AstraZeneca currently thought to cut transmission by 50%

[salmonskinjerky]

I can't link to the article because its part of a Guardian liveblog, so I'll paste it here;

Vaccines do not completely stop transmission, JCVI member says
Covid-19 vaccines do not completely prevent transmission, Prof Anthony Harnden, deputy chair of the Joint Committee on Vaccination and Immunisation (JCVI) has said.

He told BBC Breakfast on Sunday that while they appear to reduce transmission by about 50%, vaccinated people can still get the virus and spread it to others.

He added:

There’s some good evidence now from Public Health England and from the Oxford/AstraZeneca trials that the vaccines do prevent transmission.But they don’t completely prevent transmission. The figures are still being calculated but it’s in the order of 50%.

So, there will be some reduction in transmission, no doubt at all, but it’s still possible, even though you’ve been vaccinated, to get infected, have no symptoms and transmit it to others. That’s why it’s important that all those who get vaccinated still stick to the rules.

So long as no-one is getting seriously ill then great. It’s here to stay. Not seeing family & friends, destroying businesses is not. If everyone is vaccinated, none of us will need the NHS. And that’s the point.

@FourTeaFallOut

No it's bullshit. Is it 50% transmission among the entire vaccinated cohort or 50% transmission of those who get coronavirus despite a vaccine? For instance, is that clear yet?

I would've thought that in this context the simpler and more intuitional meaning (ie the first one) would have been meant? Otherwise its pretty shocking messaging.

I mean, that's not my intuition and I'm not being deliberately awkward to forge the discussion, my gut feel was that it must be the latter. I mean, how could it be that the capacity to contract and transmit is only reduced to 50%? In that case, how many are contracting the virus and not transmitting it?

Do we think that this will stop people trotting out “actually the vaccines only stop you having symptoms, they don’t stop you passing it on” on every sodding vaccine thread? Do we hell.

Yeah, it's annoying, isn't it.

Am I the only person who is waiting until it's legal for me to visit my mother (who lives two hours' drive away and in Wales to boot), rather than doing it anyway because we've both had a first jab?

A lot of wrong information on this thread - and once again the anti-vaxxers are out and about I see.

Vaccines don't stop ANYONE contracting a virus. The adaptive immune system only kicks into action AFTER you've been infected. It's the same if your immunity is "naturally" acquired. Once the virus starts to multiply in your body, your immune system kicks in and starts eradicating it. If your immunity is excellent, then this occurs before symptoms can appear.

With covid, we have long suspected that people are transmitting the virus MOSTLY before symptoms show, so for a vaccine to STOP transmission as well as symptomatic disease, your immune system would have to act even quicker - hence the lower %'s.

There are two headline figures bandied around - the reduction in risk of serious illness/death which is typically between 90 and 100% depending on which vaccine/study you look at, and the reduction in risk of symptoms developing which is 60-75% for AZ and from recall 80-95% for Pfizer.

And for the trolls scoffing at 50% - it's an enormous result. It HALVES R! And it's important to note it's going to be largely based on evidence from those with the weakest response to the vaccine since they were the first groups to be innoculated.

A corresponding and more complete study in progress in Israel is talking about 89%+.

www.reuters.com/article/health-coronavirus-israel-vaccine-int-idUSKBN2AJ08J

If everyone is vaccinated, none of us will need the NHS

Sometimes I wonder how the human race managed to survive this long without being overtaken by a smarter group such as cabbages.

50% is pretty damn good. That, along with its protection against serious symptoms should (along with the other vaccines) get this thing to a point where we can live our lives, surely.
We cannot aim for zero risk and I'm tired of people who seem to think we can.

@FourTeaFallOut

I mean, that's not my intuition and I'm not being deliberately awkward to forge the discussion, my gut feel was that it must be the latter. I mean, how could it be that the capacity to contract and transmit is only reduced to 50%? In that case, how many are contracting the virus and not transmitting it?

With the caveat that I’m a mathematician not a medic so my terminology may be flaky, my understanding is that vaccines may in some cases act to enable you to fight off the virus very effectively, so you still have it, you may still test positive, but you have no noticeable symptoms. You’d still be potentially infectious but with a lower viral load you’d be less likely to pass it on.

That’s why you’d get a lower figure for “prevents infection and transmission” than for “prevents severe illness”. All the experiments which have attempted to put a number on this have shown that vaccines do work to prevent infection, but they don’t work quite as well as they do to prevent severe illness.

www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fcoronavirus%2F2019-ncov%2Fmore%2Ffully-vaccinated-people.html
This CDC article is good and refers to some very optimistic studies on Pfizer/Moderna, but there have been some others which don’t show quite such positive results. 50% does seem at the conservative end.

