Vaccine spillover effects in Africa: A cross-national study of vaccine spillover and confidence in Kenya, Nigeria, and South Africa

• Published in: Vaccine 2025-01, Vol.43 (Pt 2), p.126528, Article 126528
• Main Authors: Lockman, Alee, Callaghan, Timothy, Blackburn, Christine Crudo, Colwell, Brian
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Africa; Confidence; COVID-19; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 vaccines; COVID-19 Vaccines - administration & dosage; Cross-Sectional Studies; False information; Female; Health Knowledge, Attitudes, Practice; Humans; Immunization; Influence; Kenya; Male; Middle Aged; Multivariate analysis; Nations; Nigeria; Pandemics; Pharmaceutical industry; Qualitative research; Regression analysis; SARS-CoV-2 - immunology; South Africa; Surveys and Questionnaires; Trust; Vaccination - psychology; Vaccination - statistics & numerical data; Vaccination Hesitancy - psychology; Vaccination Hesitancy - statistics & numerical data; Vaccine hesitancy; Vaccine spillover; Vaccines; Variables; Young Adult
• ISSN: 0264-410X; 1873-2518; 1873-2518
• DOI: 10.1016/j.vaccine.2024.126528

Vaccine hesitancy and a distrust of the COVID-19 vaccine is widespread in many African nations, stemming from historic medical abuses and low confidence in governments. While studies have examined drivers of vaccine hesitancy in Africa, little is known about vaccine spillover effects: how prior experiences with vaccines influence individuals' confidence in vaccines and future vaccination behaviors. In a large online survey conducted across three African countries (Kenya, N = 1545; Nigeria, N = 1557; South Africa, N = 1588), we examined five measures of vaccine spillover: how experiences with the COVID-19 vaccination process influenced respondents' confidence in the safety, efficacy, and importance of all vaccines approved for use in their country, and the likelihood of vaccinating themselves or their children in the future. Multivariate binary logistic regression analyses were conducted to determine factors associated with each of the five outcome measures. Large numbers of individuals in all three countries experienced positive vaccine spillover: becoming more likely to vaccinate in the future and experiencing greater confidence in vaccines, due to their prior experiences with the COVID-19 vaccination process. The highest positive spillover effects were observed in Kenya, with 71 % reporting a greater likelihood of vaccinating themselves in the future, compared to just 60.1 % of Nigerian respondents and 51.7 % of South African respondents. Multivariate models provide evidence that demographic correlates of positive vaccine spillover vary across nations; however, prior vaccination, misinformation endorsement, and confidence in government both consistently predict spillover in all three nations. These findings suggest that while drivers of vaccine spillover are country specific, strategies to address COVID-19 misinformation and to strengthen individuals' trust in government may help facilitate greater vaccine uptake in the future.