Intussusception and an oral rotavirus vaccine

A critical time for rotavirus vaccines: a review

Universal introduction of rotavirus vaccines into childhood immunization programs is expected to substantially reduce the mortality from rotavirus gastroenteritis in developing countries (currently estimated at 702,000 annual deaths among children less than 5 years of age). In addition, it is expected to virtually eliminate hospitalizations due to rotavirus gastroenteritis in developed countries. Two rotavirus vaccines, Rotarix (GlaxoSmithKline Biologicals, Belgium) and RotaTeq (Merck & Co., USA) have recently completed Phase III clinical trials, each involving more than 60,000 children. Both vaccines appear safe with respect to intussusception, and are highly efficacious in preventing severe gastroenteritis due to rotavirus strains carrying predominantly serotype G1. The monovalent human rotavirus vaccine Rotarix, possessing serotype P1A[8],G1, is being first introduced into developing countries, whereas the pentavalent bovine-human reassortant rotavirus vaccine RotaTeq, comprising G-types G1, G2, G3, G4 and P-type P1A[8], will be initially introduced into the USA and Europe. Current disease burden estimates and economic justification will be required wherever the vaccines are introduced. Confirmation of the safety of both vaccines will require extensive postlicensure evaluation in which it will be key to assure adherence to administration of the first dose of either vaccine before 3 months of age. Assessment of the ability of each vaccine to provide protection against an increasingly diverse population of rotavirus strains will crucially depend on continuous global strain surveillance. Finally, efforts to improve existing rotavirus vaccines and to develop alternative vaccines should continue, so as to ensure that the prerotavirus vaccine era is consigned to a historical context.

Rotavirus infection and intussusception in Tunisian children: implications for use of attenuated rotavirus vaccines

BACKGROUND

A licensed rotavirus vaccine was withdrawn from use because of an increased risk of intussusception. The association of rotavirus vaccination with intussusception raised concerns about a potential link between natural rotavirus disease and intussusception. The objectives of the present study were to determine whether an epidemiological association with natural rotavirus infection existed.

METHODS

From 1984 to 2003, all children younger than 5 years with intussusception were retrospectively identified by medical charts, and from 1995 to 2003, a prospective surveillance study of rotavirus infection in children younger than 5 years was independently conducted. Epidemiological characteristics of intussusception and rotavirus infection were then compared.

RESULTS

A total of 533 cases of intussusception and 146 cases of rotavirus infection were identified. The incidence of intussusception for infants younger than 1 year was 62/100,000 child-years. The age distributions of intussusception and rotavirus gastroenteritis overlapped, and a masculine predominance was noted in both cases. No significant association was observed between the monthly distribution of intussusception and rotavirus infection.

CONCLUSION

The present study has not convincingly shown that rotavirus diarrhea plays a major role in intussusception. However, data about age and sex distributions supported the biologic plausibility of such an association.

A high incidence of intussusception in Japan as studied in a sentinel hospital over a 25-year period (1978-2002)

The development of second-generation rotavirus vaccines requires knowledge of baseline incidence rates for intussusception in infants prior to vaccine introduction. To obtain such estimates we reviewed clinical records in a hospital that served as the major provider of paediatric beds in a local community in the northern part of Japan. During the 25-year period (1978-2002), there were 91 hospitalizations due to radiologically confirmed intussusception in children <5 years of age, of which 45% were <1 year of age. Assuming that all children with intussusception in the area had been admitted to this hospital, there were an average of 185 and 78 hospitalizations per 100000 person-years for children <1 year old and 5 years old respectively. There was period-to-period variability with no long-term secular trend in the incidence of intussusception. The incidence rate in Japan was among the highest thus far reported, providing further evidence of geographic variability.

A Hexavalent Human Rotavirus–Bovine Rotavirus (UK) Reassortant Vaccine Designed for Use in Developing Countries and Delivered in a Schedule with the Potential to Eliminate the Risk of Intussusception

There is an urgent need for a rotavirus vaccine, because up to 592,000 infants and young children <5 years old die each year from rotavirus diarrhea, predominantly in the developing countries. We have developed a tetravalent human-bovine rotavirus (UK) reassortant vaccine with VP7 (G) specificity for serotypes 1, 2, 3, and 4, which has been shown to be safe, immunogenic, and effective in preventing severe rotavirus diarrhea. However, because of the emergence of VP7 (G) serotype 9 as an epidemiologically important serotype and the importance of VP7 (G) serotype 8 in focal areas, we are planning to add human-bovine (UK) reassortants with G8 and G9 specificity to the tetravalent vaccine, thereby formulating a "designed" hexavalent vaccine for universal use. In addition, we propose that the vaccine be administered orally in a 2-dose schedule, with the first dose given at 0-4 weeks of age and the second dose given at 4-8 weeks of age, when infants are relatively refractory to developing intussusception, thereby avoiding the age period when naturally occurring intussusception is most prevalent (i.e., ages 3-4 months through age 9 months). In this way, there may be the potential to eliminate or at least significantly decrease the risk of intussusception associated with rotavirus vaccination.

Lack of association between rotavirus infection and intussusception: implications for use of attenuated rotavirus vaccines

BACKGROUND

Withdrawal of the tetravalent rhesus-human rotavirus vaccine Rotashield because of its association with intussusception raised concerns about a potential link between natural rotavirus disease and intussusception. Our objective was to determine whether such an association exists.

METHODS

In the Southern California Kaiser Permanente Health Care Plan, a large health maintenance organization, from October, 1992, to July, 1999, we retrospectively identified by computerized data and medical charts all children <3 years old with intussusception, and from 1997 to 1999 we independently identified by prospective clinical and laboratory evaluation children <3 years old with rotavirus diarrhea. We compared the epidemiologic characteristics of intussusception and rotavirus infection in our study population and evaluated for the presence of both diseases in individual patients.

RESULTS

Using computerized data we identified 124 cases of intussusception, 101 (81%) of which were confirmed by medical chart and radiologic reviews. The incidences for infants <1 year old and for children <3 years old were 41 (95% confidence interval, 32 to 55) and 17 (95% confidence interval, 13 to 20) per 100,000 child years, respectively. Between November 1997 and July 1999, we identified 470 cases of rotavirus diarrhea and none had intussusception. Although rotavirus diarrhea had a distinct peak incidence between December and February, intussusception had no apparent seasonality. The age distributions overlapped, but intussusception occurred at an earlier age than rotavirus disease.

CONCLUSIONS

We found no epidemiologic evidence for an association between intussusception and natural rotavirus infection, but our study was limited by an insufficient number of cases to definitively exclude a causal link. The dramatic winter peak of rotavirus disease had no discernable parallel in the incidence of intussusception. Our data suggest that the association between tetravalent rhesus-human rotavirus vaccine and intussusception may possibly result from the nonhuman rotavirus components of that vaccine.