Malaria: Developing Modern Vaccines for a Hard-to-Cure Disease

Malaria kills hundreds of thousands of people each year globally, with most of these being children. According to a report by the WHO, almost half of the world’s population was at risk of malaria in 2021, including infants, children under five years old, patients with HIV/AIDS, and pregnant women.

Disruptions caused by COVID have resulted in an additional 13 million malaria cases and 63,000 more deaths over the two peak years of the pandemic. Approximately 247 million people were infected by malaria in 2021, with about 619,000 fatalities.

Approximately 95% of global malaria cases and about 96% of fatalities occur on the continent of Africa, with four countries accounting for nearly half of all malaria deaths globally, namely Nigeria (31.3%), the Democratic Republic of the Congo (12.6%), Tanzania (4.1%), and Niger (3.9%).

A disease that is difficult to prevent and cure

Although malaria is curable, it is hard to prevent and treat the disease as a result of the high adaptability of the vector and parasites involved. Plasmodium, the malarial parasite, includes several species that cause the disease, with each having a highly complicated life cycle.

The deadliest of these species is Plasmodium falciparum, while Plasmodium vivax is the most prevalent. The mosquito vector Anopheles also has around 30 to 40 species under its name that can transmit the disease, each having different ecological and behavioral characteristics.

Worldwide, scientists have been working on the genomics of parasites and vectors to discover ways to fight the disease.

Alternative preventive methods include particular types of chemotherapies that involve giving a full treatment course to vulnerable populations. However, this only suppresses the stages of malaria to prevent serious organ failure.

All these treatments have one key weakness: the disease can return.

This article outlines the challenges associated with curing malaria and stresses the importance of modern vaccine development for the treatment of the disease.

Image Credit: B Medical Systems

Promising vaccines

Drugs can prevent malaria with varying rates of efficiency. Numerous factors contribute to this, such as the overuse of antimalarial drugs, incomplete or inadequate treatment of active infections, and, most significantly, the high level of metabolic and genetic adaptability of the parasites.

As a result, the best route to fight malaria would be the use of a vaccine that can achieve improved prevention and lessen the mortality of the disease.

Under development since the 1960s, malaria vaccines have encountered many obstacles: the malarial parasites generate highly complex antigens, making vaccine development very challenging. However, the introduction of mRNA technology and genome sequencing has enabled significant development.

Today, there are two vaccines for malaria. One of these is RTS,S, (MosquirixTM), which was approved a year ago by the WHO and is currently being utilized in pilot programs across high-risk areas.

The vaccine was first produced in 1987, but because of insufficient knowledge about the protein structures and the lack of available technological capabilities, the vaccine was only endorsed by the WHO for “broad use” in children in October 2021.

The vaccine is produced as a two-vial formulation: one of the vials contains the lyophilized antigen (RTS, S) which is required to be reconstituted with the second vial, which contains the Adjuvant System (AS01) in liquid form.

The lyophilized antigen is thermostable, while the liquid portion is temperature-sensitive and can become hydrolyzed, i.e., broken down via a chemical reaction with water.

As a result, MosquirixTM must be stored at a temperature between 2 °C and 8 °C. Failure of this could damage the antigen and/or adjuvant and decrease the vaccine’s safety or efficacy.

The second available vaccine is R21, or Matrix MTM, which is comprised of fusion proteins and the Matrix MTM adjuvant, which stimulates the recipient’s immune response to the vaccine.

However, this vaccine has not yet been approved by the WHO but has demonstrated an efficacy of approximately 77% in over 12 months of trials in Burkina Faso, a country where more than 4 million people died as a result of malaria in 2019.

The benefits of this vaccine compared to MosquirixTM include higher efficacy and a lower antigen dose required.

R21 is also a two-vial vaccine, composed of the R21 protein, which is extremely temperature sensitive and is required to be stored at -80 ⁰C, and the Matrix MTM adjuvant, which, in addition to needing to be stored at temperatures between 2 °C and 8 °C, is also photosensitive.

A key challenge facing the proper use of these vaccines is the inaccuracies in the logistics presently employed around them.

As various parts of the vaccines are extremely temperature-sensitive, they must be transported and reliably stored at low temperatures. This means that having the required cold chain to maintain these vaccines at their optimal conditions is critical.

Extremely critical packaging, transport, and distribution conditions

Long-term storage and delivery of vaccines are vital, especially as governments seek to vaccinate rural and remote communities. This requires cold chain infrastructure investments, workforce training, and, very importantly, last mile coordination

Luc Provost, CEO, B Medical Systems.

He continues: “It is challenging for pharmaceutical companies to create thermostable vaccines since biological molecules in aqueous solutions are inherently unstable.”  

“However, this creates a severe issue for areas with high ambient temperatures where maintaining a protective cold chain is challenging because of a lack of infrastructure. The lack of proper cold chain systems can lead to a reduction in the potency and therefore efficacy of the vaccines,”

Cold chain disruptions may be caused by several factors, including sudden blackouts triggered by an unreliable electricity infrastructure, the use of outdated or inadequately managed refrigerators and freezers, or poor compliance with cold chain procedures.

As a result, it is imperative to employ medical cold chain solutions whose parameters and effectiveness have the ability to be tracked and controlled, in addition to systems that have the ability to operate successfully in regions with unreliable power supplies for prolonged periods while retaining the necessary temperatures.

Provost highlights: “Temperature variations inside the freezers or transport boxes need to be monitored to prevent any risk as temperature variations could lead to the denaturation and spoilage of all biological products stored inside. That simply cannot happen. Ruining a stock of vaccines will not only cost a lot of money, but it could ultimately lead to deaths.”

He concludes: “In tropical countries, the difference in temperatures between the inside and the outside of a freezer can reach 120°C. It is therefore crucial to use cold chain solutions specifically designed for such extremes, and to equip them with the needed optional accessories such as independent power supplies, localization systems, and alarms.”

References 

  1. Global Malaria Programme (2021). World malaria report 2021. World Health Organization.  https://www.who.int/publications/i/item/9789240040496 

About B Medical Systems S.à r.l

B Medical Systems S.à r.l (formely Dometic/Electrolux) is a global manufacturer and distributor of medical cold chain solutions. Based in Hosingen, Luxembourg, the company was founded in 1979, when WHO approached the Swedish manufacturing giant Electrolux to provide a solution to safely store and transport vaccines around the world. Across the 3 major business portfolios of Medical Refrigeration, Blood Management Solutions, and Vaccine Cold Chain, the company currently offers 100+ models. B Medical Systems’ major products include Laboratory Refrigerators, Laboratory Freezers, Pharmacy Refrigerators, Ultra-Low Freezers, Plasma Freezers, Contact Shock Freezers, Vaccine Refrigerators (Ice-Lined Refrigerators and Solar Direct Drive Refrigerators), and Transport Boxes. All products have integrated 24/7 temperature monitoring capabilities that further ensure that these products offer the highest level of safety and reliability.


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Last updated: May 10, 2023 at 8:07 AM

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