Another Malaria Vaccine

Deaths from malaria have been deceasing in recent years, primarily due to insect control. However, a study published last year in the Lancet suggests that the number of deaths has been seriously underestimated, primarily due to under-counting of adult mortality.

Global malaria mortality between 1980 and 2010: a systematic analysis.
Murray CJ,et al. Lancet. 2012 Feb 4;379(9814):413-31

FINDINGS:  Global malaria deaths increased from 995,000 (95% uncertainty interval 711,000-1,412,000) in 1980 to a peak of 1,817,000 (1,430,000-2,366,000) in 2004, decreasing to 1,238,000 (929,000-1,685,000) in 2010. In Africa, malaria deaths increased from 493,000 (290,000-747,000) in 1980 to 1,613,000 (1,243,000-2,145,000) in 2004, decreasing by about 30% to 1,133,000 (848,000-1,591,000) in 2010. Outside of Africa, malaria deaths have steadily decreased from 502,000 (322,000-833,000) in 1980 to 104,000 (45,000-191,000) in 2010. We estimated more deaths in individuals aged 5 years or older than has been estimated in previous studies: 435,000 (307,000-658,000) deaths in Africa and 89,000 (33,000-177,000) deaths outside of Africa in 2010.

Progress is being made, but our starting point is much higher than we thought. Vaccines have proven to be the most effective method of controlling disease, so  efforts have been underway for decades to develop malaria protection.

Back in 2011, I wrote about a vaccine against malaria that had been showing promise. Unfortunately, it has not lived up to early expectations, and will probably not be a major player in the fight.

Now, researchers have brought a new vaccine forward for testing (technical details have been published in Science).   The team from Sanaria, a company based in Rockville, Maryland, led by veteran malaria researcher Stephen Hoffman, has taken a different approach than most previous efforts. In the past, efforts have concentrated on recombinant-subunit vaccines containing just a handful of parasite proteins. Hoffman’s team decided to focus on a whole-sporozoite vaccine.

Very early results have been positive, providing 100% resistance, albeit in only 6 patients.

The trial now needs to be repeated and extended in regions where malaria is rampant to test whether it provides protection against different strains of the parasite than that used in the vaccine, and to see how it performs in different age groups, including young children. The first trials will be carried out at the Ifakara Health Institute in Tanzania.

The development team faced some very technical issues in obtaining the sporozoites in enough quantity to be useful.

But to make PfSPZ was challenging. Sanaria succeeded in raising mosquitoes in sterile conditions on an industrial scale, feeding them blood infected with the malaria parasite and then irradiating them to weaken the parasite so that it can still infect people but not cause disease.

Billions of parasites were then harvested from the mosquitoes’ salivary glands, purified and cryopreserved. Many researchers were highly sceptical that sporozoites could be mass-produced in a way that passed the strict quality and safety standards needed for human medicines, notes Fauci. “To my amazement, Hoffman did it,” he adds.

If the vaccine is proven to be useful in the field there are other technical issues to be overcome. This vaccine must be given intravenously, rather than orally or just under the skin. This requires more expertise and slows down the vaccination process. In addition, the vaccine must be stored in liquid nitrogen which may make distribution in remote areas problematic. It will take several years to wend its way through the approval process, and logistical issues will be considered simultaneously.




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