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HIV Vaccine!

Puppycow

Penultimate Amazing
Puppycow
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Combo vaccine reduces risk of HIV infection, researchers say

Unfortunately, it's only about one-third effective, but it's a start.
(CNN) -- A vaccine to prevent HIV infection has shown modest results for the first time, researchers have found.

In what is being called the world's largest HIV vaccine trial ever, researchers found that people who received a series of inoculations of a prime vaccine and booster vaccine were 31 percent less likely to get HIV, compared with those on a placebo.

"Before this study, it was thought vaccine for HIV is not possible," Col. Jerome Kim, who is the HIV vaccines product manager for the U.S. Army, told CNN.

Kim emphasized that the level of efficacy was modest, but given the failures of previous HIV vaccine trials, "yesterday we would have thought an HIV vaccine wasn't possible."

He called the results from the trial an important first step that will help researchers work toward a more effective vaccine.
. . .
"These results show that development of a safe and effective preventive HIV vaccine is possible," said Col. Nelson Michael, who is director of the U.S. military HIV research program.
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How are experiments like these carried out?

It's unethical to inject people with HIV.
 
Kahalachan said:
How are experiments like these carried out?

It's unethical to inject people with HIV.
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You find a population which is already at higher risk for HIV acquisition - a rule of thumb is that you need to expect at least 50 cases in your control group.

Linda
 
Kahalachan said:
How are experiments like these carried out?

It's unethical to inject people with HIV.
Click to expand...
The article suggests that no one was injected with HIV!

This study showed that 9 per 1000 people on the placebo got HIV compared to 6.5 per 1000 on the drug. 16,000 took part but only 125 caught HIV. I am no expert but wonder about the confidence level when so few went on to get the disease. There are no details in the article as to how many of each group were in high HIV risk categories.
While any improvement in preventing HIV is welcome we need to be sure that this drug does have the supposed effect.
 
Lothian said:
The article suggests that no one was injected with HIV!

This study showed that 9 per 1000 people on the placebo got HIV compared to 6.5 per 1000 on the drug. 16,000 took part but only 125 caught HIV. I am no expert but wonder about the confidence level when so few went on to get the disease. There are no details in the article as to how many of each group were in high HIV risk categories.
Click to expand...

This would only matter if you had reason to believe that the group given placebo contained more people at high risk. Randomization should distribute the people who are in high HIV risk categories evenly between the groups. Alternatively, even if the distribution is uneven it is just as likely to be the vaccine group who is at higher risk than it is to be the placebo group (i.e. the vaccine works much better than indicated).

Linda
 
Darat said:
It is good news - just bad that it had to come out of socialist research (sorry I couldn't help myself).
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I don't think this is the sort of research which Beerina is looking for. After all, it will preferentially affect morbidity and mortality in the disenfranchised and the poor. Those are not the deaths she/he has displayed concern about.

Linda
 
fls said:
You find a population which is already at higher risk for HIV acquisition - a rule of thumb is that you need to expect at least 50 cases in your control group.

Linda
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Oh!!!!!!! Hah hah got it. Such a simple solution.

I should've figured this out. :blush:
 
fls said:
This would only matter if you had reason to believe that the group given placebo contained more people at high risk. Randomization should distribute the people who are in high HIV risk categories evenly between the groups.
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It should, but there is a known link between high risk groups and getting the disease. Whether this treatment stops it is not known. The difference seems very low; 0.024% less chance of getting HIV in the treatment group. I wonder if it could be down to other factors than the treatment. I appreciate that there are limits to what can be done to ensure the two groups are similar and that with 16,000 starting this trial I can't really expect a bigger one. It is the confidence factor that I don't understand. Can we say as result of this that we are 100% certain that this treatment lowers the risk or a case where we are only 50% certain?

Alternatively, even if the distribution is uneven it is just as likely to be the vaccine group who is at higher risk than it is to be the placebo group (i.e. the vaccine works much better than indicated).

Linda
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Thanks. Never thought of that.
 
do the participants know what the trial was for? I think this could affect the outcome. Even more so than other trials, since HIV contraction relies highly on a person's actions. Sure, it has equal chance of affecting each group, but this would diminish the confidence level. I would expect that another trial with 100,000 would show no difference at all between inoculation and placebo.
 
Lothian said:
Can we say as result of this that we are 100% certain that this treatment lowers the risk or a case where we are only 50% certain?
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From simple stats, it appears to be the standard 95% confidence level. You never get 100%, and 50% is nowhere near statistical significance, thus studies with such "confidence" usually don't get published unless it's a large study that refutes previous studies that appeared more confident...
 
Careyp74 said:
Sure, it has equal chance of affecting each group, but this would diminish the confidence level.
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How so? If each group similarly engages in riskier behaviour, then the results of the experiment should still hold I think.

Also you could check to see if the participants in the experiment did actually engage in riskier behaviour by comparing infection rates in the placebo group to infection rates in the general population.
 
Lothian said:
The article suggests that no one was injected with HIV!

This study showed that 9 per 1000 people on the placebo got HIV compared to 6.5 per 1000 on the drug. 16,000 took part but only 125 caught HIV. I am no expert but wonder about the confidence level when so few went on to get the disease. There are no details in the article as to how many of each group were in high HIV risk categories.
While any improvement in preventing HIV is welcome we need to be sure that this drug does have the supposed effect.
Click to expand...

The study did say the difference could be due to chance. They will try to replicate the results now. :)

McHrozni
 
Lothian said:
0.024% less chance of getting HIV in the treatment group.
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No, 31% less chance of getting HIV.

Can we say as result of this that we are 100% certain that this treatment lowers the risk
Click to expand...

Of course not. A single un-replicated study can never give 100% certainty, even when the results are far more conclusive. But it's certainly a good sign.
 
Cuddles said:
No, 31% less chance of getting HIV.
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My choice of percentage was quite deliberate. I have just finished rereading Ben Goldacre’s ‘Bad science’ book. He suggests that comparative percentages can be misleading and it is far better to express them in terms of absolute risk.

Of course not. A single un-replicated study can never give 100% certainty, even when the results are far more conclusive. But it's certainly a good sign.
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Thanks, I realise that, and I realise that my 50% example was just as unrealistic. I was hoping someone would know how to work out the confidence from the numbers in the article.
 
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Might vaccination perhaps encourage risky sexual behaviour? Is there a "moral hazard" to rolling our this type of treatment, particularly as it's only 1/3rd effective?
 
Cuddles said:
No, 31% less chance of getting HIV.



Of course not. A single un-replicated study can never give 100% certainty, even when the results are far more conclusive. But it's certainly a good sign.
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No study, however replicated, can give 100% certainty.
 
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