Primary prevention
While varicella immunisation is routine in the US, in Europe the use of varicella vaccine varies between countries.[19]
In the UK and in some other parts of Europe, the varicella vaccine is not currently recommended for routine use in children. However, it is recommended to protect those at risk of serious illness by immunising individuals who are in regular or close contact with these patients, such as non-immune healthcare workers and healthy susceptible close household contacts of immunocompromised patients.[20]
In the US, two preparations of live, attenuated varicella-zoster virus (VZV)-containing vaccines are available for prevention of varicella: a single-antigen varicella vaccine (VAR) for use in healthy children (aged 12 months and over), adolescents, and adults; and a combination measles, mumps, rubella, and varicella vaccine (MMRV) for use in healthy children aged 12 months to 12 years. Vaccination guidelines in the US recommend a routine 2-dose varicella vaccination program for children, with the first dose administered at 12 to 15 months of age and the second dose at 4 to 6 years.[21][22] For the first dose, the US guidelines recommend that the MMR and varicella vaccines are administered separately in children aged 12-47 months.[22] Routine vaccination (2 doses, 4 to 8 weeks apart) of all healthy adults without evidence of immunity is also recommended (or a second dose if they have received only 1 dose).[23] Vaccination is contraindicated in pregnant women.[23] Vaccination may be considered in patients with HIV infection with CD4 percentages ≥15% and CD4 count ≥200 cells/mm³ with no evidence of immunity (2 doses, 3 months apart); note that VAR is contraindicated in those with HIV infection with CD4 percentage <15% or CD4 count <200 cells/mm³.[23]
While a single dose has about 80% to 85% effectiveness, the currently recommended second dose increases effectiveness to over 95%.[24][25][26][27][28] Clinical trials to assess the effectiveness of the vaccine typically follow patients in the short term (1- to 2-year follow-up). Protective concentrations of antibody among immunised people in Japan have been shown to persist for more than 20 years after immunisation, and in one long-term study the estimated proportion of vaccine recipients who remained varicella-free at the end of 7 years was 95%.[24][29] Another study of 10-year follow-up by the same group demonstrated an estimated vaccine efficacy for the 10-year observation period of 94.4% for 1 injection and 98.3% for 2 injections.[25] A Cochrane review found the MMRV (measles, mumps, rubella, varicella) vaccine to be 95% effective at preventing varicella after two doses in children aged 11 to 22 months in a 10-year follow-up.[30]
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Implementation of universal immunisation strategies has also been shown to significantly decrease varicella-associated deaths.[31]
Some countries have not recommended routine childhood varicella vaccination, in part due to concerns that decreases in exogenous boosting from natural infection (i.e., children with varicella) will lead to increased risk for herpes zoster in adults.[32][33] In Europe, varicella vaccination recommendations remain heterogeneous, with only 7 European Union countries recommending universal vaccination.[34] Retrospective studies have shown conflicting results, and have been limited by notable increases in herpes zoster prior to the implementation of such childhood vaccination programmes.[35][36][37][38]
The live vaccine is contraindicated in neonates, pregnant women, and immunocompromised individuals or those receiving high-dose systemic immunosuppressive therapy; however, in some countries, vaccination is recommended for all non-immune women as part of pre-pregnancy and postpartum care.[39] Varicella immunity status and history of vaccination should be documented in all pregnant women, and all seronegative patients should be counselled about the increased risk of primary varicella in pregnancy and the need to seek immediate medical help in the case of possible exposure.[40] The vaccines are also contraindicated in patients with a history of hypersensitivity to any component of the vaccines, including gelatin, or a history of anaphylactoid reaction to neomycin. Additional contraindications should be noted and additional precautions taken for children receiving a combination vaccine (measles, mumps, rubella, and varicella vaccine).[41]
In non-randomised studies, varicella vaccine appears to be safe in some patients with organ dysfunction and low levels of immunosuppression.[42][43][44][45][46][47] Reviews of recommendations for the use of varicella vaccines in high-risk transplant populations are also available.[48][49] Patients with leukaemia, lymphoma, or other malignancies whose disease is in remission and whose chemotherapy has been terminated for at least 3 months can receive live-virus vaccines. When immunising patients in whom some degree of immunodeficiency might be present, only single-antigen varicella vaccine should be used. Immunisation of leukaemic children who are in remission or of other immunocompromised hosts who do not have evidence of immunity to varicella should be undertaken only with expert guidance and with the availability of antiviral therapy should complications ensue.[21]
In some countries, it is recommended that varicella-zoster immunoglobulin should be administered to all neonates born to mothers who developed the disease between 5 days before and 2 days after delivery, as these infants are at risk for severe disseminated varicella.[50][51]
Secondary prevention
Post-exposure prophylaxis through use of varicella vaccine, immunoglobulin, or antivirals is recommended for some patients following exposure to a person with acute varicella zoster or herpes zoster.
Varicella immunisation:
US guidelines recommend administering varicella vaccine to healthy people without evidence of immunity who are aged 12 months or older (including adults), as soon as possible after exposure, preferably within 3 days and up to 5 days.[41] Effectiveness has been demonstrated to be more than 90% when given within 3 days of exposure, and about 70% at 5 days.[21]
Passive immunoprophylaxis:
UK guidelines recommend use of varicella-zoster immunoglobulin (VZIG) for susceptible individuals who are unable to take oral antivirals, and for susceptible neonates exposed within one week of delivery (in utero or post-delivery).[129]
US guidelines recommend use of varicella-zoster immunoglobulin (VariZIG) for high-risk patients who do not have evidence of varicella immunity and in whom varicella immunisation is contraindicated.[41][49][51][130][131][132] Specific groups where VariZIG is recommended include:[41][130]
Immunocompromised patients
Neonates whose mothers have signs and symptoms of varicella around the time of delivery (i.e., 5 days before to 2 days after)
Premature infants born at ≥28 weeks of gestation who are exposed during the neonatal period and whose mothers have no evidence of immunity to varicella
Premature infants born at <28 weeks of gestation or who weigh ≤1 kg at birth and were exposed during the neonatal period, regardless of their mothers' evidence of immunity to varicella
Pregnant women without evidence of immunity.
VariZIG should be given as soon as possible and within at least 10 days of exposure.[41][51] Patients eligible for the varicella vaccine should have the immunisation delayed by 5 months after administration of VariZIG.[21]
Intravenous immunoglobulin (IVIG) is an alternative option when varicella-zoster immunoglobulin can not be used.[41][129]
Antiviral prophylaxis
In the UK, antivirals are now recommended for post-exposure prophylaxis for all at-risk groups (apart from susceptible neonates).[129] Antivirals are given from day 7 to day 14 after exposure.
US guidelines note that pre-emptive antiviral therapy may be used in select patients if VariZIG and IVIG are not available.[41]
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