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Good news on malaria vaccines

By tlambert on December 9, 2008.

The NEJM reports some extremely promising results on a vaccine against malaria:

In this trial, RTS,S was given along with other vaccines for children (a vaccine containing diphtheria and tetanus toxoids, whole-cell pertussis vaccine, and conjugated Haemophilus influenzae type b vaccine), according to the Expanded Program on Immunization (EPI) schedule. There was no interference with immune responses to the EPI vaccines. This result suggests that it will be feasible to provide RTS,S together with other routine children's vaccines, making its delivery in endemic areas much easier and less costly. During the 6-month period after immunization, the incidences of malarial infection and clinical disease in the RTS,S group were reduced by 65% and 59%, respectively.

If the vaccine works in wider trials, combined with insecticide-treated nets and artemisinin-based drugs there is a real prospect of eradicating malaria.

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I'll have to send this post to my sister who had claimed that vaccines don't really work. That's what she has been told by her chiropractor. e.g. Polio was on the decline anyway.

Oh no! I foresee a terrible alliance between the anti-vaxers and the pro-DDT mob... Can the internets stand it?

Bah. Dunc beat me to it.

Best,

D

This is wonderful news.

Still, can someone explain why the efficacy might be good enough to raise "a real prospect of eradicating malaria"? They found a reduction in incidence of clinical disease for the six month period of 59%. I get that there are network effects so that the reduction in disease is greater than the efficacy of the vaccine. Still, intuitively, that doesn't sound that high to me. Furthermore, presumably the efficacy will taper off as the child ages (or is that not how it works?). And surely Plasmodium falciparum won't take it lying down either and will evolve to reduce the efficacy over time.

An interesting tidbit from the article: This vaccine works strictly on the liver part of the life cycle of the parasite. From the NEJM article:

Thus, if immune responses generated by "leaky" pre-erythrocytic vaccines such as RTS,S fail to block just a single sporozoite from invading or developing in the hepatocyte, then a blood-stage infection will follow, and typical paroxysmal fevers and, perhaps, severe malarial disease will manifest.

I don't know if there are any candidates for vaccines that work against the blood-stage infection, but even a relatively ineffective one might be powerful in combination with this vaccine.

if it works, will this eradicate malaria or the affects of malaria on humans?

Crust, as far as I'm aware the only malaria vaccines that are currently in advanced clinical trials target the liver stage of the parasite.

There are a few blood stage vaccines under development that show promise, but it will be several years before clinical trial data is available
[link](http://www.malariavaccine.org/rd-research-programs.php#latrobe)
[link](http://www.pro-test.org.uk/b2evo/index.php?blog=7&title=a_new_malaria_v…)

sjk:

[I]f it works, will this eradicate malaria or the affects of malaria on humans?

According to Wikipedia, malaria only infects humans:

The malaria parasites do not affect animal species and therefore eradication of the disease from the human population would be expected to be effective.

Thanks, Paul. Do you have an opinion on whether this efficacy rates are sufficient to have a real chance of eradicating malaria? Even putting aside factors that would erode the efficacy (e.g. resistance developing in the parasite), I wonder if reducing incidence by a little over half would be enough to do the trick.

According to Wikipedia, malaria only infects humans:

The species which infect humans (Plasmodium vivax and P. falciparum) only infect humans, as I recall. However, there are a lot of other malaria species which infect other host species, generally with less specificity. These don't infect humans.