Live attenuated varicella vaccination in immunocompromised children

Abstract

Live attenuated varicella vaccine (OKA strain) was administered to 42 children ranging in age from three to 13 years, they consisted of nine controls, 21 children on chemotherapy for acute leukaemia and lymphoma, and 12 children receiving steroid treatment. The immunisation was performed without suspending the administration of immunosuppressive agents in an attempt to stop the spread of varicella infection that was occurring at the time in the pediatric ward. After vaccination, seven immunocompromised children developed clinical varicella within 16-41 days. The symptoms were mild to moderate in all except one who had severe disseminated clinical symptoms. The attempt to isolate and identify vaccine virus markers in these patients was not successful, but there was no further spread of varicella in the paediatric ward. The overall seroconversion rate as determined by immune adherence haemagglutination test was found in 85 per cent of the vaccinees at three months after vaccination and significant antibody level persisted for 15 months in 60 per cent of them. Children with acute leukaemia and lymphoma had a good antibody response (93.3%) which was similar to that of normal children (75%) even without suspending cytotoxic drugs at the time of vaccination. Poorer antibody response (50%) was found in children who received steroid treatment. Positive skin test to varicella antigen was found in 50 per cent of the vaccinees at one month after vaccination; it declined to 31.5 per cent at six months. Only 6.2 per cent of the vaccinees had a positive skin reaction at 9-12 months. It was concluded that live attenuated varicella vaccine (OKA strain) is sufficiently safe and immunogenic in immunocompromised children even without suspending immunosuppressive agents at the time of vaccination. In addition, this vaccine was found to be effective for preventing the spread of varicella in the paediatric ward.