Changes in COPD mortality rate after amendments to the Preventive Vaccination Law in Japan

The Japanese government amended the Preventive Vaccination Law in November 2001 to specify elderly people aged ≥ 65 years as the target population for influenza vaccinations. The vaccine coverage among this age group rapidly increased thereafter. Our goal was to evaluate how this amendment affected the nationwide mortality rate of chronic obstructive pulmonary disease (COPD).

The number of monthly COPD deaths by gender and age was obtained from the Monthly Vital Statistics Reports of the Ministry of Health, Labour and Welfare. Data between January 1995 and December 2009 were used for analyses. The COPD mortality rate for each month was calculated separately for the two age groups: age <65 years and age ≥ 65 years. Changes in the COPD mortality rates after amendment were evaluated each month using the Poisson regression analysis to calculate risk ratios (RRs) and to compute 95% confidence intervals (95% CIs) adjusting for gender, age, trend and seasonal variations.

After amendments to the law, a statistically significant reduction in the COPD mortality rates were observed in January (RR 0.84; 95% CI 0.81-0.88), February (RR 0.85; 95% CI 0.81-0.89) and March (RR 0.92; 95% CI 0.88-0.96) among the population aged ≥ 65 years. However, in the population aged <65 years, statistically no significant changes in the COPD mortality rate were found in any month after the amendments were made.

A legal approach to improving influenza vaccine coverage for the elderly population would contribute to the risk reduction of COPD deaths during the influenza season.