Sociodemographic inequalities in COVID-19 booster vaccination in Peru: a GINI index decomposition analysis

ABSTRACT Background COVID-19 vaccine coverage, especially in booster doses, remains a significant issue in Peru. This study aimed to analyze the social determinants that affect vaccine coverage and evaluate sociodemographic inequalities in COVID-19 booster dose vaccination in Peru. Methods An ecological study was conducted with 196 provinces in Peru. GINI index decomposition analysis was performed to assess the inequality of immunization coverage in these provinces, considering sociodemographic characteristics as sources of inequality (sex, age group, educational level, residence area, and ethnic group). The Oaxaca-Blinder method was utilized to decompose the GINI index into Sk (composition effect), Gk (redistribution effect), Rk (differential effect), share value, and percentage change. Bootstrap method based on percentiles was employed to determine 95% confidence interval values for each GINI index and percentage change in the decomposition analysis. Results A total of 196 Peruvian provinces were evaluated. Among these, 59.74% had higher education, while 10.37% had no education or only elementary education. White or mestizo individuals accounted for 51.62% of the population. The GINI index decomposition analysis, six months after the start of the third and fourth dose vaccination campaign, revealed higher Sk values for the white or mestizo ethnic group (Sk= 6.46 vs Sk= 3.03), people living in rural (Sk= 6.63 vs Sk= 2.76) or urban areas (Sk= 5.88 vs Sk= 2.76), and those aged between 30 and 64 years (Sk= 6.84 vs Sk= 3.20). The highest Gk values were observed for the Aymara (Gk= 0.92 vs Gk= 0.92), Afro-Peruvian (Gk= 0.61 vs Gk= 0.61), and Quechua (Gk= 0.53 vs Gk= 0.53) ethnic groups, in contrast to the white or mestizo group (Gk= 0.34 vs Gk= 0.34). Furthermore, Rk exhibited high positive values for individuals with university or postgraduate education (Rk= 0.59 vs Rk= 0.44) and those living in urban areas (Rk= 0.34 vs Rk= 0.28). Conversely, individuals living in rural areas (Rk= -0.34 vs Rk= -0.28), those with elementary education (Rk= -0.46 vs. Rk= -0.36), and those with no education or only preschool education (Rk= -0.41 vs. Rk= -0.32) displayed high negative Rk values. Conclussion Sociodemographic inequalities exist in the coverage of third and fourth booster doses against COVID-19 in Peruvian provinces, particularly concerning geographic location, ethnicity, and educational level.