Varicella zoster virus (VZV) is a herpes virus that causes primary infection (chickenpox) and reactivation (shingles) after establishing latency within neurons. The rate of VZV seronegativity amongst HIV positive patients in the UK was 1.5%, with those acquiring primary infection more likely to present with severe disease (49). The incidence rate of shingles in HIV positive individuals remains 3-5 times higher than in HIV negative controls in the ART era, associated with low CD4+ T cell counts and high HIV viral loads. HIV-infected individuals have a higher incidence of cutaneous, neurological and visceral complications (50).
Chickenpox vaccine
This is a live attenuated vaccine using the Oka strain of VZV, which can reactivate to cause shingles (although less commonly than wild type virus). It is not recommended for patients with a CD4+ T cell count of <200/mL. In nonimmune (VZV IgG antibody negative) HIV positive individuals with a CD4+ T cell count of >200/mL, vaccination should be considered based on safety and immunogenicity data obtained from HIV positive children (51). Two doses are recommended given 3 months apart. The combination MMRV vaccine is not recommended.
Shingles vaccine
The currently available vaccine is a more potent high-titre live attenuated vaccine designed to boost natural immunity and reduce the incidence of shingles and post herpetic neuralgia in people >50 years of age. Two doses were found to be safe and immunogenic in a trial of HIV-positive patients with CD4+ T cell counts >200/mL (52), and should be considered in those patients with CD4+ T cell counts >200-350 /mL with serological confirmation of previous VZV infection. A new zoster vaccine consisting of recombinant viral proteins has shown safety and efficacy in a cohort of HIV positive patients, including a small number with CD4+ T cell counts between 50-200/μL (53).