Clinical Trials of Rotavirus Vaccines

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Abstract
The clinical efficacy of candidate rotavirus vaccines has been tested in Tampere, Finland, over four winter and spring rotavirus epidemic seasons in 1983-1986. Testing against natural challenge has demonstrated that heterologous oral rotavirus vaccines induce cross-protection to human rotavirus diarrhoea. The trials have also given insight into mechanisms of protection in human rotavirus diarrhoea. After the oral vaccination of infants aged six to 12 months the highly attenuated bovine rotavirus strain RIT 4237, titre 10(8) per dose, probably 'takes' in most vaccinees, producing a symptomless intestinal infection with a low virus excretion rate and an antibody response in over 80% of the initially seronegative subjects. Upon natural challenge such vaccination gives no protection against human rotavirus infection but gives 50-60% protection against any clinically detectable rotavirus-associated illness and 80-90% protection against severe rotavirus diarrhoea, regardless of the infecting human rotavirus serotype. The less attenuated rhesus monkey rotavirus RRV-1, titre 10(5)-10(6) per dose, is more infectious in humans, and virus multiplication in the intestine results in excretion of vaccine virus in the stools and some clinical symptoms, mainly fever, 3-4 days after vaccination. The degree of protection against human rotavirus diarrhoea appears similar to that induced by bovine rotavirus vaccine.