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Vaccine for Malaria

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A malaria vaccine is employed to prevent malaria. The only approved vaccine is RTS, S marketed under the name mosquirix.

Written by

Dr. Shuchi Jain

Medically reviewed by

Dr. Kaushal Bhavsar

Published At November 25, 2022
Reviewed AtNovember 25, 2022

Introduction:

The name malaria comes from an Italian word that means bad air. Before the development of germ theory, it was assumed that malaria was transmitted from contaminated air (or miasmas). But later on, it was discovered that mosquitoes (female Anopheles) were responsible for the transmission of malaria. Malaria is caused by the plasmodium species (parasites). Species of parasites that cause malaria in humans are - Plasmodium falciparum, vivax, ovale, malariae, and knowlelsi. Plasmodium falciparum is considered the most dangerous strain.

A malaria vaccine is advised for children who live in areas where malaria cases are frequently reported. The distribution of preventive drugs and insecticide-treated bed nets is another measure to get rid of malaria.

What Is Malaria?

Malaria is a parasitic disease. The bite of infected anopheles mosquitoes results in the spread of the disease to humans. The highest cases have been documented in tropical and subtropical countries. Malaria continues to plague humans. Each year, approximately two hundred ninety million people get infected, and more than four lakh people die of the disease. People suffering from malaria fell sick with high fever and chills.

What Are the Symptoms of Malaria?

Symptoms of malaria begin to come up within a few weeks.

The symptoms include:

  • A sense of discomfort.

  • Muscle, joint, and abdominal pain.

  • Fever.

  • Chills.

  • Headache.

  • Nausea, vomiting, and diarrhea.

  • Rapid breathing and elevated heart rate.

A classical feature of malaria is - an attack that starts with shivering and chills, followed by high fever, sweating and returning to normal body temperature. Before we understand how vaccines prevent malaria, let us first go through the parasite life cycle.

The Transmission Cycle of the Female Anopheles Mosquito Is as Follows -

The Pre-erythrocytic Stage:

  • Uninfected Mosquitoes: An uninfected mosquito can become infected by feeding on the blood of a person who has malaria.
  • Parasite Transmission: When an infected mosquito bites a person, the parasites enter the human body. This form is known as a sporozoite.
  • Liver: After entering the body, the sporozoites travel to the liver and infect the liver cells. Here they multiply asexually in large numbers to produce merozoites.

The Erythrocytic Stage:

  • Bloodstream: As soon as merozoites leave the liver cells, they enter the bloodstream. Now, merozoites infect red blood cells and begin asexual reproduction resulting in n number of merozoites. At this stage, an individual experiences malaria-like symptoms.
  • The Sexual Stage: In this stage, a few merozoite-infected red blood cells will mature into sexual forms, commonly referred to as male and female gametocytes.

Whenever an anopheles mosquito bites an infected individual, the gametocytes are taken along with the blood. More and more sexual reproduction takes place, resulting in the formation of mature gametes. They finally fuse to form an oocyst. The oocyst grows, multiplies, and bursts to produce sporozoites. This completes the full circle.

  • Next Person: At this stage, if an uninfected mosquito bites you, it will become infected and can infect others.

Other Modes of Transmission:

  • Perinatal.

  • Through blood transfusion.

  • Sharing infected needles.

How Was Malaria Treated in the Past?

  • In older times, traditional herbal medicines were used to treat malaria.

  • It was in 1820 that two French scientists isolated a substance called quinine from the bark of the cinchona tree. Quinine became the treatment for intermittent fever.

  • In the early twentieth century, when the link between mosquitoes and their parasites was identified, dichlorodiphenyltrichloroethane and other insecticides came into existence.

  • Use of bed nets to protect people while sleeping is another form of vector control.

  • In recent years, antimalarial drugs, including Chloroquine and Artemisinins, have been used.

With All This Development, Why Is Malaria Still a Problem?

The main reason why it is still a problem is the emergence of drug-resistant parasites and insecticide-resistant mosquitoes. Global efforts are made for the prevention of malaria by the development of malaria vaccines that can save many lives and eradicate this plight.

Since malaria is transmitted via a parasite that passes through multiple stages and the parasite can reproduce both sexually and asexually. This poses a unique challenge for vaccine development. But after all efforts, a successful vaccine for malaria has been notably developed.

Malaria Vaccine

Partial Immunity and Development of the Vaccine

The lifecycle of Plasmodium is quite challenging in terms of the development of a vaccine.

The focus should be on which stage to be targeted. Malaria is different from other diseases and their vaccinations because of the lack of sterile immunity. In simple terms, if you become ill from malaria and recover, you can be infected over and over again. The fact is there is no memory of malaria infection in the body. So the infection in the past will not prevent future infection.

There is evidence of naturally acquired immunity seen in malaria. When someone has a history of malaria in the past, they will get a less severe infection this time (partial, acquired immunity).

This is the reason why malaria is so deadly in children under five years of age and the foreigners traveling in such areas. They have not acquired any immunity in the past; thus, contracting the disease results in a severe infection that may be fatal. So for the development of a malaria vaccine, the mechanism of partial immunity has to be considered.

Immunization With Live Attenuated Vaccines

Another concept was immunization with live attenuated parasites (sporozoite form). Hoffman, in 2002, applied this idea to humans and showed that they could use gamma radiation to weaken the sporozoite inside the anopheles mosquitoes and thus protect the humans completely.

