Conceptually, vaccines are very simple things– Dummy viruses/bacteria/pathogen that train your immune system how to fight the real viruses/bacteria/pathogen. All the benefits of being sick (training your B- and/or T-cells how to fight the pathogen) without actually having to get sick.
In practice, however, things are infinitely more difficult. Sometimes we use dead viruses. Sometimes we use crippled viruses. Sometimes we dont need to use whole viruses at all– little chunks of the virus are fine. Sometimes we just need chunks of the virus, but we keep them dressed up in hollow membranes.
We have no idea what will work on the front end.
And sometimes none of the approaches that worked for other pathogens, works for the new target. HIV-1 is a prime example. TB is another. And, so is malaria.
The WHO estimates that malaria infects 225 million, and kills 781,000 people each year. 92% of those who die of malaria are African children. To put this number in perspective, in 2009 malaria killed more African children than heart disease killed US adults. What if someone suddenly discovered a way to decrease the burden of heart disease by half? Well, today we hear of an intervention that has the potential to achieve a feat of a similar scale in Africa: a malaria vaccine.
Ideally, we want a vaccine like HPV, which is virtually 100% effective at stopping HPV cervical cancers. But we are to the point in HIV-1, TB, malaria (Im sure some Im forgetting) where we will totally take 50% efficacy. Hell, 30% would be a win. Because when you are dealing with millions of infections and in the case of malaria, ~800K deaths, 50% is a lot of suffering averted. A lot of saved lives.
So scientists are rightly pumped about the results of a recent malarial vaccine trial in African kids (the ones most likely to die from malarial infections):
During 12 months of follow-up in the first 6000 children in the older age category, the incidence of the first or only episode of clinical malaria meeting the primary case definition was 0.44 per person-year in the RTS,S/AS01 group and 0.83 per person-year in the control group, resulting in a vaccine efficacy of 55.8% (97.5% confidence interval [CI], 50.6 to 60.4).
Evaluation of the proportionality of the hazard assumption showed that vaccine efficacy was not constant over time (P<0.001 by Schoenfeld residuals) (Table 9 in the Supplementary Appendix), with vaccine efficacy higher at the beginning than at the end of the follow-up period.
At least one episode of severe malaria that met the primary case definition occurred in 57 of 2830 children (2.0%) in the RTS,S/AS01 group and in 56 of 1466 children (3.8%) in the control group, for a vaccine efficacy of 47.3% (95% CI, 22.4 to 64.2).
Vaccine efficacy against severe malaria in the pooled age categories was 34.8% (95% CI, 16.2 to 49.2).
In the older age category, serious adverse events were reported in 1048 of 5949 children (17.6%; 95% CI, 16.7 to 18.6) in the RTS,S/AS01 group and in 642 of 2974 children (21.6%; 95% CI, 20.1 to 23.1) in the control group (Table 3Table 3Serious Adverse Events after the First Dose of a Study Vaccine in the Intention-to-Treat Population, According to Age Category.).
Similar proportions of children died in each study group.
At least one serious adverse event that was considered to be related to a study vaccine occurred in 11 children in the older age category: 10 of 5949 children in the RTS,S/AS01 group reported 12 events (7 seizures, 3 episodes of pyrexia, 1 episode of myositis, and 1 injection-site reaction) and 1 of 2974 children in the control group reported 1 event (seizure).
Summary– So far, this vaccine works the best we have ever seen of any malaria vaccine. Even though both study and control groups had similar bed-net use, the number of kids who got malaria in the malaria vaccine group (the older kids, who were enrolled first, thus their data is available now) was less than half of what was seen in the control group.
Drawbacks– The protection waned with time, and seizures might be a side-effect in a small percentage of kids.
If this is literally the best we can do, I wouldnt turn my nose up at this vaccine if I had a baby somewhere where malaria was endemic. But I dont think this vaccine is the best we can do– its a really great starting off point. From this vaccine, we can explore how to make it better. Make it 100%, like HPV.
Good on you, malaria folks. I really hope this works out.