Background and Objectives: As the COVID-19 pandemic prolongs, the threat of twindemic with influenza and COVID-19 remains. Therefore, this study Aims to evaluate the effect of improving the influenza vaccination coverage rates of free vaccination expansion program before and during the COVID-19 pandemic. Methods: The present study used the 2020~2021 Korea Community Health Survey (KCHS) data from Kyungpook province in Korea, which includes 23 cities/counties. We analyzed annual influenza vaccination rate, and the 2020 KCHS and 2021 KCHS Results meant the influenza vaccination rates for the 2019-2020 season and the 2020-2021 season, respectively, considering the KCHS survey period (mid-August to mid-October) and adult influenza vaccination period (mid-October or later). During the 2020~2021 season, unlike other regions, one city (Andong) of Kyungpook province introduced free vaccination program for all citizens. Results: The adult influenza vaccination coverage rate of 2020 and 2021 KCHS increased by only 1.8%p (52.9% in 2020, 54.7% in 2021) in Kyungpook, but increased by 9.4%p (55.9% in 2020, 65.3% in 2021) in Andong. As a Results of comparison by age group in 10-year intervals, vaccination coverage rates for those in their 60s and 70s or older, who were not subject to vaccination expansion program, showed no difference or slightly decreased in both regions between the 2020 and 2021 KCHS. However, the vaccination coverage rate increased respectively by 19.0%p, 15.0%p, and 21.6%p for those in their 30s, 40s, and 50s in Andong. On the other hand, in the 20s, the rate of increase was low in both regions. Conclusions: The expansion of the free influenza vaccine program was effective in improving the vaccination coverage rate among adults in their 30~50s, excluding those in their 20s. The temporary expansion of free vaccination programs will be efficient in preventing the twindemic between influenza, and COVID-19 or other emerging infectious diseases.