Tuesday, January 18

World’s First Mass Launch of Malaria Vaccine Could Prevent Thousands of Children from Dying

The world’s first mass vaccination program against malaria, announced this week, is established to prevent millions of children from contracting malaria and thousands from dying from this debilitating disease.

The World Health Organization (WHO) has recommended Widespread use of the RTS vaccine, S / AS01 (Mosquirix) in young children most at risk of malaria in Africa.

Malaria is a big problem

Mosquitoes transmit the parasite Plasmodium falciparum from person to person when they bite. So until now, our fight against malaria has consisted of using mosquito nets to prevent bites and spraying insecticides to kill mosquitoes. Then there are the drugs to prevent or treat malaria infection.

However, the parasite has developed resistance to antimalarial drugs and mosquitoes have developed resistance to insecticides. However, existing control measures have led to a significant decrease in the number of malaria deaths since 2000.

In recent years, however, progress has stalled. In 2019, malaria infection Resulted in 409,000 deaths worldwide, mainly in children under the age of five, and 229 million new cases of malaria.

African child under mosquito net
Mosquito nets only go so far. Therefore, other measures are needed to control malaria.
Image: Shutterstock

Therefore, we need additional tools, such as an effective vaccine against malaria, if we want to control the disease globally.

The WHO recommendation to implement the Mosquirix vaccine in children at high risk of infection by P. falciparum, which is widespread in Africa, is an important step towards controlling the deadliest human malaria parasites.

What did the WHO recommend?

The WHO recommended four doses of the vaccine in children from the age of five months.

This recommendation follows the recent results of a pilot program in Ghana, Kenya and Malawi, which means more than 800,000 children have been vaccinated since 2019.

The program demonstrated that delivery of the vaccine is feasible and cost-effective in high-risk areas. The number of children also increased (to more than 90%) who have access to at least one intervention to prevent malaria.

The vaccine has a good safety profile and reduces cases of clinical and severe malaria, which can be fatal.

What do we know about the vaccine?

Mosquirix is ​​a “subunit” vaccine. This means that it only contains a small part of the malaria parasite, which is produced as a synthetic protein.

This protein is combined with an “adjuvant”, a molecule designed to stimulate a strong immune response.

The vaccine works primarily by stimulating the body to produce antibodies against the parasite, neutralizing it and preventing it from entering liver cells. These are the first cells that the parasite invades when it enters the body.

The vaccine also works by helping to assemble a inflammatory answer, when a different part of the immune system responds.

The vaccine is not perfect

The level of protection provided by the vaccine is not ideal. Protection it varies with the age of the child when vaccinated, with less protection for young babies compared to older children. In older children (5 to 17 months of age), this averaged about 36% protection against the development of clinical malaria over a four-year period.

Protective immunity also decreases rapidly over time. This means that regular booster doses will be required. Alternative vaccination schedules are also being evaluated.

However, the vaccine can still make a significant contribution to malaria control when used in high-risk areas for malaria and with other control measures.

A modeling study estimated that in sub-Saharan Africa, Mosquirix could prevent up to 5.2 million cases of malaria and 27,000 deaths of young children each year.

Why has it taken so long to get here?

Developing a vaccine against malaria is challenging. Technically, it is difficult to develop a vaccine against a parasite that lives in two hosts (mosquitoes and humans).

There has also been limited interest from pharmaceutical companies in developing a malaria vaccine.

Although travelers would benefit from a vaccine when traveling to affected countries, the people most in need of a malaria vaccine live in some of the poorest countries in the world. Therefore, there are few financial incentives to develop a vaccine.

Mosquirix is ​​the result of more than 30 years of research and was created through a partnership between GlaxoSmithKline (GSK) and the Walter Reed Army Institute of Research in the USA.

This period of time is not long considering that both the antigen design and the adjuvant system were novel.

The Bill and Melinda Gates Foundation and GSK supported further development, including evaluation of the vaccine in clinical trials. For three decades, they invested around US $ 700 million to develop the vaccine.

Whats Next?

This current version of Mosquirix is ​​not expected to be the latest.

Preliminary results for a new modified vaccine, called R21, they are encouraging.

Other malaria vaccines in development include whole parasite vaccines. These use the all the malaria parasite who has been murdered or altered so it cannot cause a malaria infection, but it can still stimulate an immune response.

Passive vaccines they are also being investigated. These involve injecting long-lasting antibodies to prevent malaria infection.

A whole new set of challenges

Meanwhile, the WHO recommendation presents a new set of challenges.

Countries affected by malaria must decide whether to include Mosquirix as part of their national malaria control strategy.

Critical funding decisions from the global public health community will be needed to enable wide deployment of the vaccine among the children who will benefit the most from it.

Manufacturing capacity of tens of millions of doses each year, global vaccine supply chains, and distribution infrastructure in malaria-affected countries will also be needed.

Finally, each country will need to maximize the uptake of the vaccine and ensure completion of the four-dose immunization program to obtain the full benefit of the vaccine.

Correction: This article originally said that the Bill & Melinda Gates Foundation and GSK invested about $ 700 billion to support vaccine development, instead of $ 700 million.The conversation

Danielle stanisic, Research Associate Leader, Glycomics Institute, Griffith University and Michael good, Professor and Researcher Fellow at NHMRC, Institute for Glycomics, Griffith University

This article is republished from The conversation under a Creative Commons license. Read the Original article.


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