Varicella caused by the primary infection of a ubiquitous neurotropic human alpha-herpesvirus, varicella-zoster virus (VZV), exerts a considerable disease burden worldwide. The current live Varicella Vaccine Strain (vOka) is generally safe and effective. However, vOka retains full ability to cause mild varicella, establish latency and reactivate to cause herpes zoster that is often clinically indistinguishable from wild-type disease in vaccine recipients. These adverse effects could be the result from vOka haplotypes carrying the disease-causing alleles, raising safety concerns. Therefore, there is a need for next-generation varicella vaccines with reduced pathogenic risk to improve the current strategy for establishing worldwide herd immunity against this disease.
