Rapid Rollout and Initial Uptake of a Booster COVID-19 Vaccine Among Israel Defense Forces Soldiers.

The surge of breakthrough COVID-19 among fully vaccinated individuals has raised the prospects of booster dose administration. In Israel, concerns of waning immunity and dominance of the B.1.617.2 (delta) variant resulted in approval of a third-dose (booster) vaccination for the entire eligible population starting on August 29, 2021. This study aims to evaluate vaccine uptake for booster doses among a population of previously vaccinated individuals during a rapid rollout and to analyze socio-demographic characteristics associated with vaccine uptake. A cross-sectional study among Israel Defense Forces soldiers with high access to booster doses of BNT162b2. Subjects eligible for booster doses were voluntarily vaccinated at three vaccine sites constructed within soldiers' bases. We analyzed associations between subjects' socio-demographic characteristics and booster vaccine uptake at the culmination of vaccine rollout using logistic regression models. 1157 soldiers from an IDF brigade were eligible for third dose vaccination (received second dose > 5-months before rollout), with 978 (84.5%) receiving a third, booster dose during the study's timeframe. Subjects' median age was 20.5 (IQR 19.7-21.5) and 791 (68.4%) were male. Notable socio-demographic characteristics associated with increased vaccine uptake in a multivariable model included increased age (OR 1.16, 95% CI 1.02-1.31), high socio-economic status (OR 2.12, 95% CI 1.25-3.59) and female sex (OR 1.87, 95% CI 1.26-2.74). Below-average cognitive function score was associated with decreased vaccine uptake (OR 0.61, 95% CI 0.39-0.95). This study demonstrates that real-world vaccine hesitancy remains a major obstacle, even among a population previously acceptant to COVID-19 vaccines. Decreased uptake for vaccines may be associated with socio-demographic variables in-spite of high-access vaccine rollouts. Reasons for vaccine hesitancy among previously vaccinated individuals, along with the benefits of population-wide booster administration should be further investigated.