How long does vaccine-induced protection last?
The evidence currently suggests that the vaccine usually remains protective for at least 10 years after immunisation, although the proportion of protected people may decline gradually after the first few years. Protective levels among many children vaccinated in Japan have persisted more than 20 years after vaccination.9 However, studies into the duration of effectiveness have assessed the vaccine in an environment where wild varicella zoster virus infections and natural boosting of immunity are common. Significant boosting of the varicella immune response has been reported after second injections given 4–6 years after the initial immunisation.17 However, booster doses are not currently recommended. As the use of varicella zoster virus vaccine increases and exposure to wild-type virus decreases in the community, it is possible that the duration of protection may decrease. Should this prove to be the case, a booster dose of vaccine may be warranted.
