We shouldn’t be too fixated on vaccine efficacy. What ultimately is important (& I suspect most of us are talking about) is vaccine effectiveness (VE).
Vaccine efficacy is % of reduction of disease in a vaccinated vs unvaccinated group in a trial.
VE is the real world impact.
V.efficacy measures individual protection in a controlled environment while VE looks at how protected is a population after vaccination. There is a whole host of factors influencing it.
And not necessarily v.efficacy is directly proportional to VE.
Focusing on only efficacy will distract us from implementing a good vaccination plan to maximise effectiveness.
Factors like administration, cold chain, coverage (which impacts herd immunity) all can greatly increase effectiveness, which is what we want.
Ideally yes, we would want a 100% efficacy vaccine and translate it to 100% effectiveness. But that wont happen in the real world.
Vaccinating 70% or more of the population with a 50% efficacy vaccine is better than vaccinating 30% of the population with a 90% efficacy vaccine.
Most of us are looking at the vaccine through a transmission lens. We want it to be ‘effective’ so we can go back to our pre-Covid lives; travel, socialise, etc.
But so far the vaccines r not designed for that. The primary endpoint is to decrease disease or death. Which it does.
Data from trials shows it can reduce disease burden, therefore reduce hospital overloading & reduce complications/death. This is a big win.
The messaging should be clear. It is not for us to travel, socialise without the usual SOPs.
But I suppose the market is ‘spoiled’ by the Pfizer, Moderna etc with their >90% numbers. I call it the Asian mother effect.
Vaccine X: I got 70%
Asian mother: 70%? Why not 90%? 100%?
😂
In a nutshell, we have to look at the various nuances of immunisation; efficacy, effectiveness, herd immunity (a thread for another day).
Some info on vaccine efficacy. We tend to make the mistake of 95% efficacy (Pfizer) being 95 out of 100 is protected from the disease while 5 out of 100 will get infected/succumb to disease.
But that’s not how vaccine efficacy works. So how did we get that 95%?
Consider these numbers. The Pfizer P3 trial had 43,661 participants.
Total was split into half, each group received the placebo or the vaccine. The placebo group had 162 symptomatic infection & the vaccine group had 8.
We then can calculate the infection risk. 0.74% vs 0.04%.
To get vaccine efficacy, first we get the risk difference between the two groups.
This means the vaccine reduces infection risk by 0.7 percentage point. But this is not efficacy.
Efficacy is dividing by original infection risk x 100%. Now u get the 95%.
Always amusing to see men (or rather boys) trying to use declining fertility of women by showing fertility rates to justify that women should marry young.
Firstly, reproduction is not the only purpose in life or partnerships/marriage.
Secondly, they are reading the data wrong.
Fertility rates (broadly) is defined as avg number of children born by a woman in her reproductive years over her lifetime. It measure a period, not the cohort’s metric.
And number of children born means u need the man as well, so the equal & opposite cohort to see is the men.
Blaming women biology for low fertility rates or high risk pregnancies in older women is lazy & ignorant.
Fertility rates drop in older women because their male partners are older too, therefore time to conception is later.