Highlights from the WHO’s 2024 World Malaria Report

Author(s):  Dr Sherilyn Houle

On December 11, 2024, the World Health Organization’s 2024 World Malaria Report was released.¹ Here, we will discuss highlights related to recent changes in the epidemiology of malaria worldwide, vaccination for those living in areas at moderate or high risk of malaria, and what impact these vaccination programs may have on malaria risk among travellers.

Malaria Epidemiology

In 2023, 83 countries were endemic for malaria.¹ Cases overall have increased from 2020-2023, with four countries reporting increases exceeding 1 million cases over this period: Ethiopia (+4.5 million), Madagascar (+2.7 million), Pakistan (+1.6 million), and Nigeria (+1.4 million). Readers are encouraged to view Figure 2.1 on page 7 of this report, which illustrates graphically and proportionally the number of cases by country in 2023 and highlights differences in magnitude across WHO regions. For example, Brazil, the leading nation for case counts in the Region of the Americas, had 1 case per 13 cases in India (the leading nation in the South-East Asia Region) and 1 per 418 in Nigeria (the leading nation in the African Region).

While cases overall have increased from 2020-2023, counts year-over-year from 2022 to 2023 in the Americas declined by 65.4% (where Belize was also certified malaria-free in 2023), and in the South-East Asia Region cases declined in Bangladesh, India, Indonesia, and Nepal.¹

Malaria transmission, detection, and impact over time and geographically is affected by a complex interplay of factors including Plasmodium species distribution, vector control efforts, drug resistance, access to diagnostics, and climate change, among others.² As this report demonstrates, travel health clinicians must account for changing epidemiology when assessing a traveller’s risk of malaria and determining appropriate prophylactic measures.

Vaccination Programs

Two malaria vaccines have been marketed, recommended by the WHO for programmatic use “for the prevention of P. falciparum malaria in children living in malaria endemic areas, prioritizing areas of moderate and high transmission.”³ As of December 2024, 17 countries in Africa offer malaria vaccine as part of routine childhood immunization programs, with over 12.5 million doses delivered and additional countries expected to introduce similar programs.³

Both vaccines are pre-erythrocytic vaccines that prevent the invasion of liver cells and clear infected liver cells, thus protecting against subsequent human blood stages in the parasite life cycle.⁴ While some benefit on overall transmission via herd immunity can be anticipated if there are fewer infected humans, efforts to develop transmission-blocking vaccines (TBVs) are expected to have additional benefit on reducing the spread of malaria by blocking infection transmission from humans to mosquitoes.⁴ However, as TBVs do not protect the recipient from malaria, they are not of benefit to travellers and may instead complement mass immunization efforts in endemic regions along with the existing pre-erythrocytic vaccines.

The Bottom Line

Mosquito bite prevention and chemoprophylaxis for travellers at risk of malaria will continue to be the mainstay of malaria prevention efforts in travel clinics. Clinicians are encouraged to keep apprised of malaria epidemiology and drug sensitivities which can change significantly over time.

References:

1. World Health Organization. World Malaria Report 2024. https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2024.
2. Obeagu EI, Obeagu GU. Emerging public health strategies in malaria control: innovations and implications. Ann Med Surg (Lond) 2024;86(11):6576-6584. doi: 10.1097/MS9.0000000000002578.
3. World Health Organization. Malaria vaccines (RTS,S and R21). https://www.who.int/news-room/questions-and-answers/item/q-a-on-rts-s-malaria-vaccine.
4. El-Moamly AA, El-Sweify MA. Malaria vaccines: the 60-year journey of hope and final success - lessons learned and future prospects. Trop Med Health 2023;51:29. doi: 10.1186/s41182-023-00516-w.

References

[1].  World Malaria Report 2024.  World Health Organization [Link]
[2].  Emerging public health strategies in malaria control: innovations and implications.  Obeagu EI, Obeagu GU ‐ Ann Med Surg (Lond) 2024;86(11):6576-6584 [Link]
[3].  Malaria vaccines (RTS,S and R21).  World Health Organization [Link]
[4].  Malaria vaccines: the 60-year journey of hope and final success - lessons learned and future prospects.  El-Moamly AA, El-Sweify MA ‐ Trop Med Health 2023;51:29 [Link]