Japan's vaccine service and an introduction to the history of cumulative vaccine coverage

During the measles epidemic periods in 1999-2003, a research group elaborated a method of estimating vaccination coverage. The objective of cumulative vaccination coverage (CVC) was to estimate the age of vaccine completion for vaccine targets in an age cohort. From randomly selected children of an age cohort, vaccine records including the date of birth and date of vaccine administration were retrieved, allowing for the calculation of the age of vaccine targets. By acquiring this information, it is possible to derive vaccination trends by age. According to the literature, CVC is now more widely applied and is used for monitoring delays of vaccination due to changes of the vaccine administration schedule and schedule interaction when newly-introduced vaccines are implemented. Although CVC is rather costly because it requires random sampling, we conclude that it is a useful method for estimating herd immunity.