The safety profile of varicella vaccine: a 10-year review
Susan A Galea1, Ann Sweet, Paul Beninger
1Merck Research Laboratories, Clinical Risk Management and Safety Surveillance, North Wales, Pennsylvania 19454-1099, USA. susan_galea@merck.com
Insights
The 10-year safety profile of Varivax, a live attenuated varicella vaccine, shows it is generally safe and well-tolerated. Postmarketing surveillance and PCR analysis confirm vaccine effectiveness and identify VZV strains in rare adverse events.
Area of Science:
- Vaccinology
- Virology
- Public Health
Background:
- Varivax is a live attenuated varicella vaccine (varicella virus vaccine live [Oka/Merck]) indicated for individuals 12 months and older.
- Postmarketing surveillance is crucial for assessing the long-term safety of vaccines.
- Polymerase chain reaction (PCR) analysis aids in identifying the specific VZV strains involved in post-vaccination events.
Purpose of the Study:
- To describe the 10-year safety profile of Varivax using global postmarketing surveillance data.
- To analyze the VZV strains associated with adverse events following Varivax vaccination.
- To evaluate the occurrence and characteristics of breakthrough varicella and herpes zoster.
Main Methods:
- Utilized data from global postmarketing surveillance reports submitted to Merck.
- Employed a Varicella Zoster Virus Identification Program using PCR analysis on selected specimens.
- Analyzed 16,683 voluntary reports and 697 herpes zoster reports.
Main Results:
- Overall reporting rate was 3.4 reports per 10,000 doses distributed.
- Wild-type VZV was identified in early rashes (<2 weeks post-vaccination); Oka VZV was associated with later rashes (15-42 days).
- Breakthrough varicella (>42 days) and some herpes zoster cases were linked to wild-type VZV; no primary neurologic events linked to Oka VZV.
Conclusions:
- Varivax demonstrates a generally safe and well-tolerated 10-year safety profile.
- PCR analysis helps differentiate between vaccine-derived and wild-type VZV in post-vaccination rashes.
- Rare instances of secondary transmission of Oka VZV and disseminated disease in immunocompromised individuals were noted.
Abstract:
Varivax (varicella virus vaccine live [Oka/Merck]; Merck), a live attenuated varicella vaccine, is indicated for vaccination against varicella in appropriate individuals > or =12 months of age. The 10-year safety profile for Varivax is described using data submitted to Merck from routine global postmarketing surveillance, combined with information from a Varicella Zoster Virus Identification Program, which uses polymerase chain reaction (PCR) analysis to identify the presence and strain of VZV in selected specimens. There were 16,683 reports worldwide voluntarily submitted to Merck, for an overall reporting rate of 3.4 reports/10,000 doses of vaccine distributed. PCR analysis of vesicular rashes that occurred within the first 2 weeks after vaccination was more likely to identify wild-type varicella-zoster virus (VZV), whereas the presence of Oka VZV was generally associated with vesicular rashes that occurred 15-42 days after vaccination. Reports of breakthrough varicella that occurred >42 days after vaccination were associated with wild-type VZV. Among 697 herpes zoster reports, PCR analysis identified Oka VZV in 57 reports and wild-type VZV in 38 reports. There were no primary neurologic adverse events associated with Oka VZV. Secondary transmission of Oka VZV from vaccine recipients with postvaccination vesicular rashes was identified in 3 susceptible household contacts. Disseminated Oka VZV was identified in 6 immunocompromised patients and 1 patient with Down syndrome. This review has shown that the vaccine is generally safe and well tolerated.
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