EDITORIAL 1: Vaccine hope in malaria fight
Context
The Indian Council of Medical Research (ICMR) has announced a promising candidate vaccine for malaria, which it will now further develop, test and manufacture for commercial purposes in partnership with private companies.
The vaccine
- Known as AdFalciVax, the vaccine mainly targets two parts of Plasmodium falciparum, a pathogen that is the most common source of malaria in humans.
- In India, however, the disease is caused by Plasmodium vivax against which AdFalciVax is ineffective.
Why is this development significant?
- Malaria is a parasitic infection transmitted by mosquitoes, typically causing symptoms such as fever, chills, night sweats, nausea, vomiting, and diarrhoea.
- In some cases, it can lead to severe complications such as seizures, fluid in the lungs, organ damage, and death.
- Having claimed millions of lives, malaria has been one of the deadliest diseases in human history.
- Currently, the disease kills about four lakh people annually, according to World Health Organization (WHO) figures.
- Malaria is most endemic in Africa — Nigeria, Congo, Tanzania, Mozambique, Niger, and Burkina Faso together account for more than half the yearly deaths.
- The disease is also present in India, although malaria deaths have sharply reduced in the country in recent years.
- According to the National Vector Borne Disease Control Programme (NVBDCP), reported malaria deaths stood at 1,151in 1995, and came down to only 93 in 2020 and 83 in 2022.
- The organisation’s ‘World Malaria Report’ says there were 5,511 deaths due to the disease in India in 2022.
- This discrepancy is due to WHO providing estimates and NVBDCP providing only the number of confirmed deaths, which may not have been officially reported.
How does AdFalciVax work?
- AdFalciVax is a chimeric recombinant vaccine — a type of vaccine that uses different parts of the genes of a pathogen (in this case, Plasmodium) to create target proteins that trigger an immune response after being injected.
- AdFalciVax uses two types of target proteins to prevent the spread of infection in two different ways.
- It uses the circumsporozoite protein (CSP) to prevent infection in the person who has been immunised.
- The CSP is produced during the sporozoite stage (when a parasite can infect a new host) and the liver stage (when a parasite enters liver cells, multiplies, and then infects red blood cells) of the parasite.
- Any immune response generated against these stages protects the immunised person from getting the infection.
- The vaccine also uses the Pro6C protein, a fusion of parts of two different proteins — Pfs230 and Pfs48/45 — produced by Plasmodium falciparum. This protein prevents the spread of infection in the community.
- The Pro6C protein stops further spread of the disease by disrupting the lifecycle of the pathogen.
- It disrupts the development of the parasite in the midgut of a mosquito preventing further transmission.
What are the advantages of AdFalciVax?
- Unlike AdFalciVax, RTS,S and R21 only use the CSP protein, and can prevent infection only in vaccinated persons.
- Unlike AdFalciVax, RTS,S and R21 vaccines also do not use full-length CSP proteins. This is why the ICMR’s candidate vaccine is likely to produce a stronger immune response and better protect against infection.
- Researchers have found that AdFalciVax provided more than 90% protection against infection in mice.
- Studies have also suggested that AdFalciVax produces an immune response that may last longer than that produced by the other two vaccines.
- AdFalciVax also contains an adjuvant — a substance used in vaccines to boost the body’s immune response against the targeted disease — called alum.
- The use of alum is beneficial as it does not pose a risk of causing chronic inflammation, unlike adjuvants such as AS01 and Matrix M, which are used in RTS,S and R21.
- Alum is also known to be reliable, and has been used in numerous vaccines used in childhood immunisation programs over the years.
- Another advantage is that alum in AdFalciVax can remain stable at room temperature for at least nine months, according to initial studies.
- This might make it possible to transport the vaccines without maintaining the cold chain.
Conclusion
AdFalciVax marks a significant step toward malaria elimination, but its success depends on swift deployment, continued research, and inclusive strategies targeting all malaria-causing strains.