Findings from the POPVAC studies highlight determinants of vaccine response in Uganda
In the November 2024 issue of The Lancet Global Health journal, four insightful articles from the groundbreaking POPVAC (Population Differences in Vaccine response) clinical trials are out now. Funded by the UKRI / MRC, the POPVAC trials ran between 2018 and 2022 and explored how environmental factors as well as chronic infections shape immune responses across adolescent schoolchildren living in distinct urban-rural areas in Uganda. The principal investigator for the project was Professor Alison Elliott and other members of the POPVAC research team included Dr Gyaviira Nkurunungi, Dr Ludoviko Zirimenya, Ms Agnes Natukunda, Ms Jacent Nassuuna and Professor Emily Webb.
POPVAC Team in the field
Understanding what drives differences in immune responses to vaccines across different populations is at the core of HypoVax Global’s overall objectives so the findings from these trials are particularly relevant to our goals and activities. One of the overall major findings of the POPVAC trials was that responses to several vaccines differ markedly between urban and rural settings within Uganda. When it comes to the individual trials, POPVAC Trial A examined whether treating adolescents for the waterborne infectious disease schistosomiasis would improve vaccine responses. This trial was conducted in the highly schistosomiasis endemic Koome Islands of Mukono District in the Central Region of Uganda. When it came to the findings, POPVAC Trial A observed that treatment for schistosomiasis with praziquantel improved BCG vaccine responses although the effect on other vaccines was less pronounced. Based on these findings, more work is needed to investigate whether sustained control of helminth infections could be a measure to implement to improve vaccine efficacy.
POPVAC Trial B was conducted in the rural Jinja district of Eastern Uganda where malaria is heavily endemic. The trial investigated whether giving adolescents intermittent preventive treatment (IPT) for malaria using dihydroartemisinn-piperaqyine would lead to better immune responses to vaccines. Although IPT successfully reduced the prevalence of malaria in the trial, it did not significantly improve vaccine responses. The third trial, POPVAC Trial C, explored whether BCG revaccination among urban adolescents living in the Entebbe Municipality improved immune responses to unrelated vaccines that were given as part of the trial. POPVAC Trial C found that BCG revaccination did not enhance immune responses to other vaccines. Taken together, these studies illustrate the complexity and multiple factors that underly immune responses to vaccines in resource-limited settings in the Global South.
Dr Gyaviira Nkurunungi working on POPVAC samples in the lab
What is next?
The results of the POPVAC trials have already paved the way for a series of follow-up investigations aimed at exploring how biological and social factors influence immunisation outcomes and the need for the development of tailored vaccine approaches for diverse communities and populations.
One such study is the Vaccines for Vulnerable People in Africa (VAnguard) study which is a UK NIHR Global Health Research funded initiative which examines the biological and social factors that impact vaccine efficacy in Uganda and Kenya. VAnguard aims to understand how these factors interact and could potentially hinder the impact of vaccines in vulnerable African communities. The overall goal of the VAnguard project is to develop integrated strategies to optimise the benefits of vaccines and drive health equity.
The POPVAC Trial articles can be downloaded from The Lancet Global Health website where they are all available via open access. More information about the trials can be found via the MRC/UVRI LSHTM Uganda Research Unit website.
Congratulations to the POPVAC research team for their hard work!