Contents

21 Varicella (chickenpox)

21.4 Vaccines

21.4.1 Available vaccines

There are two live attenuated monovalent varicella vaccines (VV) registered (approved for use) and available (marketed) in New Zealand. One quadrivalent live attenuated measles-mumps-rubella-varicella (MMRV) vaccine is registered but not currently available in New Zealand. Varicella-containing vaccines are not on the Schedule, but VV is recommended and funded for certain high-risk groups (see section 21.5.1).

Funded vaccine

Monovalent varicella vaccine (Varilrix, GSK): contains no less than 103.3 PFU (plaque-forming units) of the varicella virus (Oka strain). Other components and residuals include amino acids, human albumin, lactose, neomycin sulphate and polyalcohols.

Other vaccines

21.4.2 Efficacy and effectivenessTop

Single-dose varicella vaccination programmes have had a dramatic impact on the incidence of VZV infections,11–13 hospitalisations1, 2, 14 and serious outcomes,3 particularly when high coverage rates are achieved. Indirect effects are also apparent. However, single-dose programmes are associated with outbreaks even among highly vaccinated groups.9 The use of a second dose during outbreaks has been an effective strategy to prevent further cases; catch-ups in non-immunised groups without a previous history of varicella are also important.

There is a significant reduction in breakthrough disease when two doses are given. After a second dose in children the immune response is markedly enhanced, with over 99 percent of children attaining an immune response thought to provide protection, and the geometric mean antibody titre is also significantly increased. Over a 10-year period the estimated vaccine efficacy of two doses for prevention of any varicella disease is 98 percent (compared to 94 percent for a single dose), with 100 percent efficacy for the prevention of severe varicella. The likelihood of breakthrough varicella is reduced by a factor of 3.3.15, 16 Because of this data, in 2006 the US authorities recommended a two dose strategy for varicella prevention, with the first dose at age 12–15 months and the second at age 4–6 years, as for MMR.9, 15

The antigenic components of MMRV vaccines are non-inferior compared with simultaneous administration of MMR and varicella vaccines,17, 18 for both the first and second doses.

Duration of immunity

Varicella vaccination provides long-term but probably not lifelong immunity against VZV, in contrast to VZV natural infection. Long-term studies are needed in countries with universal vaccine programmes to assess the duration of the immune response and protection from varicella in the absence of external boosting from exposure to wild-type virus.17

21.4.3 Transport, storage and handlingTop

Transport according to the National Guidelines for Vaccine Storage and Distribution.19

Monovalent VV and MMRV vaccines require reconstitution before administration.

21.4.4 Dosage and administrationTop

The dose of monovalent VV and MMRV vaccine is 0.5 mL, administered by subcutaneous injection in the deltoid area (see section 2.3).

Co-administration with other vaccines

Monovalent VV or MMRV vaccine can be administered concurrently with other vaccines, but in a separate syringe and at a different site. If not administered concurrently, the vaccine must be separated from other live vaccines (eg, MMR, BCG) by at least four weeks.