Rotavirus Vaccine May Also Prevent Related Infant Seizures

Larry Hand

November 21, 2013

A full course of rotavirus vaccine administered to infants may reduce the risk for rotavirus-related seizures by as much as 21% during the year after vaccination, according to an article published online November 21 in Clinical Infectious Diseases.

The finding suggests an additional, surprising benefit of the vaccine intended to protect infants against intestinal infections caused by rotavirus, the researchers write. They project that the reduction could translate to more than $7 million in healthcare cost savings annually by preventing 1000 hospitalizations and 5000 emergency department visits.

Daniel C. Payne, PhD, MSPH, from the Division of Viral Diseases, Epidemiology Branch, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, and colleagues conducted a retrospective analysis of children born after February 28, 2006, the date of US licensing of rotavirus vaccine, through November 2009.

They analyzed records from the Vaccine Safety Datalink (VSD) database, a collaborative project of the CDC and managed care organizations (MCOs) that captures epidemiological, clinical, and vaccination information on about 3% of the US population. The study population for their analysis consisted of 250,601 children, 186,502 of whom had been fully vaccinated against rotavirus and 64,099 of whom had not been vaccinated against rotavirus, with most ranging in age between 8 and 18 months.

The researchers identified 2244 first-time seizures (1575 for fully vaccinated children and 669 for unvaccinated children). The rate of first-time seizures was 1145 per 100,000 person-years among fully vaccinated children and 1212 per 100,000 person-years among unvaccinated children. The overall seizure rates (first-time and repeat seizures) were 1383 per 100,000 person-years among vaccinated children and 1502 per 100,000 person-years among unvaccinated children.

Adjusting for sex and age at last vaccine dose, the researchers observed a statistically significant effect of about an 18% reduction in first-time seizures and 21% reduction in all seizures (risk ratio [RR], 0.816 [95% confidence interval (CI), 0.729 - 0.914] for first-time seizures; RR, 0.790 [95% CI, 0.714 - 0.875] for all seizures).

Mechanism and Surprise

The "most probable mechanism" for this risk reduction is the vaccine's protective effect on "systemic rotavirus infection, including extraintestinal complications involving the central nervous system," the researchers write. The vaccine may also prevent rotavirus-related nitric oxide elevation in cerebrospinal fluid that causes neurotoxicity or calcium channel fluctuations that lead to neurotransmitter dysregulation, they write.

"I think the biologic mechanism, although it's speculative, is believable and plausible, and I think it probably is true because I think this was a carefully done epidemiologic study, and I doubt they've made a mistake in their rate," Geoffrey A. Weinberg, MD, from the Department of Pediatrics at the University of Rochester School of Medicine and Dentistry in New York, told Medscape Medical News. "I think it's a pleasant surprise."

Dr. Weinberg, who wrote an accompanying editorial about the study, said the study findings present an added benefit of rotavirus vaccine but do not alter the reasons for having children immunized. "Is it a real reason to run out and get immunized? No. I think the real reason to run out and get immunized against rotavirus is to not have rotavirus diarrhea."

New Paradigm?

Another "unique feature" of this study is the use of VSD data to find beneficial effects when the VSD is normally used to investigate vaccine adverse events, Dr. Weinberg writes in his editorial. "The description of a 'beneficial effect,' rather than an 'adverse event,' might suggest a new paradigm for future VSD studies," he writes.

Limitations of the study include lack of generalization to children vaccinated with rotavirus vaccine RV1, because more than 99% of the study children had RV5 vaccinations. Another factor limiting generalization is the fact that all study children were enrolled in MCOs and were not necessarily representative of all US children.

The researchers conclude, however, that "we found that a full course of rotavirus vaccination was associated with statistically significant reductions in the risk of childhood seizures during the year following last rotavirus vaccination. This reduction in childhood seizures complements the well-documented vaccine-related benefit of preventing US diarrhea hospitalizations."

In his editorial, Dr. Weinberg concludes: "Work such as this not only is interesting scientifically, but provides yet another reason to strongly promote universal rotavirus immunization. In addition, the work provides as an opportunity to reflect on the fact that sometimes, unexpected effects of vaccination are beneficial and are a cause for celebration, rather than the more commonly publicized concern for unexpected adverse effects."

This research was funded by the CDC. One coauthor's institution has relevant financial relationships with US-licensed rotavirus vaccine companies and has received grant funds from the US government. Another 2 coauthors' institutions also have received grant funds from the US government. The other authors and the editorialist have disclosed no relevant financial relationships.

Clin Infect Dis. Published online November 21.

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