GlaxoSmithKline’s RTS,S vaccine must undergo further testing before being rolled out, says World Health Organization panel

The World Health Organization (WHO) has said the RTS,S malaria vaccine should be tested further through a series of pilot studies before it can recommend its widespread use.

Following a large clinical trial that was published earlier this year, RTS,S, also known as Mosquirix, became the first malaria vaccine to be approved by a regulatory agency, when it was given a ‘positive scientific opinion’ by the European Medicines Agency. It was developed by GlaxoSmithKline (GSK) and works by priming the host’s immune system to attack the Plasmodium falciparum malarial parasites when it enters the bloodstream or tries to multiply in the liver.

But the trial, which involved over 15,000 infants and children across seven African countries, delivered only a qualified success. To protect against malaria long term the vaccine must be administered four times – three doses in quick succession followed by a booster 18 months later. Even then, the vaccine was only shown to offer significant long term protection in children aged 5–17 months, and not in younger infants (6–12 weeks). Its effectiveness lessened with time for both age groups.

The WHO’s strategic advisory group of experts on immunization recommends RTS,S should now be trialled in three to five large scale pilot projects involving up to a million children to see if the unusual four-dose vaccination schedule can be integrated into existing regimes. If it cannot, the WHO may ultimately decide not to back the vaccine’s use.