Why is the zoster (varicella-zoster) vaccine recommended for individuals who have never had varicella (chickenpox) before?

Zoster Vaccination for Individuals Without Prior Varicella Infection

Zoster vaccination is recommended for adults aged 50 years and older who have no history of varicella or unclear history of varicella, with a preference for the recombinant zoster vaccine (RZV), as it has been shown to be safe and immunogenic in varicella zoster virus (VZV)-seronegative individuals. 1

Rationale for Vaccination Without Prior Varicella

• Both live zoster vaccine (ZVL) and recombinant zoster vaccine (RZV) have demonstrated safety and immunogenicity in VZV-seronegative individuals, making screening for prior varicella unnecessary before administering zoster vaccination 1

• The US CDC, Canadian, and German guidelines all recommend against screening for varicella history or conducting laboratory testing for serologic evidence of prior varicella when vaccinating immunocompetent adults aged 50 years and older 1

• This recommendation is supported by high seroprevalence studies showing that the majority of adults have been exposed to VZV, even if they don't recall having chickenpox 1

• There are no known safety risks associated with administering zoster vaccines to individuals susceptible to VZV 1

Evidence Supporting Safety in VZV-Seronegative Individuals

• A small study of 21 healthy adults aged 30 years who were either seronegative for VZV or had low VZV antibody titers showed that ZVL was both immunogenic and well-tolerated 1

• Another small study conducted in 23 VZV-seronegative transplant patients demonstrated that RZV was both safe and immunogenic 1

• Before administration of zoster vaccine, patients do not need to be asked about their history of varicella (chickenpox) or have serologic testing conducted to determine varicella immunity 2

Special Considerations for Known VZV-Seronegative Individuals

• For persons who are known to be seronegative for VZV, immunization with 2 doses of varicella vaccine with an interval of 4 weeks is suggested 1

• Australian immunization guidelines suggest that adults who are VZV-seronegative and have no history of age-appropriate varicella vaccination may receive either 2 doses of varicella vaccine (preferable) or 1 dose of ZVL (if aged 50 years or older) 1

• For immunocompromised adults aged under 50 years, a history of varicella vaccination and serology testing should be considered before administering RZV vaccination 1

Recommendations for Different Population Groups

• For immunocompetent adults aged 50 years and older:

  • No screening for varicella history is necessary 1
  • Either ZVL or RZV can be administered, with RZV being preferred due to higher efficacy 1

• For immunocompromised individuals:

  • Healthcare providers should consider factors such as age, documentation of prior varicella or vaccination, and serology testing results 1
  • RZV is preferred as ZVL (being a live vaccine) is contraindicated in immunocompromised patients 3

Clinical Pitfalls to Avoid

• Don't assume that absence of recalled chickenpox history means the person is VZV-seronegative, as most adults have been exposed to VZV even without clinical disease 1

• Don't unnecessarily delay zoster vaccination to conduct varicella serology testing in immunocompetent adults aged 50 years and older 1

• Don't administer ZVL (live vaccine) to immunocompromised patients, even if they are VZV-seronegative 3

• Don't miss the opportunity to vaccinate older adults against zoster, as the risk of reactivation increases with age regardless of whether they recall having had chickenpox 2, 4