THE DISEASE - MALARIA

WHAT IS MALARIA?

Malaria is a life-threatening disease caused by parasites transmitted through the bite of infected mosquitoes.

Malaria is transmitted through the bite of female Anopheles mosquitoes carrying Plasmodium parasites. Malaria is not directly transmitted from person to person.

What are the symptoms of malaria?

Symptoms include fever, chills, sweating, headache, muscle aches, nausea, and vomiting.

How long does it take for malaria symptoms to appear after infection?

Malaria symptoms typically appear between 7 to 30 days after the bite of an infected mosquito, depending on the type of parasite.

Can malaria be fatal?

Yes, malaria can be fatal if not promptly diagnosed and treated, particularly in young children, pregnant women, and individuals with weakened immune systems.

Who has a higher risk of Malaria infection?

Malaria disproportionately affects children under the age of 5 and pregnant women. In 2022, children under 5 accounted for approximately 80% of all malaria deaths in Africa.

Pregnant women are particularly vulnerable to malaria and should take extra precautions to avoid mosquito bites and follow antimalarial medication guidelines under medical supervision.

How does one diagnose malaria?

Malaria diagnosis is typically confirmed through microscopic examination of blood samples to detect the presence of malaria parasites.

Where is malaria most commonly found?

Malaria is most commonly found in tropical and subtropical regions, South Asia, and parts of Central and South America. In 2022, the majority of malaria cases and deaths are concentrated in sub-Saharan Africa, which accounted for about 95% of malaria cases and 96% of malaria deaths. Nigeria, the Democratic Republic of the Congo, Uganda, and Mozambique are among the countries with the highest burden.

How can malaria be prevented?

Prevention methods include using insect repellent, sleeping under insecticide-treated bed nets, taking antimalarial medication if traveling to affected areas, and eliminating mosquito breeding sites.

What are the available treatments for malaria?

Antimalarial drugs such as chloroquine, artemisinin-based combination therapies (ACTs), and other medications are used for treating malaria.

Antimalarial drugs resistance occurs when malaria parasites evolve and become resistant to the effects of antimalarial drugs, making treatment less effective.

Why is a vaccine needed?

Because a century of work on control and eradication has failed to eliminate this scourge.

The Fight against malaria

Malaria can lead to various complications, including anemia, neurological damage, and organ failure, which may have long-term effects on health if not treated promptly.

CURRENT VACCINE STRATEGIES

Multiple vaccines strategies can offer progress in the fight against malaria, particularly in high-burden regions, however these vaccines require several clinic visits and modest efficacy.

Continued research and development are essential to improve efficacy, extend protection duration, and develop new vaccines targeting different malaria strains.

Anti-infection

Interrupting infection during the mosquito-to-skin-to-liver (“pre-erythrocytic”, PE) stages would prevent progression to the erythrocytic stage, where both disease and transmission occur (Draper et al. 2018; Kurtovic et al. 2021).

RAS: “Sterile protection” has been achieved in animals and humans using repeated immunizations with whole-organism (WO) radiation-attenuated sporozoites (RAS), but this regimen is very costly because it requires high doses of sporozoites (SPZ) from mosquitoes (Patel et al. 2017; Jongo et al. 2021; 2023).

GAP: Genetically-attenuated parasites (GAP) that arrest in the liver have been generated by deleting genes critical for liver-stage development (Vaughan et al. 2018; Kublin et al. 2017; Butler et al. 2011). Newer GAPs progress further into the liver stage, where they provide improved protection at lower doses (Goswami et al. 2020; Goswami, Minkah, and Kappe 2019).

CPS: Likewise, immunization with wild-type (WT) WO SPZ combined with chemoprophylaxis (CPS) can induce high levels of protection with smaller doses (Mwakingwe-Omari et al. 2021). In these WO approaches, primed T cells from the spleen are drawn to the liver, where antigen presentation is essential to generate protective liver-resident CD8+ T-cell memory responses (Krzych et al. 2012).

Anti-disease

Developing an "anti-disease" vaccine specifically targeting the blood stage of the parasite requires a deep understanding of the parasite's biology, the host immune response, and the complex interactions between the parasite and the host. Antigen targeting the merozoite invasion or the blood stages antigens are among the different vaccines approaches.

Transmission blocking

A transmission-blocking malaria vaccine targets the sexual stages of the parasite, preventing its development in the mosquito vector after it feeds on a vaccinated individual.

This type of vaccine aims to halt the spread of malaria by interrupting the life cycle of the parasite, thus reducing transmission within the population. It induces an immune response that inhibits parasite development in the mosquito.

As of 2024, there are two notable Malaria vaccines that have been recommended by the WHO for use, but those lack sterile protection:

RTS,S/AS01 (Mosquirix TM)

Manufacturer: GlaxoSmithKline (GSK).
Approval: Approved by the World Health Organization (WHO) in October 2021 for broader use.
Target Population: Designed for children aged 6 weeks to 17 months. Efficacy: Demonstrated to reduce malaria cases by about 39% and severe malaria by 29% over four years of follow-up in young children.
Implementation: It has been rolled out in pilot programs in several African countries including Ghana, Kenya, and Malawi. The WHO recommended its broader use in 2021 after observing its effectiveness and safety in these pilots.

R21/Matrix-M TM

Manufacturer: Developed by the University of Oxford, with Serum Institute of India as the manufacturing partner.
Approval: Approved for use in Ghana and Nigeria as of April 2023. Target Population: Primarily aimed at children aged 5 to 36 months.
Efficacy: Preliminary studies suggest it has an efficacy of around 77% over one year, which is notably higher than RTS,S.
Implementation: The vaccine has received regulatory approval in some African countries and is expected to play a significant role in malaria prevention efforts.

For more information on Malaria

WHO - Malaria

CDC - Malaria