After over 25 years of failed formulas, an HIV vaccine has, for the first time, displayed the ability to confer some immunity against the virus. Deployed in a clinical trial in Thailand, the vaccine managed to prevent infection in a significant minority of volunteers. However, scientists involved in the study caution that they cannot fully explain the success, and that the vaccine only worked in a portion of those who received it.
Even this small success is cause for celebration. Until now, no vaccine has even worked in the slightest, so any protection, even if only amongst a minority of recipients, represents a major breakthrough.
The clinical trial involved 16,402 volunteers, half of whom received vaccine doses in 2006. After three years of monitoring for HIV, 74 of the volunteers who got the placebo contracted the virus, as compared with 51 of those who got the vaccine. At that rate, the vaccine was 31.2 percent effective, not the 70 to 80 percent effectiveness displayed in most licensed vaccines.
The vaccine itself combines two previously tested vaccines, both of which failed on their own. Why those vaccines seemed to have worked in concert, but not alone, continues to vex the researchers. Additionally, volunteers who received the vaccine, but still contracted HIV, showed the same virus count as those who got the placebo. Generally, even a failed vaccine manages to lower the virus level.
One thing the researchers are sure of is that the vaccine does not mimic the immune systems of the rare portion of the population that can contract HIV without developing AIDS.
In many ways, this trial raises more questions than it answers. However, as the first success of a vaccine against the disease, those are questions the medical community is excited and eager to answer.
[via the New York Times]
"The clinical trial involved 16,402 volunteers, half of whom received vaccine doses in 2006. After three years of monitoring for HIV, 74 of the volunteers who got the placebo contracted the virus, as compared with 51 of those who got the vaccine. At that rate, the vaccine was 31.2 percent effective, not the 70 to 80 percent effectiveness displayed in most licensed vaccines."
post hoc, ergo propter hoc
I detect some false logic here. This would only be true if the same number of volunteers came in contact with the virus.
Yes, but you can't ethically exspose 16,000 people to HIV, even in Thailand.
I think that the numbers are a little too close to consider it a success... i mean 70/8,000 and 51/8,000, this is much too little data to really get some results.... maybe if you monitered 16,000 people in thailand and exactly 140 got HIV but otherwise this really cant be proven effective.
I agree with Kuxir
There is not a large enough sample to determine any causality. Statistically 51 and 70 is to small of a sample to meet the minimal confidence interval. In other words, they need several hundred (200 to 400) contracted cases in the test sample and control sample to get a significant result. Size of the sample (8,000) is not relevant. Although I am hopeful this might work! Cross your fingers!
Dr. Brian Glassman
No, a larger sample size is not justification for causation. It still wouldn't factor in the number of people (control & vaccine)who came into contact with the virus.