thats the same with varicella vaccine, it doesn't give 100% protection, but it does protect you sometimes from full blown or severe chickenpox. also doesnt stop viremia which leads to varicella becoming latent in you ganglia from a wild type infection. varicella is one of those viruses that is wierd with vaccines. mostly because it infilitrates your nerves quite quickly when you get chickenpox, and nerves arnt targeted by the immune system, plus varicella has tricks that could evade the immune system, unlike covid, hence why most herpes can lie dormant in different cell types(depending on the virus).