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One-jab efficacy questions

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Chris152

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On 18th March, Johnson said that 'a single dose of either Pfizer or AstraZeneca vaccine provides a 60 percent prevention from Covid-19 [he didn't specify which variant, not sure if that makes a difference] and that it reduces hospitalisation by 80 percent, as well as death by 85 percent'.
What did the PM say in his speech tonight, Thursday, March 18?
Two questions:
1. Does that mean if you've had the jab but still contract the disease, you're only 20% less likely to end up in hospital / 25% less likely to die than if you'd not had the vaccine?
2. If we're 60% protected against contracting the virus, but the virus is now 50-70% more contagious than this time last year, aren't we back where we were last April in terms of likely spread? R seems to have risen to around 1 in England at the top end of the estimate, now.
Thanks if you can clarify any of this. Oh, and I don't want to know it's unimportant etc, just clarification on the stats.
Confused of Cardiff.
 
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MARK.B.

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The first question i would think, is you are 80% less likely to end up in hospital and 75% less likely to die if you do go to hospital.
As for number 2 i don't have a answer, a lot of unknown's still to be found as the Virus is still mutating. :)
 

Chris152

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I think that was my initial understanding of what he said (a NHS spokeswoman had made a real mess of stating the same stats a few days before, so I guess he was trying to clarify) but on reflection, from the govt's perspective, it'd be quite reasonable to state that the vaccine provides 80% protection against hospitalisation/ 85% against death from the position of a non-infected, single-jabbed person - as those are the figures they're focused on. If so, then the vaccine only provides 20-25% further protection against hospitalisation/ death if you contract the disease?
 

powertools

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All I can say is that I think that we are all confused but the main stats show that since to vax roll out started all the bad news seems to have gone down to a low level.
I am happy to say that today I have had my second jab and I accept that I could still get covid but assume that it would not be as bad but I am still going to be cautious how I lead my life.
 

Terry - Somerset

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As I read the numbers:
  • with one jab you are 60% less likely to catch the virus
  • if you do get the virus you are 80% less likely to be hospitalised
  • if hospitalised you are 85% less likely to die
So compared to the unvaccinated my chance of dying from Covid is:

40% x 20% x 15% = 1.2%

Perhaps I'm just an optimist. It would be nice to know what the figure so casually bandied actually mean!
 

RobinBHM

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If we're 60% protected against contracting the virus, but the virus is now 50-70% more contagious than this time last year, aren't we back where we were last April in terms of likely spread? R seems to have risen to around 1 in England at the top end of the estimate, now.
its an interesting point, I would say the reality is: we simply dont know, early date feedback indicates the vaccine reduces transmission, but thats only small studies.

Im not sure your maths would add up as Im not sure the 2 would cancel each other out.
 

RobinBHM

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If so, then the vaccine only provides 20-25% further protection against hospitalisation/ death if you contract the disease?
I think it means that you have 80% further protection against hospitalisation if you contract covid.

I know somebody that caught covid over 3 weeks after being vaccinated -she was quite ill for 2 weeks and still recovering after 4 weeks. I know statistically it means nothing but given she is mid 70's my guess is its possible she may have been hospitalised from it. (its rather sad really, her husband got ill not from covid, got covid in hospital, came home and gave it to his wife. He got readmitted to hospital and then died (not from covid).
 

Chris152

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Thanks fellas. I've done a fair bit of searching on the net but can't find the answers. Odd that we seem to be left guessing what the figures mean, different readings make a big difference to where we stand I think.
 

TRITON

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STOP IT, Just STOP IT.
I've been trying to avoid looking at threads such as these :LOL: It's 8:34 now and I've an appointment today at 9:40 to get the vaccine.
 

Ozi

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As I read the numbers:
  • with one jab you are 60% less likely to catch the virus
  • if you do get the virus you are 80% less likely to be hospitalised
  • if hospitalised you are 85% less likely to die
So compared to the unvaccinated my chance of dying from Covid is:

40% x 20% x 15% = 1.2%

Perhaps I'm just an optimist. It would be nice to know what the figure so casually bandied actually mean!
These are population stats so don't multiply quite like that basically if you compare two groups one vaccinated one not then the treated group

will have
60% less infections
80% less hospitalized
85% less deaths

so if we had a new infection rate of 6000 per day that would become 2400 etc.


presumably it also means that of those infected a higher proportion will be symptom less. This is why all the children that are back at school are being tested and the tests logged nationally so that the effect of each step of reducing lock down can be measured. It's also why vaccinated people still need to be cautious as we could still be spreading it. A problem is that it's difficult to isolate effects within a population and this may be seasional or if not directly then effected by seasonal events (at the start we were told that if you got flue and covid together you were 8 times more likely to die. What happens in the next flue season will really tell us how successful this has been, but probably the most important thing is that as many people on earth as possible get the vacine, it's in the self interest of rich nations to reduce the sorce of potential mutation before something comes along to put us back to square one.
 

