Varicella vaccination in children

Varicella vaccine is a lyophilised preparation which contains live attenuated organisms of the Oka strain of varicella zoster virus (1)

• should be administered as deep subcutaneous injection and can be given together with other live vaccines such as MMR
• children from one year to under 13 years of age; a single dose of varicella vaccine will give protection for around 90% of children
• children aged 13 years or older and adults - should receive two doses of varicella vaccine, four to eight weeks apart, around 75% will have protection against clinical chickenpox (1)

A critical review has examined the evidence relating to the use of varicella vaccination in children (2). In summary:

• studies included in the review were identified by searching Medline (1966 to 2000) with the terms chickenpox, vaccination, and human, and with methodological terms to retrieve high quality controlled clinical trials and cohort studies
• data was extracted on study design, patient characteristics, vaccine dose, length of follow-up and outcomes (effectiveness of vaccine, transmission of varicella, risk of herpes, adverse reactions)
  • vaccine effectiveness
    • assessed in 10 reports from 8 randomised controlled trials (RCTs)
      • 2 RCTs showed that a single dose of varicella zoster vaccination (VZV) was effective in preventing varicella
      • 1 showed 100% efficacy at 9 months
      • 1 showed 72% efficacy at 29 months
      • 3 dose-titration RCTS supported the efficacy of the VZV is protection against varicella infection
  • adverse reactions
    • assessed in 13 reports from 12 trials
      • of trials of children
        • none showed an increase in varicella-like rash or fever from VZV over placebo
      • injection site reactions ranged from 7% to 30%
      • adverse reactions were not related to vaccine dose
      • the risk of herpes zoster in vaccinated people was assessed by 1 RCT and no zoster occurred in vaccinated or placebo groups at 9 months
• the review concluded that the evidence from randomised controlled trials supports the effectiveness of varicella vaccination in children

The UK Joint Committee on Vaccination and Immunisation (JCVI) recommended that a universal varicella (chickenpox) vaccination programme should be introduced as part of the routine childhood schedule (3)

• should be a 2-dose programme offering vaccination at 12 and 18 months of age using the combined MMRV (measles, mumps, rubella and varicella) vaccine
• been shown in other countries which include varicella in their routine vaccination schedule, a 2-dose schedule is predicted to decrease the number of cases of varicella seen in childhood rapidly and dramatically
• programme will prevent severe cases of varicella, and other serious complications of varicella, which while rare may have otherwise resulted in hospitalisation or other serious outcomes
• using the combined MMRV vaccine as a first dose has been associated with a slightly increased rate of febrile seizures when compared with using separate MMR and varicella vaccines at the same visit
  • although there is an increased risk of febrile seizures occurring when using the MMRV as the first dose, the absolute risk is very low
    • CDC estimates that one additional febrile seizure is seen for every 2,300 doses given compared with using separate vaccines
  • increased rate has not been observed when using the combined MMRV vaccine as a second dose

A catch-up programme should also be initiated following implementation of a programme to prevent a gap in immunity.

Reference:

• (1) Department of Health 2006. The green book - Varicella
• (2) Skull SA, Wang EE. Varicella vaccination - a critical review of the evidence. Arch Dis Child 1001;85:83-90
• (3) JCVI statement on a childhood varicella (chickenpox) vaccination programme (November 14th 2023).