In 2023, the Lives of 600 Million Are at Stake, Can the New Generation of Malaria Vaccines Turn the Tide?

Recently, the journal Nature Reviews Microbiology published a research report that thoroughly analyzed the development process of malaria vaccines and their effectiveness and challenges. Nearly half of the global population faces the threat of malaria, with pregnant women and young children being particularly vulnerable. Over time, women and children gradually develop partial resistance, providing possibilities for vaccine development. The clinical presentation of malaria is often misdiagnosed as non-specific influenza-like symptoms, leading to delayed treatment. The symptoms range from mild to severe complications, and the mortality rate for untreated cases remains high.

In 2022, malaria caused more than 600,000 deaths, and the mortality rate has not shown significant improvement since 2015. Five species of Plasmodium parasites can cause human malaria, with Plasmodium falciparum responsible for the most cases and deaths. The continued existence of malaria is partly attributed to parasite drug resistance and mosquito vector resistance to insecticides. Furthermore, climate factors such as temperature, humidity, and increased rainfall have exacerbated vector breeding, expanding the risk areas, particularly due to population movements driven by food and economic insecurity, which may increase the risk of malaria transmission.

The 2023 World Malaria Report states that R21 and RTS,S vaccines have become the first approved malaria vaccines, primarily targeting the circumsporozoite protein (CSP) of the parasite, with the potential to significantly reduce child mortality. RTS,S has shown a 36% reduction in clinical malaria in high to moderate transmission areas, while R21 has demonstrated a 75% (seasonal) or 68% (standard) reduction in clinical malaria in subsequent doses. However, the protective efficacy of these vaccines wanes over time, requiring annual booster doses, and their effectiveness may vary depending on transmission intensity and timing of administration. Additionally, the supply of saponin extracts used in the vaccine components is limited, and the current vaccines are mainly targeted at young children.

Pre-erythrocytic vaccines and blood-stage vaccines target different stages of the parasite, aiming to prevent infection and clinical symptoms. While some progress has been made in liver-stage vaccines, the development of blood-stage vaccines, particularly those targeting the complex variations of the PfEMP1 family, still faces significant challenges. The development of VAR2CSA as a leading candidate for pregnancy-specific malaria vaccines and the advancement of transmission-blocking vaccines provide new research directions for malaria control.

Although the R21 and RTS,S vaccines have achieved breakthroughs, their limitations indicate the need for continuous development of new strategies, including improving existing vaccines, developing vaccines for different age groups, and integrating genomics technology to strengthen public health responses, effectively monitor, prevent, and control infectious diseases.