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Experimental Vaccine Reduces Norovirus Symptoms

GI infection can cause severe vomiting and diarrhea (October 5)

Mixed results have been reported from a phase I/II study of an intramuscular bivalent (GI/GII) norovirus vaccine candidate (Takeda Pharmaceuticals) in 98 healthy adult volunteers aged 18 to 50 years who were challenged with the most commonly occurring norovirus (genotype GII.4) that causes gastroenteritis.

The study demonstrated that two doses of the experimental bivalent norovirus were well tolerated, and that the candidate vaccine had a clinically relevant effect on the incidence of norovirus illness after challenge, as well as on the severity in breakthrough cases. In addition to the vaccine’s effect on clinical illness, a positive trend toward a reduction in viral shedding in stool was observed.

The new data were presented Oct. 5 at the IDWeek 2013 conference in San Francisco, California.

Key results from the study include the following:

  • The trial’s primary composite endpoint — a reduction in the incidence of acute gastroenteritis of any severity and laboratory ascertainment for norovirus — was not met.
  • There were no cases of severe vomiting and/or diarrhea in the vaccine group versus four in the placebo group following challenge with live norovirus (0.0% vs. 8.3%, respectively; P = 0.054).
  • Although there was a numerical reduction (68%) in moderate or severe vomiting or diarrhea with the vaccine, this did not reach statistical significance (6.0% vs. 18.8%; P = 0.068).
  • A secondary endpoint was met, with a 52% reduction in vomiting and/or diarrhea of any severity (20% of people who received the vaccine versus 41.7% of those who received placebo; P = 0.028).
  • In those who experienced illness symptoms, the severity of illness was significantly reduced in vaccinees versus placebo recipients (mean severity scores of 3.1 vs. 5.0, respectively; P = 0.023).
  • Side effects were mostly mild and of limited duration, with pain at the injection site being the most common local reaction. The most common systemic reaction was headache.

Source: Takeda; October 4, 2013.

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