Influenza vaccination coverage in Chiburijima Island, Japan: Impact of diversification of vaccination place

Background To increase the influenza vaccination rate in Chiburijima Island, we diversified vaccination places from a single clinic to the seven town halls from all the districts. Methods We retrospectively analyzed influenza vaccination coverage, vaccinees' district of residence, and location of vaccination place, from prevaccination screening questionnaires between October 2007 and March 2018. Except for home‐visiting vaccination services, before 2011, influenza vaccination was provided only at a single clinic; after 2012, it was provided at the seven town halls in addition to the clinic. We calculated the vaccination rates among residents of Chiburijima Island, stratified by age groups and districts of residence. Results Estimated influenza vaccination rates for all ages increased from 38% in 2007 to 58% in 2017. There was a 14% increase in coverage in 2010 (the year following the 2009 H1N1 pandemic) and a slight increasing trend after 2012. The vaccination coverage of residents, particularly of people ≥65 years old and living >1 km from the former vaccination place, increased after diversification of the vaccination place. Conclusions Influenza vaccination rate in Chiburijima Island increased by 20% between 2007 and 2017, although the rate among the elderly Japanese people decreased by 4% based on the national data of routine immunization. Shortening the distance to vaccination places might improve the coverage as elderly people are often restricted due to transportation means. Sustained and multifaceted strategies are necessary for better immunization coverage.