Chris152

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These are population stats so don't multiply quite like that basically if you compare two groups one vaccinated one not then the treated group
will have
60% less infections
80% less hospitalized
85% less deaths
Makes sense, but less optimistic than it originally sounded to my ears! But obvs still worth getting the shot, Triton - be brave :)
 

Woody2Shoes

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Makes sense, but less optimistic than it originally sounded to my ears! But obvs still worth getting the shot, Triton - be brave :)
The other thing worth noting is that after a second ("booster") jab the figures improve further by a reasonably encouraging margin. As suggested upthread, the biggest risk is from a new variant - developing where the infection rate is highest, most likely - evolving to evade the current set of vaccines. We know that the vaccines can be 'tweaked' within months, now that their basic function has been proven. The human race is not out of the woods yet - probably.
 

Terry - Somerset

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Policy seems to be increasingly driven by the possibility that the Covid virus may mutate, evade current vaccines, transmit more freely, or have more severe consequences.

I am unclear whether this is a real threat, or fearmongering to keep the proletariat in line.

All viruses mutate - flu, chicken pox, measles, mumps, AIDS, etc. The risk of mutation must increase with numbers infected worldwide yet we just accept this risk.

What makes Covid different.
 

Ozi

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Policy seems to be increasingly driven by the possibility that the Covid virus may mutate, evade current vaccines, transmit more freely, or have more severe consequences.

I am unclear whether this is a real threat, or fearmongering to keep the proletariat in line.

All viruses mutate - flu, chicken pox, measles, mumps, AIDS, etc. The risk of mutation must increase with numbers infected worldwide yet we just accept this risk.

What makes Covid different.
The number of people it's killed and the speed of mutation.

Chicken pox, measles and mumps mutate relatively slowly and the bodies immune response persists so if you get then once and fight off the infection you are likely protected for life from any new variety as your body can cope with small changes. AIDS is not an airborne infection and quite difficult to catch. Flu is in many ways similar to covid and sometimes throws up a dangerous strain like Spanish flu, it evolves quickly so we need new vaccines each year, but we have been living with flu a long time, it's nasty but most people can cope with it, the annual death rate doesn't overwhelm our health service although in a bad year it can get close.

With luck covid will become like flu something most people can live with and our lives can get back to normal. The fight does seem to be going our way but we should learn some lessons.

This bits politics and just my opinion

we need to stop letting our votes be bought with tax cuts, I remember income tax at 30%, I think most people here probably do, it's the fairest tax going although any tax will be unfair on someone. We need to rebuild the NHS and take some urgent actions to clean this place up.

We need to stop treating elections like reality TV and vote for people who can show they have achieved something, why is MP the only job you can apply for without a CV.

We need to stop being NIMBYs. People need houses and old environmentally unsound houses need to be replaced, that means building in your area, it means richer areas subsidizing poorer areas.


Sorry, climbs off soap box again
 

Rorschach

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Be interesting to see how recent news affects take up among the young.
 

Woody2Shoes

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Policy seems to be increasingly driven by the possibility that the Covid virus may mutate, evade current vaccines, transmit more freely, or have more severe consequences.

I am unclear whether this is a real threat, or fearmongering to keep the proletariat in line.

All viruses mutate - flu, chicken pox, measles, mumps, AIDS, etc. The risk of mutation must increase with numbers infected worldwide yet we just accept this risk.

What makes Covid different.
The truth is, nobody knows - but 'common' sense suggests it is right to be cautious. Covid-19 has characteristics which make it fairly unusual (in our lifetimes at least):
1) There was no natural immunity in the human population anywhere on the planet, as far we know, before about 16-18 months ago.
2) It has a characteristic 'spike' protein which most/all vaccines seem to be relying on as the 'marker' for the virus. The 'signature' of this spike can vary with mutations - a tiny random mutation might stop the vaccines working (or at least badly reduce their chances of being effective) while allowing the virus to have similar effects on the human body. The more infections, the more mutations, until we can vaccinate everybody we have no choice but to accept the associated risks.
3) It's becoming increasingly clear that there is a post-covid-syndrome/long covid which is affecting a lot of people - often more likely to be younger and female more often than those who simply get killed by it. It's a pernicious, highly transmissible virus however you look at it.
 

George_N

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Policy seems to be increasingly driven by the possibility that the Covid virus may mutate, evade current vaccines, transmit more freely, or have more severe consequences.

I am unclear whether this is a real threat, or fearmongering to keep the proletariat in line.

All viruses mutate - flu, chicken pox, measles, mumps, AIDS, etc. The risk of mutation must increase with numbers infected worldwide yet we just accept this risk.

What makes Covid different.
“All viruses mutate” but some mutate much more rapidly than others. Chicken pox, measles and mumps mutate much more slowly than flu or coronaviruses and are well controlled by vaccination programs. Coronavirus appears to be much more infectious than flu, given that it has continued to spread despite lockdown, mask use and social distancing, whereas flu cases have been the lowest ever recorded.
You are right that the bigger the pool of infected individuals, the greater opportunity there is for mutant strains of the virus to arise. Which just reinforces the need to get everyone vaccinated ASAP. To get proper protection we need BOTH shots, the first shot only gives partial protection that will wane relatively quickly (a few months).
 

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