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Each year it is estimated that group A rotavirus infection causes around 800 000 deaths worldwide from gastroenteritis in children under 5 years of age.1 Symptoms usually accompany primary infection, which is followed by protection against subsequent symptomatic infection.2 For this reason, the peak attack rates for symptomatic rotavirus disease occur in children between 6 and 12 months of age.3
The development of rotavirus vaccines has focused mainly on the use of orally administered live attenuated rotaviruses from non-human hosts. A recent modification was the production of tetravalent vaccines containing “reassortant” strains of rotavirus (TV-RRV).4 These reassortants contain 10 genes from rhesus monkey strains and one gene that codes for human serotypes G1, G2, and G4; the rhesus rotavirus itself provides coverage for serotype G3.4 Efficacy studies in the USA, Finland, and Venezuela have demonstrated that TV-RRV provides good protection against severe rotavirus diarrhoea.5-7 In the USA, TV-RRV is now recommended for routine use by both the Advisory Committee on Immunizations Practices8 and the American Academy of Pediatrics.9 In spite of acknowledged need, the high cost of this vaccine puts it beyond the scope of most developing countries.10 In the developed world, however, TV-RRV is expected to be highly effective at preventing morbidity and mortality due to severe rotavirus diarrhoea, and could have a substantial economic impact from savings on the direct medical and social costs of caring for such children.11 12 The vaccine is currently going through licensing by the European Medicines Agency, and in the UK we will shortly have to decide whether the vaccine should be incorporated into our infant programme.
Before a decision on whether to introduce mass vaccination in the UK, estimates of the morbidity and mortality from rotavirus infection are required. One of the potential benefits of rotavirus vaccination would be to reduce the large numbers of admission for gastroenteritis each year. Unfortunately, it is difficult to estimate the annual numbers of admissions due to rotavirus from routine data in the UK. Hospital admissions are coded under the ninth revision ofInternational Classification of Diseases(ICD-9), which has no specific code for rotavirus infection. In addition, as laboratory investigation is not always performed, routine data will always underestimate the true numbers of admissions due to rotavirus.13 To circumvent this, weekly data on laboratory confirmed infections and hospitalisations in North Thames were used to estimate admissions attributable to rotavirus during the winter seasonal increase of 1993–94.14 This approach suggested that rotavirus is responsible for about 17 810 admissions each year in the UK—five admissions for every 1000 children under 5 years of age. To help confirm these findings, prospective hospital and community studies are underway in various parts of the UK.
A case series from Canada,15 and the excess of deaths from gastroenteritis in the winter in USA and Australia,16 17 suggest that rotavirus can lead to death by dehydration in the developed world. In the USA, however, deaths from childhood diarrhoea have fallen in the past two decades17and the number of such deaths are now very small in the UK.14
The present vaccine is designed to confer protection to severe disease with serotypes G1–G4, which are responsible for more than 90% of group A rotavirus infections in the developed world.18More recent work, however, suggests a wider diversity,19indicating the need for a systematic study before and after the introduction of vaccination: such a study is currently being coordinated by the Public Health Laboratory Service. Rotaviruses can evolve by genetic drift and genetic shift, and the possibility of zoonotic infection and of natural reassortment between animal and human strains has been suggested.20 No evidence of genetic change was found during the vaccine trials,21 but if high coverage is achieved, it is conceivable that the selection of rotavirus serotypes for which the vaccine is less effective may occur. As the vaccine protects poorly against mild or asymptomatic infection, endemic strains are expected to continue to circulate. For this reason, “escape” strains are unlikely to become established following the implementation of mass vaccination. Whether this assumption is correct should be answered within the next few years by the experience with mass vaccination in the USA.
As oral rotavirus vaccine can be given at the same time as diphtheria–tetanus–polio–Haemophilus influenzae type b and oral polio vaccine, mass vaccination could be relatively easy to implement in the UK. A substantial reduction in morbidity from childhood gastroenteritis would be expected, although the impact on mortality in the UK is likely to be limited. As parental perceptions of the severity of disease has always been a strongly associated with high coverage of vaccination,22 there has been concern that the vaccine would not be acceptable to UK parents. For the past two years, the Health Education Authority has been exploring parental attitudes to new vaccines as part of its regular research programme. Perhaps surprisingly, 70–75% of the mothers of children under 3 years old reported that they would probably or definitely be likely to have their child immunised (S Davis and Z Bozoky, personal communication, 1999). The task now is to establish the cost–benefit of vaccine introduction for the UK to convince the health care professionals and the vaccine policy makers.
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