Pediatric Rotavirus Vaccination Reduces Prevalence in Adults

Daniel M. Keller, PhD

November 03, 2011

November 3, 2011 (Boston, Massachusetts) — The prevalence of rotavirus (RV) in adults dropped by half after widespread pediatric vaccination against the virus, Evan Anderson, MD, assistant professor of pediatrics and medicine at Northwestern University Feinberg School of Medicine, Chicago, Illinois, reported during a poster session here at Infectious Diseases Society of America 49th Annual Meeting.

RV occurs as a pathogen in the winter and spring in children and adults. Because it was not known whether the vaccination of children would indirectly protect unvaccinated adults, Dr. Anderson and colleagues tested stool samples from adults with diarrheal disease to look for the prevalence of RV.

In this retrospective study conducted at Northwestern Memorial Hospital in Chicago, stool samples were collected from February to May each year from 2006 to 2010. In the first year, samples were taken only from hospitalized adult patients (18 years or older) less than 72 hours from admission. In subsequent years, samples from inpatients and outpatients were included.

The widespread RV vaccination of children began in the United States in 2006, and a dramatic decline in RV disease was seen by 2008. Baseline data from 2006/07, before the impact of the vaccine was seen, showed a 4.4% prevalence in adults (43 of 988).

Dr. Anderson noted that 2008 was the beginning of the large impact of RV vaccination in children. "Carrying through to 2010, [there was] almost a 50% drop in the prevalence of rotavirus in adults who had samples sent for bacterial stool culture," he told Medscape Medical News. This "suggests that there's herd immunity or indirect protection of adults related to pediatric rotavirus vaccination."

Adult Prevalence Rate Drops After Pediatric Vaccination

From 2008 to 2010, RV was detected in 2.2% of adult stool samples (57 of 2545), a 48.5% decline from the previous period (P = .001). The prevalence declined in both hospitalized patients (6.1% to 3.5%; P = .04) and outpatients (3.2% to 1.7%; P = .03). In contrast, the prevalence of routine bacterial stool pathogens remained stable from 2006/07 (3.3%) to 2008 to 2010 (3.7%; P = .69).

The demographics of the adults with stools that were positive for RV were similar for the 2 time periods. Thirty percent of them were immunocompromised because of HIV infection, stem cell or solid organ transplantation, cancer, or high-dose steroid therapy.

Dr. Anderson said that marked variations in the predominant RV genotypes occurred from year to year. The vaccine "is not completely protective against all genotypes, but there is evidence that [vaccinating children] does decrease the total burden of rotavirus seen in adults," he said, presumably because the children are not transmitting it to parents, grandparents, or other contacts.

"Internists never think about rotavirus as a pathogen in adults,...[but] there was a huge drop in terms of prevalence...that correlates directly with...a widespread impact in kids," he said. "This really changes the equation when you think about the cost-effectiveness of vaccinating kids against rotavirus. There's huge herd immunity impact that's also affecting the adult burden of disease."

Larry Pickering, MD, from the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention, and professor of pediatrics at Emory University School of Medicine in Atlanta, Georgia, told Medscape Medical News that RV is not considered a major problem in adults and is usually not tested for as a cause of adult diarrhea, "so the real magnitude of disease is unknown."

"This poster is nice because it gives an idea of how much rotavirus disease was in the adult population they studied. It was very small, but it was clearly there," he added.

Dr. Pickering said that RV does not cause severe disease or hospitalization in adults, "but there are subsets of adults who may be immunocompromised, or the elderly, who, if they get diarrhea, they get dehydration, and that can be pretty significant in those populations.... One of the unexpected benefits of this vaccine is that it does prevent transmission of rotavirus from infants — because the disease is prevented in infants — to adult populations."

Dr. Anderson reports receiving research support for the first year of the study (2006) from Meridian Biosciences and Merck Sharp & Dohme; serving as a consultant for Merck and GlaxoSmithKline; being on the speakers' bureau for Merck; and receiving honoraria from Medscape for writing Continuing Medical Education materials. Dr. Pickering has disclosed no relevant financial relationships.

Infectious Diseases Society of America (IDSA) 49th Annual Meeting: Abstract LB-26. Presented October 22, 2011.

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