Rotavirus decreased in adults after widespread vaccination among children

IDSA 49th Annual Meeting

BOSTON — Rotavirus prevalence decreased by nearly 50% in a cohort of adults after vaccination for the infection was introduced, according to findings presented here at the IDSA 49th Annual Meeting.

The trial was conducted in the wake of a decline in pediatric rotavirus (RV) incidence that suggested indirect vaccine protection, even in children who had not been vaccinated. The researchers aimed to determine whether a similar protective effect may occur in adults.

The trial was conducted between 2006 and 2010. Evan J. Anderson, MD, assistant professor of Pediatrics and of Medicine at Northwestern University’s Feinberg School of Medicine, and colleagues, collected stools between February and May of those years, and submitted them for bacterial stool culture. The samples were frozen and later tested with Rotaclone (Meridian Bioscience).

Prevalence rates for 2006-2007 were compared with those from 2008-2010.

The Rotaclone test detected RV in 4.4% of cultures from 2006-2007 and 2.2% of cultures from 2008-2010, indicating a decline of 48.5% (P=.0014). A trend toward the lowest rates occurred in the latter years, a pattern which also was observed in RV in children. However, bacterial pathogens in stool cultures remained stable between the two study periods (3.3% vs 3.7%; P=.69).

Both G- and P-types of RV were identified in 70% of test-positive samples. Over the 5 years, G2P[4] accounted for 24%, G1P[8] 22%, G3P[8] 11%, and G12P[6] 9%. Marked year-to-year variation in the predominant circulating genotype was observed.

Thirty-percent of RV-positive individuals were immunocompromised, which included HIV, stem cell transplantation, solid organ transplantation, active cancer or high-dose steroids. These individuals remained stable over time.

Real-time polymerase chain reaction followed by gel electrophoresis with selective confirmation by sequencing was used to genotype the isolates. Results from 2006 were only from hospitalized adults <72 hours from admission. Results for the remaining years included outpatients and inpatients. Individuals younger than 18 years who had a duplicate bacterial stool culture were excluded.

No differences were observed with regard to baseline demographic data or outcomes in RV-positive individuals in the two time periods.

“A 48.5% decline in the prevalence of RV was observed in adults that coincide with similar declines observed in pediatric RV disease that occurred following widespread pediatric vaccination,” the researchers wrote. “This strongly suggests an indirect effect of pediatric RV vaccination upon adult rotavirus. We observed substantial year-to-year variation in the most prevalent circulating RV genotype in adults.” — by Rob Volansky

Disclosure: Dr. Anderson reported being a grant investigator and scientific advisor for and receiving a research grant and a consulting fee from Merck; being on the speaker’s bureau and receiving speaker honoraria from Merck; being an independent contractor and receiving honoraria for writing CME from Medscape; being a grant investigator for and grant recipient from Meridian Bioscience; and being a scientific advisor for and receiving a consulting fee from GlaxoSmithKline.

For more information:

Anderson E. #3790-LB-26. Presented at: IDSA 49th Annual Meeting; Oct. 20-23, 2011; Boston.

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