Last updated on September 11th, 2022 at 12:41 pm
Although it may seem like all we talk about are the COVID-19 vaccines, there is a new malaria vaccine developed by Oxford University that has shown a strong effectiveness and safety profile in phase 1/2b clinical trials. Control of malaria has been a goal of scientists for a long time, a potential malaria vaccine is something that should be celebrated widely.
If all goes well, the Oxford malaria vaccine could be approved by late 2023, saving children in many parts of the world from this scourge.
A new paper has been published that provides details of the clinical trial, which I will review below.
What is malaria?
Malaria is caused by a single-celled parasite from one of four related microorganisms in the Plasmodium group. It is carried to humans by an infected female Anopheles mosquito.
Malaria is endemic to tropical areas across the world, including Sub-Saharan Africa, South America, and Asia. However, it used to be prevalent in other areas, such as Southern Europe and Southern USA, until post-World War II eradication efforts, including the use of the environmentally dangerous DDT, eliminated it in those areas. Of course, with climate change, the mosquito vector may spread far beyond its current areas.
Malaria infection develops via two phases – one that involves the liver (exoerythrocytic phase), and one that involves red blood cells, or erythrocytes (erythrocytic phase). When an infected mosquito pierces a person’s skin to take a blood meal, malaria sporozoites in the mosquito’s saliva enter the bloodstream and migrate to the liver where they infect hepatocytes, multiplying asexually and asymptomatically for a period of 8–30 days.
After a potential dormant period in the liver, these organisms differentiate to yield thousands of merozoites, which, following the rupture of their host cells, escape into the blood and infect red blood cells to begin the erythrocytic stage of the life cycle. The parasite escapes from the liver undetected by wrapping itself in the cell membrane of the infected host liver cell.
Within the red blood cells, the parasites multiply further, again asexually, periodically breaking out of their host cells to invade new red blood cells. Several such amplification cycles occur. Thus, classical descriptions of waves of fever arise from simultaneous waves of merozoites escaping and infecting red blood cells.
Malaria symptoms include chills, flu-like symptoms, fever, vomiting, diarrhea, and jaundice. It can be life-threatening if untreated.
Speaking of treatments, malaria is treated with antimalarial medications – the one used depends on the type and severity of the disease.
Malaria vaccine
One of the best methods to prevent malaria is to destroy the mosquito vector, but that brings with it a number of environmental issues. There is ongoing research on a genetically modified mosquito that basically ends the parasite/mosquito life cycle, but we are a long way from that being widely implemented.
There is a malaria vaccine, GlaxoSmithKline Vaccine’s RTS,S/AS01 (RTS,S), that has been approved by the European Medicines Agency. Unfortunately, it has only moderate effectiveness, ranging from 26-50% in children.
The new malaria vaccine developed by Oxford (the same Oxford that developed the COVID-19 vaccine distributed by AstraZeneca), in partnership with Novavax, is known as R21. Though we will review the clinical trial in more detail below, it did show up to 77% effectiveness in a Phase IIb clinical trial of 450 children in Burkina Faso over 12 months.
The researchers also noted that there were “no serious adverse events related to the vaccine.”
The researchers have recruited 4800 children, aged 5-36 months, for a phase III clinical trial to assess large-scale safety and effectiveness across four African countries. The trial is now closed to new participants, so we will await results, probably early in 2023.
Novavax and other pharmaceutical partners are hoping to produce 200 million doses annually which would have a “major public health impact if licensure is achieved.” Given the hundreds of thousands of deaths from malaria among children across the world, this vaccine could be a game-changer.
Oxford malaria vaccine paper
In a paper published on 7 September 2002 in The Lancet, researchers examined the results from a double-blind phase 1/2b randomized controlled trial with 409 children aged 5–17 months in Nanoro, Burkina Faso. Eligible children were enrolled and randomly assigned (1:1:1) to receive three vaccinations of either 5 μg R21/25 μg Matrix-M (n=132), 5 μg R21/50 μg Matrix-M (n=137), or a control vaccine (the Rabivax-S rabies vaccine) (n=140) before the malaria season, with a booster dose 12 months later. The rabies vaccine was used since it had similar components to the malaria vaccine.
The results were very good:
- Vaccine effectiveness (VE) was 71% in the low-dose adjuvant group.
- VE was 80% in the high-dose adjuvant group.
- In the high-dose adjuvant group, VE against multiple episodes of malaria was 78%.
- The researchers estimated that 2,285 cases of malaria were averted per 1000 child-years at risk among vaccinated children in the second year of follow-up.
- At 28 days following the last malaria vaccination, titers of malaria-specific antibodies correlated positively with protection against malaria in both the first year and second year of follow-up.
These results, if confirmed in the large phase 3 clinical trial, are definitely a world-changer in stopping this disease in children. It would quickly stop a debilitating disease that has ravished many parts of the world for centuries.
And for those who adventure travel to areas with endemic malaria, you can probably add this vaccine to your pre-travel checklist of vaccines.
If I haven’t made it clear, this malaria vaccine from Oxford is one of the great medical advances in our era. But I say that about every vaccine since vaccines save lives.
Citations
- Bledsoe GH. Malaria primer for clinicians in the United States. South Med J. 2005 Dec;98(12):1197-204; quiz 1205, 1230. doi: 10.1097/01.smj.0000189904.50838.eb. PMID: 16440920.
- Datoo MS, Natama HM, Somé A, Bellamy D, Traoré O, Rouamba T, Tahita MC, Ido NFA, Yameogo P, Valia D, Millogo A, Ouedraogo F, Soma R, Sawadogo S, Sorgho F, Derra K, Rouamba E, Ramos-Lopez F, Cairns M, Provstgaard-Morys S, Aboagye J, Lawrie A, Roberts R, Valéa I, Sorgho H, Williams N, Glenn G, Fries L, Reimer J, Ewer KJ, Shaligram U, Hill AVS, Tinto H. Efficacy and immunogenicity of R21/Matrix-M vaccine against clinical malaria after 2 years’ follow-up in children in Burkina Faso: a phase 1/2b randomised controlled trial. Lancet Infect Dis. 2022 Sep 7:S1473-3099(22)00442-X. doi: 10.1016/S1473-3099(22)00442-X. Epub ahead of print. PMID: 36087586.
- Vaughan AM, Aly AS, Kappe SH. Malaria parasite pre-erythrocytic stage infection: gliding and hiding. Cell Host Microbe. 2008 Sep 11;4(3):209-18. doi: 10.1016/j.chom.2008.08.010. PMID: 18779047; PMCID: PMC2610487.
