New Hope for Malaria Vaccine

In Context 

The Malaria vaccine named RTS,S/AS01 (Mosquirix) has modest efficacy and reduces severe Malaria cases by only about 30 per cent after four doses given to children under age 5.

•  It still provides significant public health benefits, and could save thousands of lives every year.

About the vaccines 

• RTS,S/AS01 was developed by GlaxoSmithKline for immunising children.
  • It fails to meet the WHO’s own benchmark for malaria vaccine efficacy of 75 per cent set in 2015. 
• In September 2021, another malaria vaccine, R21/Matrix M, developed by the University of Oxford in the UK, demonstrated an efficacy of 77 per cent in phase 1 and 2 trials among 450 children in Burkina Faso.

• Similarities between both the vaccines : RTS,S and R21 are similar in that they both contain the same part of a major protein that is found on the surface of the liver stage parasite, called sporozoite.
  • Both also contain hepatitis B virus surface antigen (HBsAg), a protein that has an ability to self-assemble and that helps as the formation of virus-like particles of the CSP antigen fused with it.
• Difference: The important difference between the two vaccines is in the amount of the HBsAg. 
  • RTS,S has about 20 percent of the fusion protein, with the remaining 80 percent made up of HBsAg antigen, produced separately. 
  • R21, on the other hand, is made up entirely of the CSP fusion protein moieties, resulting in a much higher proportion of CSP antigen displayed on the virus-like particle surface, which significantly raises its exposure to the immune system of the host.
  • RTS,S is formulated with an adjuvant called AS01 developed at GSK; 
    • R21 employs an adjuvant called Matrix-M developed by Novavax (Sweden).
    • Matrix M contains saponin-plant based material and stimulates both antibody and cellular immune responses to vaccines. 
• Efficiency : Both adjuvants have shown high levels of efficacy and safety. Matrix-M has been used in a variety of vaccine formulations against influenza, and more recently in the Novovax Covid-19 vaccine.

• Recent Results : The recent results of a booster dose of R21 have created well-deserved excitement, the results of a larger phase 3 trial of the vaccine will be keenly awaited. 
  • The first results are expected by the end of 2023.
• India: weakness and strength: A major gap is in the establishment of safe and scientifically robust control human infection models in India for diseases like malaria or influenza. 

• All malaria vaccines under development need to be tested in the safe and scientific robust Controlled Human Malaria Infection (CHMI) model after completing phase 1 safety studies.
  •  This has been established in many countries of Europe, the UK, Colombia, and Thailand. 
    • Both RTS, S and R21 were tested in CHMI before further safety and efficacy field trials.

• Scientists at the International Centre for Genetic Engineering and Biotechnology (ICGEB) Delhi have carried out phase 1 safety trials of two experimental blood stage malaria vaccines developed and produced in the country.
  •  But further development of these vaccines has been a challenge in the absence of the CHMI model in India.
• Future Prospects : The road ahead is long, but R21, alone or in combination with an efficacious blood stage or transmission stage vaccine candidate, can continue to be developed to achieve the ultimate goal of malaria eradication. 
  •  Scientific, long term continuous funding, regulatory and logistic processes need to be better coordinated to assist scientists in the development of novel vaccines against infectious diseases. 
  • With a highly successful and deeply committed vaccine-producing biopharma industry and a strong scientific base, India should be able to lead the world in developing and producing vaccines.

Source:IE