Malaria Vaccine

Let’s start with some facts on Malaria from the World Health Organization.

  • Malaria is a disease which can be transmitted to people of all ages. It is caused by parasites of the species plasmodium that are spread from person to person through the bites of infected mosquitoes. If not treated promptly with effective medicines, malaria can often be fatal.
  • About 3.3 billion people – half of the world’s population – are at risk of malaria. Every year, this leads to about 250 million malaria cases and nearly one million deaths. People living in the poorest countries are the most vulnerable.
  • One in five (20%) of all childhood deaths in Africa are due to malaria. It is estimated that an African child has on average between 1.6 and 5.4 episodes of malaria fever each year. Every 30 seconds a child dies from malaria in Africa.
  • Early diagnosis and prompt treatment are two basic elements of malaria control. Early and effective treatment of malaria can shorten the duration of the infection and prevent further complications including the great majority of deaths. Access to disease management should be seen not only as a component of malaria control but a fundamental right of all populations at risk.
  • Inappropriate use of antimalarial drugs in the past century contributed to widespread resistance in the malaria parasite to drugs such as chloroquine, leading to rising rates of sickness and death. Over the past decade, a new group of antimalarials – known as artemisinin-based combination therapies – has brought new hope in the fight against malaria.
  • The main objective of malaria vector control is to significantly reduce the rate and number of cases of both parasite infection and clinical malaria. This is achieved by controlling the malaria-bearing mosquito and thereby reducing or interrupting transmission.
  • Long-lasting insecticidal nets can be used to provide protection to risk groups, especially young children and pregnant women in high transmission areas. This provides personal protection. The nets can also protect communities when coverage is high enough (more than 80% of people in a target community sleeping inside them). The nets are effective for a number of years (3 to 5 years, depending on models and conditions of use).
  • Indoor residual spraying is the most effective means of rapidly reducing mosquito density. Its full potential is obtained when at least 80 % of premises with malaria vectors are sprayed. Indoor spraying is effective for 3 to 6 months, depending on the insecticide used and the type of surface on which it is sprayed. (DDT is effective for longer periods, up to 12 months in some cases).
  • Pregnant women are at high risk not only of dying from the complications of severe malaria, but also spontaneous abortion, premature delivery or stillbirth. Malaria is also a cause of severe maternal anaemia and is responsible for about one third of preventable low birth weight babies. It contributes to the deaths of an estimated 10 000 pregnant women and up to 200 000 infants each year in Africa alone.
  • Malaria causes an average loss of 1.3% of annual economic growth in countries with intense transmission. It traps families and communities in a downward spiral of poverty, disproportionately affecting marginalized and poor people who cannot afford treatment or who have limited access to health care. Malaria has lifelong effects through increased poverty and impaired learning. It cuts attendance at schools and workplaces. However, it is preventable and curable.

World Malaria Map from the US CDC

There is some good news on the Malaria front:

Malaria is the third-deadliest disease in the world, behind AIDS and tuberculosis, according to BusinessWeek. About 780,000 deaths were caused by malaria in 2009, according to the WHO report. That’s a drop from the 985,000 total deaths in 2000

That’s a big decrease, but it’s still 780,000 deaths a year from this deadly disease. A paper just published in the New England Journal of Medicine presents an upcoming weapon in the fight against malaria—a vaccine.

It’s been a long time coming, and indeed we are still not there yet, but it is becoming increasingly clear that we really do have the first effective vaccine against a parasitic disease in humans. If there are no unforeseen disasters, the RTS,S/AS01 Plasmodium falciparum malaria vaccine should become available in just over 3 years. The World Health Organization (WHO) has already taken the unusual step of indicating that it could recommend this first malaria vaccine for use in some African countries as early as 2015, depending on the full phase 3 trial results that will become available in 2014.1 The vaccine has been developed by a public–private partnership between GlaxoSmithKline and the Program for Appropriate Technology in Health (PATH) Malaria Vaccine Initiative, supported by the Bill and Melinda Gates Foundation, primarily for use in infants and young children in sub-Saharan Africa. RTS,S/AS01 is a hybrid construct of the hepatitis B surface antigen fused with a recombinant antigen derived from part of the circumsporozoite protein. This is the protein coat of the sporozoite, the parasite stage that is inoculated by the feeding anopheline mosquito, which then invades liver cells and multiplies there before entering the bloodstream. Keys to the success of the vaccine are the immunogenic polymeric nature of RTS,S particles and the proprietary adjuvant AS01.

As in any vaccine, or indeed, any effective treatment, there is the potential for unwanted side effects.

Trials often throw up unexpected findings. In this trial, there were significantly more cases of meningitis among children receiving the RTS,S/AS01 vaccine than among those receiving the comparator vaccines. There seems to be no plausible explanation for this, and it may well turn out to be a chance finding, but it cannot be ignored. On the other hand, the increased risk of febrile reactions or seizures among RTS,S/AS01 recipients may be real, reflecting the reactogenicity of this highly immunogenic vaccine. Such questions highlight the importance of phase 4 studies of both safety and effectiveness with active surveillance if this vaccine is deployed.

The probability and severity of these side effects must be weighed against the potential for harm from contracting the disease and the effectiveness and side effects from current treatment options. The most common antimalarial drugs available today are:

A newer drug used in some parts of the world is Artesunate. It is showing great promise, but it too has side effects, and for various reasons is not available worldwide.

None of these are without serious side effects and in many parts of the world, resistance to chloroquine has rendered the drug ineffective. The mode of action of these medications renders the same drug ineffective as a treatment if it is used as a prophylaxis.

The prevention techniques described above are still the most effective means of controlling malaria. A vaccine will not wipe out the disease, but it does add another tool to the arsenal.

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2 Responses to Malaria Vaccine

  1. Pingback: Breakthrough in Oxford malaria research | Innovation Toronto

  2. Pingback: Another Malaria Vaccine | PEI Curmudgeon's Blog

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