@FourTeaFallOut

No it's bullshit. Is it 50% transmission among the entire vaccinated cohort or 50% transmission of those who get coronavirus despite a vaccine? For instance, is that clear yet?

50% of the people who have the vaccine will still be able to transmit the virus.

I’m not sure how an individual would have 50% transmission tbh.

To be quite honest, it's nice to be having the vaccine to protect me.
So far in this pandemic everything I've done is to protect others

It protects 100% against dying and being hospitalised that is good enough for me and others when vaccinated

It's good but not 100% surely? It may have had 100% in trials but that's not the same

I agree SPB, there were zero cases of death or serious illness in the vaccinated sample but there weren’t large numbers of deaths or serious illness in the placebo group. It definitely works, it’s a triumph of medical science, but the error bars around that 100% figure have got to be pretty sizeable.

80% -100% would rather that to the alternative

www.bmj.com/content/372/bmj.n793

I'm just not sure how it could be as little as 50% when the bmj are reporting research that has the reduction in both symptomatic and asymptomatic infection at 67% with just a single dose?

And as for Pfizer, data in Israel suggests that asymptomatic infection is reduced by up to 90% following both doses - albeit at a much shorter period than we are administering.

So how could the reduction of onward transmission ever be as little as 50%? This is why I am questioning some of the assumptions around the statement.

Notrub please can you go back through my posts and simply replace the word contracted with whichever word you would prefer to classify those who neither get sick nor who go on to infect others following exposure so as to make the exposure entirely redundant and work from the assumption that the language around all this is fairly slippy for a regular person rather than assume I'm posting in bad faith as an anti vaxxer, please?

Because you could still be carrying/transmitting the virus even if does not make you ill.

@FourTeaFallOut That BMJ article appears to relate to the AZ US study, which the US disputed and they then adjusted...

But it also seems to only refer to symptomatic CV?

On the news just now, they said that most vaccines appear to offer an 80% reduction in symptomatic cases, but that this new data suggests that you still have a 50% chance of being able to transmit the virus to others. So your vaccine is pretty effective at stopping you from becoming seriously unwell, and most are very good at stopping you being hospitalised, but they only halve your chances of transmitting it.

Which I suppose means more asymptomatic transmission?

But the news are not perfect in their reporting, and none of this seems easy to understand.

@canigooutyet

It doesn't matter if you have all been vaccinated, you still have to follow the guidelines. This has been made clear since the beginning that masks and sd'ing will still be required.

You are still advised to follow the guidelines... masks and social distancing are still advised. There are guidelines and there are laws. We must follow the laws, we should follow the guidance. But you don't have to.

On a completely separate theme, if "vaccine passports" do become a thing for booking/entering venues, do you think there will become a market for fake vaccine passports ..?(unthinking of the fake IDs for getting into pubs/clubs when I was young!)

But asymptomatic infection is far less likely to transmit than symptomatic infection.

It has been revised down to 17% of transmission - before you even introduce a vaccine.

www.bmj.com/content/371/bmj.m4851

www.bmj.com/content/372/bmj.n326

Sorry TakeYourFinalposition, I have too many tabs open and linked to the wrong article, it's this one ^^

"However, the researchers found that after a single dose of vaccine, overall polymerase chain reaction test positive cases of covid-19 (both symptomatic and asymptomatic) fell by 67%, raising hopes that it may have a substantial impact on transmission by reducing the number of infected people in the population"

You are still advised to follow the guidelines... masks and social distancing are still advised. There are guidelines and there are laws. We must follow the laws, we should follow the guidance. But you don't have to.

I think that’s a helpful distinction, @ChocOrange1. The trouble has been differentiating between law and guidelines - even the police have had trouble with that.

At the moment, it is against the law for me to go and visit my mum in Wales. Time will come when it’s legal, but only out of doors. When we reach the point that it’s legal for up to six to meet indoors, there will probably still be advice about 2m distance and wearing a mask. But given that by the time we can meet indoors we will both be post-2nd vaccine, I’m buggered if I’m going to obey that guidance.

@HolmeH

So long as no-one is getting seriously ill then great. It’s here to stay. Not seeing family & friends, destroying businesses is not. If everyone is vaccinated, none of us will need the NHS. And that’s the point.

This