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The Journal of Clinical Investigation Jan 2022
Review
Topics: Humans; Malaria Vaccines; Malaria, Falciparum; Plasmodium falciparum
PubMed: 34981788
DOI: 10.1172/JCI156588 -
BioDrugs : Clinical Immunotherapeutics,... Nov 2023Malaria is a mosquito-borne disease caused by protozoan parasites of the genus Plasmodium. Despite significant declines in malaria-attributable morbidity and mortality... (Review)
Review
Malaria is a mosquito-borne disease caused by protozoan parasites of the genus Plasmodium. Despite significant declines in malaria-attributable morbidity and mortality over the last two decades, it remains a major public health burden in many countries. This underscores the critical need for improved strategies to prevent, treat and control malaria if we are to ultimately progress towards the eradication of this disease. Ideally, this will include the development and deployment of a highly effective malaria vaccine that is able to induce long-lasting protective immunity. There are many malaria vaccine candidates in development, with more than a dozen of these in clinical development. RTS,S/AS01 (also known as Mosquirix) is the most advanced malaria vaccine and was shown to have modest efficacy against clinical malaria in phase III trials in 5- to 17-month-old infants. Following pilot implementation trials, the World Health Organisation has recommended it for use in Africa in young children who are most at risk of infection with P. falciparum, the deadliest of the human malaria parasites. It is well recognised that more effective malaria vaccines are needed. In this review, we discuss malaria vaccine candidates that have progressed into clinical evaluation and highlight the most advanced candidates: Sanaria's irradiated sporozoite vaccine (PfSPZ Vaccine), the chemoattenuated sporozoite vaccine (PfSPZ-CVac), RTS,S/AS01 and the novel malaria vaccine candidate, R21, which displayed promising, high-level efficacy in a recent small phase IIb trial in Africa.
Topics: Infant; Animals; Child; Humans; Child, Preschool; Malaria Vaccines; Plasmodium falciparum; Malaria, Falciparum; Malaria; Sporozoites
PubMed: 37728713
DOI: 10.1007/s40259-023-00623-4 -
Lancet (London, England) Feb 2024Recently, we found that a new malaria vaccine, R21/Matrix-M, had over 75% efficacy against clinical malaria with seasonal administration in a phase 2b trial in Burkina... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Recently, we found that a new malaria vaccine, R21/Matrix-M, had over 75% efficacy against clinical malaria with seasonal administration in a phase 2b trial in Burkina Faso. Here, we report on safety and efficacy of the vaccine in a phase 3 trial enrolling over 4800 children across four countries followed for up to 18 months at seasonal sites and 12 months at standard sites.
METHODS
We did a double-blind, randomised, phase 3 trial of the R21/Matrix-M malaria vaccine across five sites in four African countries with differing malaria transmission intensities and seasonality. Children (aged 5-36 months) were enrolled and randomly assigned (2:1) to receive 5 μg R21 plus 50 μg Matrix-M or a control vaccine (licensed rabies vaccine [Abhayrab]). Participants, their families, investigators, laboratory teams, and the local study team were masked to treatment. Vaccines were administered as three doses, 4 weeks apart, with a booster administered 12 months after the third dose. Half of the children were recruited at two sites with seasonal malaria transmission and the remainder at standard sites with perennial malaria transmission using age-based immunisation. The primary objective was protective efficacy of R21/Matrix-M from 14 days after third vaccination to 12 months after completion of the primary series at seasonal and standard sites separately as co-primary endpoints. Vaccine efficacy against multiple malaria episodes and severe malaria, as well as safety and immunogenicity, were also assessed. This trial is registered on ClinicalTrials.gov, NCT04704830, and is ongoing.
FINDINGS
From April 26, 2021, to Jan 12, 2022, 5477 children consented to be screened, of whom 1705 were randomly assigned to control vaccine and 3434 to R21/Matrix-M; 4878 participants received the first dose of vaccine. 3103 participants in the R21/Matrix-M group and 1541 participants in the control group were included in the modified per-protocol analysis (2412 [51·9%] male and 2232 [48·1%] female). R21/Matrix-M vaccine was well tolerated, with injection site pain (301 [18·6%] of 1615 participants) and fever (754 [46·7%] of 1615 participants) as the most frequent adverse events. Number of adverse events of special interest and serious adverse events did not significantly differ between the vaccine groups. There were no treatment-related deaths. 12-month vaccine efficacy was 75% (95% CI 71-79; p<0·0001) at the seasonal sites and 68% (61-74; p<0·0001) at the standard sites for time to first clinical malaria episode. Similarly, vaccine efficacy against multiple clinical malaria episodes was 75% (71-78; p<0·0001) at the seasonal sites and 67% (59-73; p<0·0001) at standard sites. A modest reduction in vaccine efficacy was observed over the first 12 months of follow-up, of similar size at seasonal and standard sites. A rate reduction of 868 (95% CI 762-974) cases per 1000 children-years at seasonal sites and 296 (231-362) at standard sites occurred over 12 months. Vaccine-induced antibodies against the conserved central Asn-Ala-Asn-Pro (NANP) repeat sequence of circumsporozoite protein correlated with vaccine efficacy. Higher NANP-specific antibody titres were observed in the 5-17 month age group compared with 18-36 month age group, and the younger age group had the highest 12-month vaccine efficacy on time to first clinical malaria episode at seasonal (79% [95% CI 73-84]; p<0·001) and standard (75% [65-83]; p<0·001) sites.
