these infections, it is worthwhile to continue the investigation of vaccine candidates to prevent this illness caused by these viruses.”

The study initially involved 90 healthy individuals aged from 18 to 50 years at four sites across the USA. They were divided into two groups:

  • The vaccine group – they were administered the vaccine as a powder in the nose (intranasally) in two doses
  • The placebo group – they were also administered a powder in the nose in two doses, but the powder had no active ingredient

After about three weeks, following the second vaccine, 84 of the participants were exposed to norovirus. You have to wait three weeks so that the immune system can respond.

The researchers reported that:

  • In the vaccine group – 61% became infected and only 37% developed symptoms of gastroenteritis. The ones who became ill in this group had milder symptoms compared to those in the placebo group.
  • In the placebo group – 82% became infected and 69% developed symptoms of gastroenteritis

It is possible to become infected and to have no symptoms of gastroenteritis – this simply means the virus is detected in the patient, but he/she did not get ill. The vaccine’s main goal is to prevent symptoms of stomach upset.

Dr. Atmar said:

“The vaccine induced a significant immune response in 70 percent of people who received it and offered protection against both illness and infection. However, it offered greater protection against illness than infection. In other words, compared to placebo recipients more persons who received the vaccine did not develop gastroenteritis, even if they were infected by the virus.”

Norovirus 4
Norovirus particles in feces seen through an electron-microscope

Noroviruses are part of the Caliciviridae family of viruses. They are the most common cause of gastroenteritis (stomach upset) in the developed world. According to WHO (World Health Organization), approximately 90% of all epidemic non-bacterial gastroenteritis occurrences worldwide are caused by noroviruses.

Norovirus infection is sometimes referred to as winter vomiting disease, because it more commonly appears during the winter months. However, infections may occur during any month of the year.

After a patient recovers from a norovirus infection, he/she has about 14 weeks’ worth of immunity, which is usually incomplete. People with blood type O are more susceptible to infection, while those with types AB and B are the least susceptible.

Norovirus infection outbreaks are more likely to occur in closed or semi-closed environments, such as cruise ships, schools, dormitories, prisons, overnight camps, and long-term care facilities – places where human-to-human contact is common. It is commonly called the cruise ship virus.

Infection can occur through human contact, consuming contaminated foods or water, and touching surfaces which are tainted with the virus. Food handled by an infected person is also a potential source of infection.

According to CDC (Centers for Disease Control and Prevention) estimates, about 21 million individuals in the USA are infected by noroviruses every year.

The researchers are now trying to determine whether administering the vaccine as an injection might provide even better results. They are also testing the vaccine on other virus strains.

The vaccine is being developed by LigoCyte. Its CEO, Donald P. Beeman said:

“We look forward to continued development of our VLP (virus-like particle)-based norovirus vaccine candidates including additional clinical studies of our bivalent intramuscular vaccine.”

Fellow researcher, Dr. Mary Estes, said:

“The collaborative team environment at Baylor has been instrumental in moving our basic science discovery toward the clinic and these studies show for the first time that a non-replicating vaccine given intranasally can induce protection against a gastrointestinal pathogen. We had been told this couldn’t be done.”

Written by Christian Nordqvist