The effect of prior inoculation with an enterovirus (LEV 4) on rhinovirus infection of volunteers

Twenty-four volunteers at the Common Cold Unit were divided into two groups of twelve. One group was vaccinated orally with an enterovirus (LEV 4) and the other with nutrient broth. Both groups were challenged three days later with intranasal rhinovirus 4 and they were observed clinically and monitored by laboratory tests to see if any modification of the rhinovirus infection occurred. All the vaccinated volunteers were successfully infected with LEV 4 and were excreting the enterovirus in the faeces at near maximum titres at the time of the rhinovirus infection, following which 67 per cent of the volunteers were infected and 29 per cent developed symptoms. However, the vaccinated group did not differ from the unvaccinated in respect of the illness induced, the excretion of rhinovirus type 4 or the rise of RV 4 antibody titre. LEV 4 was isolated from the nasopharynx of some of the volunteers, but the rhinovirus infection was not modified even in these. Interferon was present in the serum and nasal washings of nine volunteers in all, of whom only 3 had received the LEV 4 vaccination. Two additional volunteers were shown to be insusceptible to reinfection with LEV4. It was concluded that live enterovirus vaccination does not induce viral interference.