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Live varicella vaccine in severely immunodepressed children
Insights
This study evaluated the varicella vaccine in immunocompromised children. While antibody responses were acceptable, they were lower and shorter-lasting than in healthy individuals, suggesting a need for booster doses.
Area of Science:
- Immunology
- Vaccinology
- Pediatric Oncology
Background:
- Severely immunocompromised children undergoing chemotherapy often have impaired immune responses.
- Varicella-zoster virus (VZV) infection poses a significant risk to these patients.
Purpose of the Study:
- To assess the immunogenicity and safety of a live attenuated Oka-strain varicella vaccine in children with acute leukemia or solid tumors.
- To evaluate the antibody response and protection against varicella disease in this vulnerable population.
Main Methods:
- 45 immunocompromised children received a single subcutaneous dose of varicella vaccine.
- Immunological parameters were assessed before and after vaccination.
- Serological testing measured varicella antibodies at multiple time points post-vaccination.
- Clinical outcomes, including breakthrough varicella cases, were monitored.
Main Results:
- 70% of initially seronegative children developed antibodies by 1 month, decreasing to 40% by 12 months.
- Immunological parameters did not predict antibody response to the vaccine.
- 18% of children developed varicella post-vaccination, with some cases linked to the vaccine virus.
- Antibody response and protection were lower and shorter-lasting compared to healthy subjects.
Conclusions:
- The varicella vaccine provides acceptable, though diminished, protection in severely immunocompromised children.
- Booster doses may be necessary at shorter intervals for sustained immunity in this population.
- Further research into optimal vaccination strategies for immunocompromised pediatric patients is warranted.
Abstract:
One dose containing 3,100 PFU of a live attenuated Oka-strain varicella vaccine (Varilrix, Smith Kline-RIT, Belgium) was administered subcutaneously to 45 children, 26 of whom were suffering from acute leukaemia and 19 from solid malignant tumours. Their immunological status had been severely compromised by chemotherapy as evidenced by markedly low values for all immunological parameters. Of the 31 children seronegative for varicella at the time of vaccination, 70%, 85%, 75%, and 40% had varicella serum antibodies at 1, 2, 3, and 12 months after vaccination, respectively. Evaluation of the immunological parameters indicated that they were of no predictive value regarding the antibody response of the patients to the vaccine. Eight children (18%) developed varicella after vaccination. In one case, the disease was caused by the vaccine virus while in another, the vaccine virus was probably also responsible. The remaining six cases were caused by wild virus. The antibody response and accompanying protection against disease induced by the vaccine in severely immunodepressed patients is acceptable, but clearly lower and of shorter duration than in normal subjects. Thus, in immunocompromised patients, booster doses of the vaccine may be required at relatively short intervals.