Daniel M. Keller, PhD

October 23, 2011

October 23, 2011 (Boston, Massachusetts) — Calculated risk-to-benefit ratios argue strongly in favor of continued immunization with the currently available vaccines against rotavirus infection to prevent rotavirus gastroenteritis in young children. Rishi Desai, MD, MPH, a pediatric infectious disease physician and epidemic intelligence service officer in the division of viral diseases at the Centers for Disease Control and Prevention in Atlanta, Georgia, reported this finding during a poster session here at the Infectious Diseases Society of America 49th Annual Meeting.

A previous oral rotavirus vaccine (RotaShield, Wyeth-Ayerst) was withdrawn from the market in 1999 after being associated with approximately 10 excess intussusception cases per 100,000 vaccinated infants. The current oral vaccines (Rotarix, GlaxoSmithKline; RotaTeq, Merck) were introduced in 2006; in Latin America, they have been associated with about 1 to 2 excess intussusception cases per 100,000 vaccinees in the first week after the first dose of vaccine. Excess cases are the number of cases above the baseline incidence of intussusceptions in the cohort.

Using these data, Dr. Desai and colleagues calculated the benefits and potential risks for rotavirus vaccine. They used data from Latin America because the vaccine was introduced there the earliest. The study primarily relates to Rotarix, which is the vaccine used predominantly in the area.

Vaccine coverage data were obtained from World Health Organization country-specific estimates. Baseline rates for intussusception hospitalizations were from pooled global estimates, and the researchers estimated the number of rotavirus deaths and hospitalizations prevented using published data on prevaccine rotavirus burden and vaccine effectiveness estimates.

Vaccine Benefit Far Outweighs Vaccine-Associated Morbidity

"We found that essentially for every 1 child who dies of vaccine-associated intussusception, we would save about 400 children from death from rotavirus, and for every 1 child who is hospitalized for intussusception because of the vaccine, we would prevent about 841 children from being hospitalized for rotavirus," Dr. Desai told Medscape Medical News.

By the investigators' calculations, rotavirus vaccine would avert 144,746 hospitalizations for rotavirus gastroenteritis and 4124 rotavirus deaths if a hypothetical cohort of 9.5 million infants in 14 Latin American countries was vaccinated. At the same time, it could potentially cause 172 excess intussusception hospitalizations (1.8/100,000 vaccinated infants) and 10 excess deaths (0.11/100,000 vaccinated infants). These figures result in risk-to-benefit ratios of 1:841 for hospitalization and 1:395 for death in favor of vaccination.

Dr. Desai concluded that the benefits far outweigh the potential risks. Although the risk occurs within a week of vaccination, the benefit lasts up to 5 years. He said the take-home message is that "there seems to be an intussusception risk in Latin America and that the benefits outweigh that risk tremendously. In terms of making a decision about vaccination, I would recommend continuing vaccination because of the tremendous benefit that you get relative to the risk."

There are no major standards of acceptable risk-to-benefit ratios for these or other vaccines. "As a physician and a clinician, what I would do is explain these risks and benefits to parents and try to make sure that they make the best decision for their child," he said. "What we wanted to do is make sure this number is available so that people can make a direct comparison and get a better sense of what they're really getting in terms of giving [the vaccine]."

Samuel Katz, MD, professor and chair emeritus of the Department of Pediatrics at Duke University Medical School in Durham, North Carolina, told Medscape Medical News that this is "a well-conducted amalgam of studies in 14 countries looking at the incidence of rotavirus disease and looking at prevention with vaccine.

"What it raises is an ethical question rather than a scientific question. I don't know enough about the 14 countries in which this was done to ask: 'If we know that this vaccine may on rare, rare occasions cause intussusception, would this enhance the surveillance of youngsters who got the vaccine, and would anything that suggested they were having an intestinal disorder call them more quickly to medical attention?' Intussusception should not be a fatal disease; it's a condition that's readily rectified."

The study received no commercial support. Dr. Desai and Dr. Katz have disclosed no relevant financial relationships.

Infectious Diseases Society of America (IDSA) 49th Annual Meeting: Abstract 331. Presented October 21, 2011.


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