BOSTON – Vaccination of U.S. children against rotavirus appears to be helping to curb rotavirus infections in adults, according to an analysis of data from more than 3,500 adults seen at one Chicago hospital during 2006-2010.
An analysis of stool bacterial cultures collected from 2,545 patients, aged 18 or older, at Northwestern Memorial Hospital during 2008-2010 showed a 49% drop in the prevalence of rotavirus compared with the prevalence in 988 specimens tested during 2006-2007, Dr. Evan J. Anderson reported in a poster at the meeting.
The finding "strongly suggests an indirect effect of pediatric rotavirus vaccination on rotavirus in adults," he said in the poster.
The timing of the effect correlates with rotavirus vaccine uptake among U.S. children. RotaTeq, the first of the two vaccines now on the U.S. market, received Food and Drug Administration licensing in 2006, but widespread U.S. rotavirus vaccination of children did not reach a high level until 2008, when a second formulation, Rotarix, also received FDA approval, said Dr. Anderson, an infectious diseases physician at Northwestern University and at Children’s Memorial Hospital in Chicago. Currently, more than 70% of U.S. children in the 2- to 6-month-old target age group for the vaccine actually receive it, he said in an interview.
To gauge the impact of widespread rotavirus vaccination on adult disease, Dr. Anderson and his associates reviewed laboratory records at Northwestern Memorial Hospital for bacterial stool cultures from adult specimens during 2006-2010. The data showed a 4.4% rotavirus prevalence rate in specimens taken during 2006-2007, and a 2.2% rate in specimens cultured during 2007-2010, a statistically significant difference.
"It’s a fantastic impact that changes the cost-effectiveness equation of giving rotavirus vaccine to kids, because you’re also protecting their parents and grandparents," Dr. Anderson said. He speculated that adults received protection against infection via a herd effect, with fewer children shedding and spreading rotavirus. The effect is important because "rotavirus is underappreciated as an adult pathogen." The diarrhea and vomiting it causes can have significant effects on adults, especially those with comorbidities, he said.
The evidence reported by Dr. Anderson and his associates corroborates another report of declining rotavirus prevalence among U.S. adults nationally. Researchers at the Centers for Disease Control and Prevention analyzed U.S. hospitalizations for diarrhea during 2000-2008 using data collected in the Nationwide Inpatient Sample. These investigators identified cases with a diagnosis of rotavirus infection by ICD-9-CM codes. The analysis showed that among people aged 15-24 years old, the incidence of rotavirus-associated diarrheal hospitalizations in 2008 was 65% less than in 2000-2006, a statistically significant difference (J. Infec. Dis. 2011;204:980-6). The incidence among adults, aged 25-64, ran 26% lower in 2008 compared with 2000-2006, and 21% lower among those aged 65 and older, but these differences did not reach statistical significance.
In an editorial accompanying the study, Dr. Roger I. Glass, director of the Fogarty International Center of the National Institutes of Health, called the CDC findings "remarkable observations on the indirect effects of the vaccine that could not have been anticipated before the vaccine was introduced" (J. Infec. Dis. 2011;204:975-7).
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