INTERPRETATION
R21/Matrix-M was well tolerated and offered high efficacy against clinical malaria in African children. This low-cost, high-efficacy vaccine is already licensed by several African countries, and recently received a WHO policy recommendation and prequalification, offering large-scale supply to help reduce the great burden of malaria in sub-Saharan Africa.
FUNDING
The Serum Institute of India, the Wellcome Trust, the UK National Institute for Health Research Oxford Biomedical Research Centre, and Open Philanthropy.
Topics: Child, Preschool; Female; Humans; Infant; Male; Antibodies, Viral; Burkina Faso; Double-Blind Method; Immunization; Malaria; Malaria Vaccines; Nanoparticles; Saponins
PubMed: 38310910
DOI: 10.1016/S0140-6736(23)02511-4 -
Nature Microbiology Nov 2021A promising vaccine fails to provide durable protection against infection and clinical malaria in infants, a key malaria vaccine target population, in a phase 2b...
A promising vaccine fails to provide durable protection against infection and clinical malaria in infants, a key malaria vaccine target population, in a phase 2b clinical trial. The need for a highly effective vaccine against malaria remains as urgent as ever.
Topics: Malaria Vaccines
PubMed: 34635830
DOI: 10.1038/s41564-021-00982-0 -
Philosophical Transactions of the Royal... Oct 2011There is no licenced vaccine against any human parasitic disease and Plasmodium falciparum malaria, a major cause of infectious mortality, presents a great challenge to... (Review)
Review
There is no licenced vaccine against any human parasitic disease and Plasmodium falciparum malaria, a major cause of infectious mortality, presents a great challenge to vaccine developers. This has led to the assessment of a wide variety of approaches to malaria vaccine design and development, assisted by the availability of a safe challenge model for small-scale efficacy testing of vaccine candidates. Malaria vaccine development has been at the forefront of assessing many new vaccine technologies including novel adjuvants, vectored prime-boost regimes and the concept of community vaccination to block malaria transmission. Most current vaccine candidates target a single stage of the parasite's life cycle and vaccines against the early pre-erythrocytic stages have shown most success. A protein in adjuvant vaccine, working through antibodies against sporozoites, and viral vector vaccines targeting the intracellular liver-stage parasite with cellular immunity show partial efficacy in humans, and the anti-sporozoite vaccine is currently in phase III trials. However, a more effective malaria vaccine suitable for widespread cost-effective deployment is likely to require a multi-component vaccine targeting more than one life cycle stage. The most attractive near-term approach to develop such a product is to combine existing partially effective pre-erythrocytic vaccine candidates.
Topics: Adjuvants, Immunologic; Animals; Antigens, Protozoan; Clinical Trials as Topic; Culicidae; Drug Design; Humans; Immunity, Cellular; Malaria Vaccines; Malaria, Falciparum; Plasmodium falciparum; Sporozoites; Vaccination; Vaccines, Subunit
PubMed: 21893544
DOI: 10.1098/rstb.2011.0091 -
Immunological Reviews Jan 2020Developing efficacious vaccines for human malaria caused by Plasmodium falciparum is a major global health priority, although this has proven to be immensely challenging... (Review)
Review
Developing efficacious vaccines for human malaria caused by Plasmodium falciparum is a major global health priority, although this has proven to be immensely challenging over the decades. One major hindrance is the incomplete understanding of specific immune responses that confer protection against disease and/or infection. While antibodies to play a crucial role in malaria immunity, the functional mechanisms of these antibodies remain unclear as most research has primarily focused on the direct inhibitory or neutralizing activity of antibodies. Recently, there is a growing body of evidence that antibodies can also mediate effector functions through activating the complement system against multiple developmental stages of the parasite life cycle. These antibody-complement interactions can have detrimental consequences to parasite function and viability, and have been significantly associated with protection against clinical malaria in naturally acquired immunity, and emerging findings suggest these mechanisms could contribute to vaccine-induced immunity. In order to develop highly efficacious vaccines, strategies are needed that prioritize the induction of antibodies with enhanced functional activity, including the ability to activate complement. Here we review the role of complement in acquired immunity to malaria, and provide insights into how this knowledge could be used to harness complement in malaria vaccine development.
