The malaria vaccine we've been waiting for?

C&I Issue 2, 2024

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Phase 3 trials demonstrate record efficacy in the R21/Matrix-M vaccine – but can it pass the ‘ultimate test’?

New hope in the fight against malaria has emerged with the publication of promising results from a large-scale clinical trial of a vaccine.

The R21/Matrix-M vaccine, developed by Oxford University, UK and the Serum Institute of India, demonstrated an impressive 78% efficacy in preventing malaria in young African children over the first year of follow-up. This surpasses the existing RTS,S/AS01 vaccine – the only malaria vaccine currently recommended by the World Health Organization (WHO), which offers 55% efficacy.

Malaria is the cause of more than 600,000 deaths each year, largely among children.

Published in The Lancet on 1 February (doi: 10.1016/S0140-6736(23)02511-4) the Phase 3 trial, encompassing over 4800 children in Burkina Faso, Kenya, Mali, and Tanzania, assessed the vaccine’s safety and effectiveness. The encouraging results showed a consistent efficacy across diverse geographical locations and transmission settings, with no serious adverse events linked to the vaccine.

In addition to the central Oxford-Serum partnership, the vaccine is supported by the European and Developing Countries Clinical Trials Partnership, the Wellcome Trust, and the European Investment Bank. To date, the vaccine has been licensed for use in Ghana, Nigeria and Burkina Faso.

Notably, the Lancet study revealed that the R21/Matrix-M vaccine not only protected against clinical malaria episodes but also potentially reduced asymptomatic infections, offering an important additional layer of defence against the spread of the disease.

The R21/Matrix-M was granted WHO prequalification status in December 2023, making it eligible for procurement by United Nations agencies. The Serum Institute has manufactured 25m doses and established capacity to produce 100m annually, which it will double over the next two years.

‘The continued high efficacy of this new vaccine in field trials is very encouraging,’ said Adrian Hill, chief investigator on the trial. ‘These data support an important role for the R21 vaccine in providing a crucial new tool for malaria control.’

Experts hailed the findings as a significant step forward. Alassane Dicko, principal investigator in Mali, expressed his belief that the vaccine ‘should be very impactful in preventing malaria deaths in African children’.

John C Jacobs, CEO of Novavax – the manufacturer of the vaccine’s adjuvant – emphasised the potential to save lives: ‘Approximately 1300 children die from malaria every day. The R21/Matrix-M Phase 3 data reinforce the potential of this vaccine to protect children against this disease.’

However, as with any new medicine, there are nuances that require consideration. Alena Pance, a genetics specialist at the University of Hertfordshire, UK, highlighted the need for longer-term and wider geographical data, as the current follow-up period is limited.

‘The data shows a slightly lower efficacy in regions with continuous malaria transmission and there is a tendency to weaning off the effect at the 12-month period, which is a bit concerning,’ Pance noted. ‘There is eager expectation to see the longer-term activity of the vaccine and the level of protection in wider areas in Africa and worldwide.’

Despite taking in regional data from four countries, Eleanor Riley, an immunology expert at the University of Edinburgh, UK, noted that the regions with the most intense, perennial malaria transmission were not included, and this will necessitate further evaluation in those challenging environments.

While celebrating the efficacy reported, Riley notes with caution, ‘None of the five sites in the study represents an area of intense, perennial malaria transmission such as is seen – for example – in central Africa. This is the ultimate test of any malaria vaccine.’

If proven over a longer period and in other regions, this new vaccine has the potential to significantly reduce the burden of malaria across Africa and beyond.