discussion on how efficacy and effectiveness rates are determined

[purslaine]

https://www.hidionline.com/hidi/Documents/Vaccine_Epidemiology.pdf

I thought this was a really interesting discussion on how efficacy and effectiveness rates are determined.

[Cynthia Mosher]

Thanks for sharing. 

[Taximom5]

That's fascinating--because it's TOTALLY different from what most people believe.

Most people think that a vaccine that is 58% effective will prevent the disease in 58% of the people who receive the vaccine.

In reality, 58% fewer vaccinated people will get the disease compared with unvaccinated people--and in many cases, like influenza, unvaccinated people who wash their hands, get proper nutrition and rest, etc., are unlikely to get the disease in the first place.

Great article--thanks for posting!

[purslaine]

Originally Posted by Taximom5 

That's fascinating--because it's TOTALLY different from what most people believe.

Most people think that a vaccine that is 58% effective will prevent the disease in 58% of the people who receive the vaccine.

Great article--thanks for posting!

That is what I believed until about a week ago, lol.

The article was a real eye opener.

[prosciencemum]

That is a good thing to share. It's important to check we understand the statistics. 

Of course if you think about it effectiveness has to be something you can measure, and a VPD can only be caught if you're exposed to the bacteria/virus which causes it. So it would be impossible to measure which fraction of people vaccinated are protected from the disease - the only way to do that would be to deliberately expose them to the diseases after they were vaccinated. And that kind of testing is clearly unethical. 

So all they can do is take a sample of vaccinated and unvaccinated people who live in a similar environment (I assume they do their best to control for things like socio-economic group, geographic location etc) and see how the rates of the disease differ in the vaccinated and unvaccinated populations.

Ultimately if a vaccination can become widespread enough that the disease dies off (like it did for small pox) and then the vaccination is no longer needed that would be the best results. I realise that is probably a pipe dream for many of the diseases today (which if I understand the argument seem to mutate more than small pox did), but it would still be fantastic. :)