Topics: Animals; Antibodies, Protozoan; Complement Activation; Complement System Proteins; Disease Models, Animal; Erythrocytes; Host-Parasite Interactions; Humans; Immunity, Innate; Immunization, Passive; Malaria Vaccines; Malaria, Falciparum; Plasmodium falciparum
PubMed: 31556468
DOI: 10.1111/imr.12802 -
Frontiers in Immunology 2021In areas where transmission is endemic, clinical immunity against malaria is progressively acquired during childhood and adults are usually protected against the severe... (Review)
Review
In areas where transmission is endemic, clinical immunity against malaria is progressively acquired during childhood and adults are usually protected against the severe clinical consequences of the disease. Nevertheless, pregnant women, notably during their first pregnancies, are susceptible to placental malaria and the associated serious clinical outcomes. Placental malaria is characterized by the massive accumulation of infected erythrocytes and monocytes in the placental intervillous spaces leading to maternal anaemia, hypertension, stillbirth and low birth weight due to premature delivery, and foetal growth retardation. Remarkably, the prevalence of placental malaria sharply decreases with successive pregnancies. This protection is associated with the development of antibodies directed towards the surface of -infected erythrocytes from placental origin. Placental sequestration is mediated by the interaction between VAR2CSA, a member of the erythrocyte membrane protein 1 family expressed on the infected erythrocytes surface, and the placental receptor chondroitin sulfate A. VAR2CSA stands today as the leading candidate for a placental malaria vaccine. We recently reported the safety and immunogenicity of two VAR2CSA-derived placental malaria vaccines (PRIMVAC and PAMVAC), spanning the chondroitin sulfate A-binding region of VAR2CSA, in both malaria-naïve and -exposed non-pregnant women in two distinct Phase I clinical trials (ClinicalTrials.gov, NCT02658253 and NCT02647489). This review discusses recent advances in placental malaria vaccine development, with a focus on the recent clinical data, and discusses the next clinical steps to undertake in order to better comprehend vaccine-induced immunity and accelerate vaccine development.
Topics: Animals; Antigens, Protozoan; Drug Development; Female; Host-Parasite Interactions; Humans; Immunization; Immunogenicity, Vaccine; Malaria Vaccines; Malaria, Falciparum; Placenta; Pregnancy; Pregnancy Complications, Parasitic; Treatment Outcome
PubMed: 33717176
DOI: 10.3389/fimmu.2021.634508 -
Frontiers in Immunology 2018The quest for a licensed effective vaccine against malaria remains a global priority. Even though classical vaccine design strategies have been successful for some viral... (Review)
Review
The quest for a licensed effective vaccine against malaria remains a global priority. Even though classical vaccine design strategies have been successful for some viral and bacterial pathogens, little success has been achieved for , which causes the deadliest form of malaria due to its diversity and ability to evade host immune responses. Nevertheless, recent advances in vaccinology through high throughput discovery of immune correlates of protection, lymphocyte repertoire sequencing and structural design of immunogens, provide a comprehensive approach to identifying and designing a highly efficacious vaccine for malaria. In this review, we discuss novel vaccine approaches that can be employed in malaria vaccine design.
Topics: Animals; Humans; Malaria Vaccines; Malaria, Falciparum; Plasmodium falciparum
PubMed: 30555463
DOI: 10.3389/fimmu.2018.02769 -
Parasitology International Oct 2021An estimated 229 million cases of malaria occurred worldwide in 2019. Both, Plasmodium falciparum and P. vivax are responsible for most of the malaria disease burden in... (Review)
Review
An estimated 229 million cases of malaria occurred worldwide in 2019. Both, Plasmodium falciparum and P. vivax are responsible for most of the malaria disease burden in the world. Despite difficulties in obtaining an accurate number, the global estimates of cases in 2019 are approximately 229 million of which 2.8% are due to P. vivax, and the total number of malaria deaths are approximately 409 million. Regional elimination or global eradication of malaria will be a difficult task, particularly for P. vivax due to the particular biological features related to the hypnozoite, leading to relapse. Countries that have shown successful episodes of a decrease in P. falciparum malaria, are left with remaining P. vivax malaria cases. This is caused by the mechanism that the parasite has evolved to remain dormant in the liver forming hypnozoites. Furthermore, while clinical trials of vaccines against P. falciparum are making fast progress, a very different picture is seen with P. vivax, where only few candidates are currently active in clinical trials. We discuss the challenge that represent the hypnozoite for P. vivax vaccine development, the potential of Controlled Human Malaria Challenges (CHMI) and the leading vaccine candidates assessed in clinical trials.
Topics: Animals; Humans; Malaria Vaccines; Malaria, Vivax; Plasmodium vivax
PubMed: 34166786
DOI: 10.1016/j.parint.2021.102411 -
MBio Apr 2016
Topics: Africa; Female; Humans; Infant; Malaria; Malaria Vaccines; Male; Sex Factors
PubMed: 27118593
DOI: 10.1128/mBio.00514-16