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Live attenuated varicella virus vaccine. Efficacy trial in healthy children
Insights
The Oka/Merck varicella vaccine demonstrated 100% efficacy in preventing chickenpox (varicella) in healthy children aged 1-14 years. This live attenuated vaccine was well-tolerated with no observed viral spread.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Varicella (chickenpox) is a common childhood viral illness.
- Effective vaccination strategies are crucial for preventing disease spread and complications.
Purpose of the Study:
- To evaluate the efficacy and safety of the live attenuated Oka/Merck varicella vaccine.
- To assess the immunogenicity of the varicella vaccine in susceptible children.
Main Methods:
- A double-blind, placebo-controlled trial involving 956 children aged 1-14 years.
- Serological confirmation of susceptibility and antibody detection post-vaccination.
- Nine-month surveillance for varicella cases.
Main Results:
- The vaccine was well-tolerated with minimal clinical reactions.
- 94% of vaccinated children developed detectable antibodies.
- 100% efficacy in preventing varicella; all 39 cases occurred in the placebo group.
Conclusions:
- The Oka/Merck varicella vaccine is highly efficacious and safe for preventing chickenpox in healthy children.
- The vaccine induces a robust antibody response, conferring complete protection against varicella infection.
Abstract:
We conducted a double-blind, placebo-controlled efficacy trial of the live attenuated Oka/Merck varicella vaccine among 956 children between the ages of 1 and 14 years, with a negative clinical history of varicella. Of the 914 children who were serologically confirmed to be susceptible to varicella, 468 received vaccine and 446 received placebo. The vaccine produced few clinical reactions and was well tolerated. There was no clinical evidence of viral spread from vaccinated children to sibling controls. Approximately eight weeks after vaccination, 94 per cent of the initially seronegative children who received vaccine had detectable antibody to varicella. During the nine-month surveillance period, 39 clinically diagnosed cases of varicella, 38 of which were confirmed by laboratory tests, occurred among study participants. All 39 cases occurred in placebo recipients; no child who received vaccine contracted varicella. The vaccine was 100 per cent efficacious in preventing varicella in this population of healthy children (P less than 10(-9).