Serial norovirus infections in childhood suggest multiple genotype vaccine needed

An effective norovirus vaccine would likely decrease morbidity but may need to target several genotypes, according to recent study results published in Clinical Infectious Diseases.

Mayuko Saito, MD, MPH, PhD, of the department of virology at Tohoku University Graduate School, Japan, and colleagues followed 220 children until age 1 year and 189 children until aged years to estimate norovirus infection and diarrhea incidence in a Peruvian community.

Mayuko Saito

Overall, 80% of patients had at least one infection and 38% had at least two by age 1 year. Forty-six percent of the first infections were asymptomatic during the first year of life, 33% were symptomatic and 21% were undefined.

Genotype II (GII) infections occurred three times more frequently than genotype I (GI). Overall, 18 genotypes were identified and 41% were GII.4 (G4). Thirty-four repeat infections were GI and 231 were GII. Six percent of repeat infections were by the same genotype.

The median length of excretion duration for GII was 34.5 days compared with 8.5 days for GI.

“Clearly, development of an effective norovirus vaccine represents the next issue of importance to control diarrheal deaths and hospitalization,” the researchers wrote. “A vaccine based on the Norwalk virus-like particle demonstrated protection against homotypic experimental challenge; other approaches are under development. However, our study demonstrates that children can mount an effective immune response to norovirus, but this response is restricted by viral genotype.”

In an accompanying editorial, Benjamin Lopman, PhD, of the CDC’s National Center for Immunization and Respiratory Diseases, and Gagandeep Kang, PhD, of Christian Medical College in India, wrote that one of the most crucial findings of the study is that past GII infections protect against subsequent infections and disease.

“Notably, substantial decreases in disease incidence did not come until after two previous GII infections, suggesting that multiple doses of vaccine may be required to generate a protective immunity, at least among naive children,” they wrote.

For more information:

Saito M. Clin Infect Dis. 2013;doi:10.1093/cid/cit763.

Lopman B. Clin Infect Dis. 2013;doi:10.1093/cid/cit785.

Disclosure: The study was funded in part by Sixth Framework Programme of European Union, Population Health Metrics Research Consortium Project, and the CDC. The researchers report no relevant financial disclosures.