Medical Science Question

[twentysix by twentyfive]

I've been pondering the following. I'll try to keep things general and suppose an ideal type situation to attempt to get my question across clearly. (Tough ask in my case )

Let's suppose an individual is vaccinated (topical at the moment). Let's assume that the vaccine is safe with, say, a 1 in 1 million (or whatever) chance of an unpleasant and definitely unwanted side effect. Let's further suppose that the individual in question is very unlucky and is that 1 in 1 million and has the side effect. Let's now suppose that the protective effect of the vaccine declines to zero (so that the population as a whole and our individual are set to the same biological start points as before) so that another vaccination is required (in this case the same one as before). My question is - does our previously unlucky individual have the 1 in 1 million risk of that side effect this second time around or is the risk to the individual 100%? ie is the individual always the unlucky one in the population due to some inherent individual biological quirk?

I've tried to exclude other external influences which would certainly be present in a real world scenario to get at the essence of the pondering.

Just wondering. It would be interesting to hear from a medical scientist/doctor/biologist/vaccine expert........ Any of those on here?

 

[midlife]

If the chance of side effect was purely random it's like throwing a dice. The past has no bearing on what the next number will be.

 

[slowmotion]

If (1) the protective effect of the vaccine has declined to zero and (2) it's the same disease/variant as before, he/she has exactly the same chance of getting side effects the second time around.

Edit @midlife beat me to it.

 

[twentysix by twentyfive]

If the chance of side effect was purely random it's like throwing a dice. The past has no bearing on what the next number will be.

I think I'm asking if there is cause and effect. I agree that if it's just random then the vaccinated individual would have that much lower population risk.

 

[slowmotion]

I think I'm asking if there is cause and effect. I agree that if it's just random then the vaccinated individual would have that much lower population risk.

If the protective effect of the vaccine actually has declined to zero, it's like it was never taken. Therefore the probability of getting an adverse reaction the second time around is the same as with the first jab.

 

[twentysix by twentyfive]

If the protective effect of the vaccine actually has declined to zero, it's like it was never taken. Therefore the probability of getting an adverse reaction the second time around is the same as with the first jab.

Yes that's why I supposed it to decline to zero. So back to the start point. But we now have new information for the second cycle.

To our mythical individual that would be 100% then? While the rest of the million will be fine?

 

[C R]

I think I'm asking if there is cause and effect. I agree that if it's just random then the vaccinated individual would have that much lower population risk.

I suppose the rub is why they suffered the side effect in the first place. If there's an underlying reason why they suffered the side effect, whether the reason is known or unknown, then their individual probability may be much higher than the general population probability.

 

[Ian H]

If we're talking about a real-life Covid vaccine, it's worth pointing out that millions of women take a drug which is much more risky: the Pill.

 

[slowmotion]

To our mythical individual that would be 100% then? While the rest of the million will be fine?

No. It would be one in a million or whatever it was before. If I blow my brains out the first time I play Russian Roulette, it doesn't mean I'll do so second time around.


......hang about.......I'll have to ponder that further.......

 

[twentysix by twentyfive]

I suppose the rub is why they suffered the side effect in the first place. If there's an underlying reason why they suffered the side effect, whether known or unknown, then their individual probability may be much higher than the general population probability.

Good. That's what I'm driving at I think. Are these side effects truly random at the individual level?

 

[twentysix by twentyfive]

No. It would be one in a million or whatever it was before. If I blow my brains out the first time I play Russian Roulette, it doesn't mean I'll do so second time around.


......hang about.......I'll have to ponder that further.......

I edited my response to include prior knowledge. In the Russian roulette example that might mean we know where the bullet is..............

 

[C R]

If we're talking about a real-life Covid vaccine, it's worth pointing out that millions of women take a drug which is much more risky: the Pill.

Yes, but women with known coagulation problems are advised not to take it. That's the issue. In terms of risk analysis, though, are the side effects of the vaccine, if suffered, worse than the effects of the disease, if caught, and also, what are the relative probabilities of each of them happening.

 

[twentysix by twentyfive]

If we're talking about a real-life Covid vaccine, it's worth pointing out that millions of women take a drug which is much more risky: the Pill.

I'm really attempting to get at the meaning of the statistics for the unlucky. Do the unlucky women on the pill continue to be so as they progress with the tablet might be a question.

 

[C R]

Good. That's what I'm driving at I think. Are these side effects truly random at the individual level?

No they are not, that's why people with known problems might be advised against getting vaccinated.

 

[Fab Foodie]

Is the answer: B?