Published: 2 September 2015


Varicella Zoster Virus Vaccines — Medication Errors

This article is more than five years old. Some content may no longer be current.

Prescriber Update 36(3): 40
September 2015

Key Messages

  • Healthcare professionals should take care when preparing and administering varicella zoster vaccines to ensure the correct product is administered.
  • Mix ups between the paediatric (Varilrix and Varivax) and adult (Zostavax) formulations have recently occurred.
  • Zostavax contains a much higher titre of the virus than Varilrix and Varivax and has the potential to cause harm when administered to children.
  • Healthcare professionals should consider risk mitigation strategies to prevent future errors.

Healthcare professionals should take care when prescribing, preparing and administering Zostavax, Varivax or Varilrix to ensure the correct varicella zoster virus vaccine is administered. The New Zealand Pharmacovigilance Centre has received five reports of medication error involving administration of the incorrect varicella zoster virus vaccine to a child or adult.

The Centre for Adverse Reactions Monitoring (CARM) has received four reports and the newly established Medication Error Reporting Programme (MERP) has received one report. In four of the five reports, children were administered Zostavax in error. In the fifth case, an elderly patient was prescribed and administered Varilrix for the prevention of shingles.

Varicella zoster virus is responsible for both chickenpox (varicella) and shingles (herpes zoster). Chickenpox is the primary infection and most commonly occurs in children. Shingles occurs when latent varicella zoster virus is reactivated and is more common in older adults1.

In New Zealand, three varicella zoster virus vaccines are approved and available. Two of these, Varilrix and Varivax are used to vaccinate against chickenpox and can be used from ages nine and 12 months respectively2,3. The third, Zostavax is used for the prevention of shingles in individuals 50 years of age and above4.

Zostavax contains a much higher titre of the virus than Varilrix and Varivax and has the potential to cause harm when administered to children. It is not recommended for use in the paediatric population4.

To reduce the risk of medication errors, consider the following strategies:

  • separate storage of Zostavax and other adult vaccines from childhood vaccines
  • implementing independent double check procedures prior to vaccine administration
  • alerting staff to the differences in the various products.

In cases where the correct product is not available, the patient should be asked to return at a time when the correct product will be available.

Healthcare professionals are encouraged to report to CARM or MERP (anonymously if preferred) any actual or potential ‘near miss’ medication errors (

Information on the approved indication(s) as well as correct dosing and administration of each product can be found in the respective data sheets, available on the Medsafe website (

  1. Immunisation Advisory Centre. 2014. Chickenpox (Varicella) Fact Sheet. URL: (accessed 9 July 2015).
  2. GlaxoSmithKline NZ Ltd. 2014. Varilrix Data Sheet. 18 October 2014. URL: (accessed 9 July 2015).
  3. Merck Sharp and Dohme (New Zealand) Limited. 2013. Varivax Data Sheet. 7 November 2013. URL: (accessed 9 July 2015).
  4. Merck Sharp and Dohme (New Zealand) Limited. 2015. Zostavax Data Sheet. 29 April 2015. URL: (accessed 9 July 2015).
Hide menus
Show menus
0 1 2 4 5 6 7 9 [ /