Contents

21 Varicella (chickenpox)

21.5 Recommended immunisation schedule

Varicella vaccine can be administered at age 15 months with MMR, Hib and PCV13 vaccines. Because the risk of febrile seizures for those aged 12–23 months is higher following MMRV than MMR VV (see section 21.7), this dose should be administered as monovalent varicella vaccine. (This requires four injections at the 15-month visit.) For a second dose of varicella vaccine, or first doses after age 4 years, either VV or MMRV can be used.

Because New Zealand does not have a universal vaccination programme, chickenpox continues to circulate liberally in the community, providing boosting. For healthy children who have received varicella vaccine, a second dose is not essential if they were aged over 12 months but under 13 years when first vaccinated. Data from Japan indicates that when chickenpox continues to circulate at high levels, giving many opportunities for regular boosting of vaccine-induced immunity, protection lasts for at least 20 years.20 Varicella vaccine is voluntary in Japan and immunisation coverage was estimated to be around 20 percent. Antibody levels were higher at 20 years post-vaccination than at 10 years post-vaccination, confirming that boosting of immunity had occurred.20

21.5.1 Funded vaccine for high-risk groups

Two doses of varicella vaccine (Varilrix) are recommended and funded for the following groups (see also sections 4.2 and 4.3).

Table 21.1: High-risk groups eligible for funded varicella immunisation

Note: See the Pharmaceutical Schedule (www.pharmac.govt.nz) for the number of funded doses and any changes to the funding decisions.

High-risk groups funded for immunisation are:
  • non-immune patients:
with chronic liver disease who may in future be candidates for transplantation
– with deteriorating renal function before transplantation
– prior to solid organ transplant
– prior to any elective immunosuppression*
– for post-exposure prophylaxis of immune competent in-patients
  • patients at least 2 years after bone marrow transplantation, on the advice of their specialist
  • patients at least 6 months after completion of chemotherapy, on the advice of their specialist
  • HIV-positive patients who are non-immune to varicella, with mild or moderate immunosuppression, on the advice of an HIV specialist
  • patients with inborn errors of metabolism at risk of major metabolic decompensation, with no clinical history of varicella
  • household contacts of paediatric patients who are immune compromised or undergoing a procedure leading to immune compromise, where the household contact has no clinical history of varicella
  • household contacts of adult patients who have no clinical history of varicella and who are severely immune compromised or undergoing a procedure leading to immune compromise, where the household contact has no clinical history of varicella.
* Note that the period of immunosuppression due to steroid or other immunosuppressive therapy must be longer than 28 days.

21.5.2 Healthy infants and childrenTop

Varicella vaccine is not yet on the Schedule. One dose is, however, recommended for children from age 12 months to 12 years, inclusive.

21.5.3 Adolescents and adultsTop

Varicella vaccine in a two-dose schedule is recommended (but not funded) for the following groups:

See section 21.8.1 for information about assessing susceptibility.

21.5.4 Immunosuppressed individualsTop

The vaccine should not be given to immunosuppressed individuals except under the direction and care of a specialist, following a suitable protocol9 (see sections 4.2 and 4.3). Immunosuppressed individuals are at highest risk of severe varicella and zoster infections. The original vaccine formulations, in particular Varivax, have been studied in immunosuppressed children (most of whom were children with leukaemia in remission). Approximately 20 percent of these vaccine recipients required acyclovir because of a rash developing up to four weeks after vaccination. Despite this, the study concluded that the vaccine Varivax was safe, immunogenic and effective in these children.21, 22 The combination MMRV vaccine should not be used in immunosuppressed individuals.

Where immunosuppressed individuals cannot be vaccinated, it is important to vaccinate the household members and other close contacts (funded for household contacts) to provide ‘ring fence’ protection (see sections 4.2, 4.3 and 21.7). Immunisation of children with congenital T-cell immune deficiency syndromes is generally contraindicated, but those with impaired humoral immunity may be immunised (see below for further contraindications).

Health care workers

All health care workers on obstetric, paediatric and neonatal units, and those caring for immunosuppressed children and adults, should be immunised with varicella vaccine if they are susceptible to varicella. When a health care worker has a good history of prior varicella infection23 no blood test is required. If there is not a good history of varicella infection, a blood test to assess susceptibility will be necessary, as many individuals with no clinical history of varicella are immune (see below).

If a health care worker who has clinical contact with patients develops a rash as a result of the vaccine (around 5 percent), they must be excluded from contact with immunosuppressed or other at-risk patients and allocated other duties, or excluded from their place of work, for the duration of the rash. As varicella vaccine-induced immunity is less complete than following natural infection, when exposure to wild chickenpox occurs, previously vaccinated health care workers should examine themselves daily for a rash from days 10 to 21 after exposure. If a rash appears, they should seek advice from their occupational health service.