Vaccines for preventing malaria.
BACKGROUND
Despite continued efforts to control the disease, malaria remains a major health problem in many regions of the world, especially sub-Saharan Africa, and new ways to control or eradicate the disease are urgently needed. Two types of vaccine, SPf66 vaccine against the asexual stages, and NANP vaccines against the sporozoite stages of the Plasmodium parasite, have been tested in randomised clinical trials in endemic areas.


OBJECTIVE
To assess the effects of malaria vaccines.


METHODS
The Cochrane Infectious Diseases Group trials register, the Cochrane Controlled Trials Register, Medline, Embase and reference lists of articles were searched. Organisations and researchers in the field were contacted.


METHODS
Randomised trials comparing vaccines against Plasmodium falciparum, P. vivax, P. malariae or P. ovale, and placebo.


METHODS
Two independent reviewers assessed trial quality and conducted data extraction.


RESULTS
Thirteen efficacy trials involving about 7700 people were included. There were nine trials of the Spf66 vaccine and four trials of the NANP vaccines. There was large heterogeneity between trials when investigating the effect of SPf66 in reducing incidence of the first attack of P. falciparum malaria. When trials were subcategorised by location, there was no evidence for effect of SPf66 in reducing incidence of P. falciparum in four African trials conducted in children under 5 years of age (Peto odds ratio [OR] = 0.96, 95% confidence interval [CI] 0.81 to 1.14). In five trials outside Africa with participants aged 2 years to adult, there was a reduction in incidence by SPf66 vaccine (Peto OR = 0.77, 95% CI 0.67 to 0.88, fixed effects model). Significant heterogeneity remained between trials conducted outside Africa. Using a random effects model for these five trials, the OR was 0.74 (95% CI 0.54 to 1.01). In five trials, there was no evidence for effect of the SPf66 vaccine on the incidence of the first attack of P. vivax malaria (OR 1.01, 95% CI 0.87 to 1.17). Trials to date have not indicated any severe adverse effects of SPf66 vaccine. In three trials of NANP-based vaccines, there was no evidence for protection by these vaccines against P. falciparum malaria (OR 1.12, 95% CI 0.64 to 1.93).


CONCLUSIONS
There is no evidence for protection by SPf66 vaccines against P. falciparum in Africa. There is a modest reduction in attacks of P. falciparum malaria following vaccination with SPf66 in other regions. Further research with SPf66 vaccines in South America may be justified. Trials to date have not been of sufficient size to evaluate the effect of malaria vaccines on mortality or on severe malaria requiring admission to hospital. There was not enough evidence to evaluate the use of NANP vaccines.
Graves
P
P
Dept of Preventive Medicine & Biometrics, University of Colorado Health Sciences Center, Box C 245, 4200 E Ninth Ave, Denver, CO 80262, USA. Patricia.Graves@uchsc.edu
Gelband
H
H
D000328:Adult; D006801:Humans; D008288:Malaria / Q000517:prevention & control*; D017780:Malaria Vaccines / Q000627:therapeutic use*; D016778:Malaria, Falciparum / Q000517:prevention & control; D015800:Protozoan Proteins / Q000627:therapeutic use; D011994:Recombinant Proteins
D017780:Malaria Vaccines; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C066269:SPf66 protein, Plasmodium