CDC Releases Toolkit to Help Clinicians Combat Norovirus Disease Outbreaks

No vaccine currently exists to prevent human norovirus infection, and there is no specific therapy available to treat it. However, a proof-of-concept study (abstract) recently reported in the New England Journal of Medicine (NEJM) builds on earlier research that showed a monovalent intranasal vaccine formulated using Norwalk virus (the prototype human norovirus) viruslike particles (VLPs) induced virus-specific serum antibodies in vaccine recipients.

The purpose of the NEJM study was to determine whether the vaccine could provide protection against illness after a homologous norovirus challenge.

The double-blind, multicenter study involved 98 patients, 77 of whom completed all phases of the study and were included in the final efficacy analysis. Patients initially were randomized to receive either two doses of an adjuvanted vaccine containing 100 micrograms of Norwalk virus VLPs or two doses of a placebo vaccine.

Study participants then underwent a Norwalk virus challenge consisting of oral administration of about 10 times the amount of virus required to infect 50 percent of individuals to whom it is administered.

The authors report that Norwalk virus-associated gastroenteritis occurred in 69 percent of placebo recipients compared with 37 percent of those who received the vaccine. Vaccination also reduced the relative frequency of Norwalk virus infection, with infection occurring in 82 percent of placebo recipients and 61 percent of vaccine recipients. Disease severity was reduced in those who received the vaccine compared with placebo recipients, and onset of illness was delayed. No vaccine-related severe adverse events occurred in either group during the study.

"This study shows that it may be possible to use a vaccination strategy to prevent norovirus disease," the authors concluded.