Developing a vaccine against HIV has long been difficult due to the virus’s ability to rapidly mutate and conceal critical components from the immune system. However, promising new findings from two phase 1 clinical trials suggest a breakthrough may be within reach.
The international research, led by IAVI and Scripps Research, involved nearly 80 participants from North America and Africa, including Kenyan scientists, and was published in Science on May 15, 2025. One trial used a stepwise vaccination approach – first giving a priming dose, then a distinct booster shot – to guide the immune system in developing broadly neutralising antibodies (bnAbs). These rare antibodies are capable of targeting multiple HIV variants, even as the virus mutates.
In one trial, the heterologous boosting method successfully progressed the immune response in participants. The second trial confirmed that the priming dose alone could activate the desired immune cells in African volunteers, highlighting the strategy’s viability in high-burden regions like Kenya, where an estimated 1.4 million people live with HIV.
Both trials employed mRNA-based vaccines, a technology that offers rapid production and strong immune responses – similar to what was used in COVID-19 vaccines.
Lead scientist Prof. William Schief of Scripps and IAVI emphasized the importance of having proven the approach works in African populations. Kenyan institutions involved included KAVI–Institute of Clinical Research (University of Nairobi) and the Kemri Wellcome Trust.
The trials mark a major step in a technique called germline targeting, which aims to prime rare B cells to eventually produce bnAbs. Although the trials didn’t yet generate bnAbs, they successfully demonstrated the feasibility of steering the immune system toward this goal.
Researchers and partners hailed the results as a testament to global scientific collaboration, with hopes this work will eventually lead to a viable HIV vaccine capable of transforming global public health.
