New Malaria Vaccine Proven Effective in Phase 3 Study

A new malaria vaccine has protected children under the age of 1.5 years against infection with an efficacy of 68%-75% in a phase 3 study. The highest level of vaccine protection was observed in areas with seasonal malaria. The new vaccine’s efficacy is similar to that of the already approved vaccine and could help meet the enormous demand for malaria vaccines.

“Young children are most at risk of severe cases of malaria once the passive protection provided by the mother’s antibodies diminishes. Malaria mortality is highest around the time of the first birthday,” said Beate Kampmann, MD, PhD, director of the Institute of Global Health at Charité — Universitätsmedizin in Berlin. “Therefore, this age group is the right target for vaccinations. Furthermore, the vaccine induced the best immune responses in this age group.”

An estimated 200 million people worldwide contract malaria each year. Of these patients, 600,000 die, including 450,000 children under the age of 5 years. In addition to chemoprophylaxis, mosquito nets, and insect repellents, vaccination is an important preventive approach to curbing the infectious disease.

In 2021, the World Health Organization (WHO) recommended the malaria vaccine RTS,S/AS01, which was developed by GlaxoSmithKline, for wide use. In the approval study, this vaccine demonstrated a vaccine efficacy of 56%.

Research at Oxford 

The new malaria vaccine, R21/Matrix-M, was developed by the University of Oxford, Oxford, United Kingdom. Some African countries have already approved it for malaria prevention. In the Lancet, Mehreen Datoo, MD, DPhil, of the Centre for Clinical Vaccinology and Tropical Medicine at the University, and colleagues reported that a vaccine efficacy of 68%-75% was achieved in a phase 3 study.

For malaria vaccines, high efficacy is acknowledged when 50% of vaccinated individuals are protected from clinical infection. “Due to the much more complicated structure of malaria parasites, compared with, for example, a measles virus, one cannot expect ‘sterilizing immunity,’ that is, nearly 100% reduction in the risk of illness,” said Martin Grobusch, MD, PhD, head of the Centre for Tropical and Travel Medicine at the Amsterdam University Medical Center, Amsterdam, The Netherlands.

In the study, researchers examined the efficacy of the new malaria vaccine in more than 4800 children in Burkina Faso, Mali, Kenya, and Tanzania. Children aged 5-36 months were included, and the average age of the study population was 19 months. The areas where the children lived varied in malaria prevalence. Some regions have seasonal malaria, and others have year-round transmission.

Comparing With Rabies Vaccine

Two-thirds of the children received three doses of R21/Matrix-M at 4-week intervals, along with a booster vaccination 12 months after the third dose. The other children, forming the control group, received rabies vaccinations at the same intervals. They were observed for 12-18 months after vaccination.

In areas affected seasonally, vaccine efficacy reached 75%, and in areas affected year-round, it was 68%. The vaccine was much more effective in children aged 5-17 months compared with those aged 18-36 months, the authors reported. 

They highlighted a higher efficacy of R21/Matrix-M compared with RTS,S/AS01 and noted that the new vaccine is cheaper and can be produced in larger quantities. However, according to the WHO, neither vaccine is superior to the other. 

The new vaccine, R21/Matrix-M, is closely related to the already approved RTS,S/AS01 vaccine. The sequence of the sporozoite surface antigen CSP was directly adopted from the RTS,S/AS01 vaccine, with only the contained amount increased. Another difference is the adjuvant; it is the saponin adjuvant Matrix-M from the company Novavax.

Small Modifications, Increased Efficacy

“These modifications resulted in protection rates in the respective studies that were not achieved on average with the established RTS,S/AS01 vaccine,” said Grobusch. “However, this does not mean that on a large-scale deployment, the new vaccine is fundamentally superior to the old vaccine, as many influencing factors limit the direct comparison between studies.”

Other factors played an important role in efficacy, such as whether additional protective measures such as chemoprophylaxis, mosquito nets, and spray were used, and which areas were investigated. “Only if both vaccines were tested against each other in a joint study could statements be made about which vaccine, in exactly the setting in which the study is conducted, might be superior to the other,” explained Grobusch. “However, this question is to some extent moot because we need multiple vaccines to meet the exorbitant demand.”

Both Vaccines Necessary

Since October 2023, the WHO has recommended both vaccines equally for malaria prevention in children. The choice of vaccine should depend on the specifics of the respective vaccination program, as well as the availability and costs of the vaccines.

Grobusch assessed the safety of the new vaccine as high, comparable to that of the older RTS,S/AS01 vaccine. “All previous studies have not raised significant concerns regarding vaccine tolerability and safety,” he said. As with vaccination, side effects such as pain at the injection site, discomfort, and possibly a febrile reaction may occur.

“The safety data we have from the studies so far do not give cause for concern,” said Kampmann. However, she noted that rare side effects, defined as occurring only in 1 in 10,000 or 1 in 1,000,000 cases, cannot be extensively captured even in a phase 3 study. “Therefore, it is important to have good pharmacovigilance procedures after the introduction of all new vaccines. This vaccine does not differ from others in this regard.”

Good Acceptance Expected

The physician saw no problems with the acceptance of malaria vaccine programs in countries affected by the infectious disease. “People in malaria-endemic areas do not wish for any vaccine more urgently than against this disease, which they still experience personally and in their families on a daily basis. Therefore, I see no major difficulties regarding acceptance.” The same has also been true with vaccinations against meningitis and pneumonia.

The WHO estimates that “the widespread introduction of the two malaria vaccines could potentially save tens of thousands of young lives each year.”

This story was translated from the Medscape German edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.

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Publish date : 2024-02-12 09:09:20

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