Humans were then exposed to the experimental mosquitoes, and it was seen that the sporozoites could travel into the liver but were unable to mature. This results in no illness in the host. This approach was no doubt a good try, but it had two major drawbacks. Firstly it was not cost-effective, and secondly, it was a little impractical to perform on a large scale.

Present-Day Research

Scientists are using technologies to segregate and deliver specific antigens in a vaccine. Since the parasite had three different life stages, three different approaches have been investigated.

  • The Pre-erythrocytic Vaccines -

The pre-erythrocytic vaccine aims at the infectious phase of malaria.

It either prevents the sporozoites from getting into the liver cells or destroys the infected liver cells.

The most important challenge here is time. After the mosquito bites, it takes hardly an hour for the sporozoites to reach the liver. Thus the immune system faces a lack of time to eliminate the parasite.

  • The Erythrocytic Vaccines -

Also referred to as blood-stage vaccines. This vaccine targets stopping the asexual reproduction of parasites in red blood cells. It has been called the blood stage as, during this time, symptoms of malaria appear. A huge number of merozoites are produced during this stage, and the destruction of red blood cells is at its peak. Currently, there are no such vaccines that have been proven successful.

  • The Sexual Stage Vaccine -

And lastly, another type of vaccine aims at the sexual reproduction that occurs in the mosquito gut. This approach aims to kill the vector to stop the further spread of the parasite. It is named a transmission-blocking vaccine. This is not a direct approach as it will not protect the individual directly from the infected parasite but rather stop the continued transmission. Many researchers and scientists are thinking a step ahead by combining multiple approaches to develop a malaria vaccine. Although much progress has been made in the development of the malaria vaccine, it is still an expensive and multidisciplinary effort. Till now, the only approved vaccine is RTS, S with the brand name mosquirix.

Conclusion:

Malaria is a life-threatening infectious disease caused by female anopheles mosquitoes. Malaria vaccines are used in the treatment of malaria. Different trials have been done to develop vaccines based on different parasitic stages. But the only approved vaccine is traded under the brand name of mosquirix. Large-scale use of vaccines has been recommended for children living in malaria-prone areas.

Frequently Asked Questions

1.

Is There a Malaria Vaccine?

There are several vaccines for malaria that are under development or have been approved for use in certain populations. The most advanced malaria vaccine is called RTS, S. This vaccine has been shown to provide partial protection against malaria in young children and has been recommended for pilot implementation in several countries in the region. Other malaria vaccines are also in development and are being tested in clinical trials.

2.

Which Malaria Vaccine Was Developed First?

The first malaria vaccine to be developed was called RTS, S/AS01. The vaccine was designed to protect against Plasmodium falciparum which is the deadliest species of the malaria parasite. RTS, S/AS01 was the first vaccine to be tested in large-scale clinical trials in sub-Saharan Africa, where malaria is most prevalent.

3.

What Age Is the Malaria Vaccine Given?

Malaria is a parasitic disease that is transmitted to people through the bites of infected mosquitoes. It is a serious and sometimes life-threatening disease that is most common in tropical and subtropical regions of the world. Children and expectant mothers are particularly at risk for the parasitic malaria, as they have weaker immune systems and are more susceptible to severe illness and complications from the disease. In fact, according to the World Health Organization (WHO), children under the age of 5 and pregnant women are at the highest risk of contracting malaria and suffering serious illness or death as a result.

4.

How Long Do Immunizations Against Malaria Last?

When administered as a booster, the vaccine candidate offers young children two years of protection, but larger trials are required before it can be carried out. The first dose was given at around nine months of age and subsequent doses were given at intervals of several months thereafter.

5.

Which Malaria Vaccine Works the Best?

One of the vaccines called RTS, S/AS01 has been shown to provide a moderate level of protection against malaria in young children and infants. Another vaccine, called PfSPZ, is still in the early stages of development and has shown promising results in early clinical trials. 
 
It is important to note that no vaccine is 100 percent effective, and even with a vaccine, it is still important to take steps to prevent malaria, such as using insect repellents, wearing long sleeves and pants, and sleeping under mosquito nets.

6.

Where Is the Vaccine for Malaria Given?

The vaccine is typically given to children, as they are most at risk for contracting the disease. It is usually administered as an intramuscular injection through a series of doses, with the doses administered usually at five months of age.

7.

Is There a Malaria Vaccine Available in India?

Yes, there is a malaria vaccine available in India. The vaccine, called RTS, S. It is the first vaccine to show partial protection against malaria in young children and is currently being introduced in pilot projects in three countries in sub-Saharan Africa (Ghana, Kenya, and Malawi). The vaccine is not yet widely available in India, but clinical trials are ongoing, and it is hoped that the vaccine will eventually be made more widely available in the country.

8.

How Can Malaria Be Prevented?

There are several ways to prevent malaria:
- Use insect repellents- Mosquitoes that transmit malaria can be repelled using insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus.
- Wear long sleeves and pants.
- Get vaccinated.
- Use bed nets.
- Use insecticides.
- Antimalarial medication can be taken to prevent malaria if traveling to areas where the disease is prevalent.

9.

Does the Malaria Vaccination Confer Immunity?

There are a few vaccines that have been developed to prevent malaria, and they can provide a high level of immunity against the disease. However, the level of immunity and duration of protection varies among the different vaccines and can depend on several factors, such as the individual's age, overall health, and previous exposure to malaria.
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Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)

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