The impacts of priority settings at the start of COVID-19 mass vaccination on subsequent vaccine uptake in Japan: One-year prospective cohort study.

Abstract

Distributing COVID-19 vaccines to the people was an important task for the governments of each country. Due to various limitations, priority settings for vaccination were determined at the launch of mass vaccination. However, trends between vaccine intention and uptake, and reasons for getting vaccinated, or not getting vaccinated among these groups were understudied, undermining verification of the legitimacy of the selection of priority. (1) To illustrate a trend from prior COVID-19 vaccine intention, when the vaccine was not available, to the actual uptake within one year when all residents have access to vaccine; (2) To illustrate a change of reason for getting vaccinated or not getting vaccinated; (3) To examine whether priority settings predicted subsequent vaccination uptake. Prospective cohort online self-administered surveys were conducted in Japan at three timepoints: February 2021, September-October 2021, and February 2022. In total, 13,555 participants (53.1 years old on average) provided valid responses, with 52.1% follow-up rate. Based on the information obtained in February 2021, healthcare workers (n = 831), people aged 65 years or older (n =4,048), and those aged 18-64 years with underlying medical conditions (n = 1,659) were identified as three types of priority group. The remainder were treated as a non-priority group (n = 7,017). Modified Poisson regression analysis with a robust error estimated risk ratio for COVID-19 vaccine uptake after adjusting for socioeconomic background, health-seeking behavior, attitude toward vaccines, and COVID-19 infection history. In February 2021, 38.2% of the total respondents said they had intention to receive the vaccination. In February 2022, 11.6% completed the third dose and 78.1% completed the second dose vaccination. Prior vaccine intention and subsequent vaccine coverage rates were higher in the priority groups. Protection of themselves and their families from potential infection was the most frequent reason for getting vaccinated, while concern about side effects was the most frequent reason to be hesitant across the groups. Risk ratios for receiving, reserved, or intended for vaccination in February 2022 were 1.05 (95% Confidence Interval: 1.03, 1.07) for the healthcare worker group, 1.02 (95% Confidence Interval: 1.005, 1.03) for the elderly group, and 1.01 (95% Confidence Interval: 0.999, 1.03) for the pre-exiting conditions group compared to the non-priority group. Prior intention for vaccination and confidence in vaccines were strong predictors for vaccine uptake. The priority settings at the start of the COVID-19 vaccination program had a significant impact on the vaccine coverage one year later. The vaccination priority group achieved higher vaccination coverage in February 2022. There was a room to improve among the non-priority group. This study's findings are essential for policymakers in Japan and other countries to develop effective vaccination strategies for future pandemics.