First malaria vaccine for children could be recommended for use by autumn

First malaria vaccine for children could be recommended for use by autumn

In sub-Saharan Africa, malaria kills around 1,300 children every day, and as yet there is no licensed vaccine against the disease anywhere in the world.

The vaccine, known as RTS,S/ASO1, seems to be partially effective in young children up to four years after receiving the jab, and could prevent a substantial number of cases of clinical cases of malaria, particularly in areas of high transmission, the results suggest.

The phase III randomised trial enrolled 15,459 infants (aged 6 to 12 weeks at first vaccination) and children aged 5 to 17 months at first vaccination from 11 sites across seven sub-Saharan African countries (Burkina Faso, Gabon, Ghana, Kenya, Malawi, Mozambique and United Republic of Tanzania) with varying levels of malaria transmission.

In 2014, initial phase III results at 18 months showed that the vaccine reduced about 46% and 27%, respectively, of clinical malaria episodes in children and infants.

In this study, members of the RTS,S Clinical Trials Partnership followed up the infants and children for a further 20 to 30 months, and assessed the impact of a fourth booster dose.

Participants were each vaccinated three times with RTS,S/AS01 with or without a booster dose 18 months later, or given four doses of a comparator vaccine.

In children who received the doses of RTS,S/AS01 plus a booster, the number of clinical episodes of malaria at 4 years fell by just over a third (36%). This is lower than the 50% protection seen in the first year. But in children given a booster dose, overall protection against severe malaria was 32%, and 35% against hospital admissions associated with the disease. This was not seen in children not given the booster dose.

In infants given three doses of RTS,S/AS01 plus a booster, the vaccine reduced the risk of clinical episodes of malaria by 26% over three years of monitoring. There was no significant protection against severe disease in infants.

Meningitis was more common in children given RTS,S/AS01 than in those given the comparator vaccine, and it produced more side effects. Convulsions, although rare, occurred more frequently in children given RTS,S/AS01.

If the vaccine receives the thumbs up from the drugs regulator, the European Medicines Agency, the World Health Organisation could recommend the vaccine as early as October this year.

“Despite the falling efficacy over time, there is still a clear benefit from RTS,S/AS01. An average 1,363 cases of clinical malaria were prevented over 4 years of follow-up for every 1,000 children vaccinated, and 1,774 cases in those who also received a booster shot,” explains author Brian Greenwood and Professor of Clinical Tropical Medicine at London School of Hygiene & Tropical Medicine.

“Over three years of follow-up, an average 558 cases were averted for every 1,000 infants vaccinated, and 983 cases in those also given a booster dose,” he adds.

“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,” he says.

In a linked comment**, Vasee Moorthy and Jean Marie Okwo-Bele, from the Department of Immunization, Vaccines and Biologicals at WHO warn: “The donor community would need to coordinate any financing for the RTS,S/AS01 vaccine carefully, should it reach that stage.

“In particular, funding must not be redirected away from meeting adequate access to artemisinin-combination treatments, rapid diagnostic tests, long lasting insecticidal nets, and other malaria control measures already in place in certain settings.

* RTS,S Clinical Trials Partnership. Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial. The Lancet, 2015. Doi: 10.1016/S0140-6736(15)60721-8

** Vasee S Moorthyemail, Jean-Marie Okwo-Bele. Final results from a pivotal phase 3 malaria vaccine trial. The Lancet, 2015. Doi: 10.1016/S0140-6736(15)60767-X




By Caroline White,

OnMedica, Friday 24 April 2015

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