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Recent results from malaria vaccine clinical trials

Everyone involved in malaria control has a fervent wish a malaria vaccine is found.
 
The following information is taken from an article that appeared in The Pharmaceutical Journal, 9/16 May 2015, Vol 294, No 7861/2, online | URI: 20068442, published online on 6th May 2015.
 
   
 
Summary 
  • The first candidate malaria vaccine to reach phase III clinical trials, RTS,S/AS01, is not as effective at protecting young African children against the disease as was hoped.
  • Episodes of malaria reduced by just over a third (36%) in children who received three doses of RTS,S/AS01 plus a booster.
  • Researchers who conducted the trial say the vaccine is still worth deploying because millions of children could benefit from vaccination in areas of high transmission.
  • Others have said the assertion the vaccine may be worth deploying in some settings because it prevented large numbers of uncomplicated cases was controversial.
 
Detail
  • Episodes of malaria reduced by just over a third (36%) in children who received three doses of RTS,S/AS01 plus a booster, and by 28% in children who did not receive the booster. Vaccine was less effective in infants. No significant protection against severe disease. Meningitis occurred more frequently in children given the vaccine.
  • Researchers who conducted the trial say the vaccine is still worth deploying because millions of children could benefit from vaccination in areas of high transmission.
  • Brian Greenwood, a researcher in tropical medicine at the London School of Hygiene and Tropical Medicine, and involved in the trial, says: “Despite the falling efficacy over time, there is still a clear benefit from RTS,S/AS01. Given that there were an estimated 198 million malaria cases in 2013, this level of efficacy potentially translates into millions of cases of malaria in children being prevented.
  • Adrian Hill, director of the Jenner Institute at the University of Oxford, says the assertion that the vaccine may be worth deploying in some settings because it prevented large numbers of uncomplicated cases was controversial. “There was no impact on malaria mortality and no significant effect on severe malaria: non-significant reductions of just 1% and 10% were observed in the children and infants studied over the full trial period using a three dose regimen. This is clearly lower than the efficacy of impregnated bed nets.
  • New evidence of a rebound in malaria susceptibility after vaccination was “worrying”, he adds. “After 20 months, vaccinated children who were not boosted showed an increased risk of severe malaria over the next 27 months compared with non-vaccinated controls. It should be possible to make the vaccine more effective in some settings, but that will probably increase delivery costs substantially.
  • The safety and efficacy of RTS,S/AS01 is being reviewed by the European Medicines Agency’s (EMA’s) Committee for Medicinal Products for Human Use (CHMP). An opinion is expected in the second half of 2015.
  • If a positive opinion is obtained and the vaccine is pre-qualified by the WHO, malaria endemic countries can then decide whether to license and use the vaccine.
  • The price of the vaccine has yet to be set. GSK committed to setting a price that covers costs of manufacturing the vaccine and a small return of 5% to be reinvested in R&D for next generation malaria vaccines.