[evan_au]

we would need more than 125% of the population vaccinated.
And that's without excluding children and refuseniks.

The existing vaccines are all designed to be effective against the original (Wuhan) variant*
- They are not so effective at preventing infection and transmission of the new variants, but they are still very effective at reducing the death rate, transmission and probably the incidence of long COVID (compared to unvaccinated people) - so that's a win!
- Reducing circulation in the worldwide community is essential to reducing the number of new variants popping up
- While the vaccine makers work on their vaccine 2.0 that will deal with the newer variants.

If, with vaccination, we can make COVID-19 like the common cold, we won't need to vaccinate every year, as everyone will catch it as a child, before they get old enough to die from it

If, with vaccination, we can make COVID-19 like the flu, we can leave it to susceptible older individuals to get an annual booster, but the younger people may decide to "tough it out", on the basis that they will probably survive it.

*PS: Why isn't the original (Wuhan) variant called "Alpha", instead of the Kent variant?
- Maybe we should call it "ground zero"?

[Bored chemist]

*PS: Why isn't the original (Wuhan) variant called "Alpha", instead of the Kent variant?

Because it's the first change that gets called alpha.

[alancalverd]

From Wiki, covid R0 is 2.4 - 3.4,

Surely R is the average number of people infected by one carrier. It isn't strictly a property of the disease but of the behavior of the population, which is why quarantine works: if no carrier makes contact with anyone one else, R = 0.

[vhfpmr (OP)]

Surely R is the average number of people infected by one carrier.

R is the average number of people infected by one carrier, R₀ is the average number of people infected by one carrier in the absence of social distancing measures.

[vhfpmr (OP)]

So we do achieve herd immunity to one year's version

HIT for flu is 17% - 29%, if there were that many getting it each year I would have expected to have had the flu at least once myself. I'm 62, and never had (symptomatic) flu yet. I don't know how common that is, perhaps I'm just immune.

[vhfpmr (OP)]

While the vaccine makers work on their vaccine 2.0 that will deal with the newer variants.

I suppose what I'm driving at is can they roll out new vaccines faster than the virus rolls out new mutants? Evolution means that faster mutating variants will prevail.

[alancalverd]

R is the average number of people infected by one carrier, R₀ is the average number of people infected by one carrier in the absence of social distancing measures.

So it is entirely dependent on where you live and how you travel. The probability of a nomadic hunter infecting anyone other than his immediate family is negligible, whereas the sort of people who cram into tube trains twice a day and spend their evenings in sweaty clubs can infect dozens.

can they roll out new vaccines faster than the virus rolls out new mutants?

No. You can't hit a target without seeing it first! You might strike lucky with something that turns out to be as effective against Y as it was against its design target X, or you might come up with a "nuclear option" that alerts the body to every kind of invader without actually precipitating autoimmunity, but the chances of either are small. The enemy is mutating with every generation and in principle it only takes one survivor  to kick off a whole new swarm of invaders and evaders.Positive prevention (quarantine) is the only guaranteed effective response.

[evan_au]

can they roll out new vaccines faster than the virus rolls out new mutants?

No, but they have a fairly effective system in place for influenza:
- A worldwide network monitoring for new flu strains*
- A tracking system which records the genetics & spread of new strains (which was reused for COVID tracking)
- A team of experts who predict what are likely to be the common variants in 6 months time (for the opposite hemisphere about to enter winter)
- A vaccine platform (chicken eggs) which can quickly pivot to manufacturing vaccines for these new variants
- A manufacturing and delivery system that can get vaccines into the arms of susceptible people before winter gets underway.

It's a fairly well-oiled machine; it's not always right, but at around 75% effectiveness, that reduces mortality by more than 75%.
- And especially if they insist on visitors to aged care homes being vaccinated (as happened around here, this year)

*I expect that the team monitoring for flu-like symptoms in Wuhan were alerted to an outbreak of a respiratory illness early in 2020. But as soon as they discovered that it wasn't flu, they decided it was just SEP (Someone Else's Problem) and ignored it.

See: https://en.wikipedia.org/wiki/Influenza_vaccine#Annual_reformulation

[vhfpmr (OP)]

R is the average number of people infected by one carrier, R₀ is the average number of people infected by one carrier in the absence of social distancing measures.

So it is entirely dependent on where you live and how you travel. The probability of a nomadic hunter infecting anyone other than his immediate family is negligible, whereas the sort of people who cram into tube trains twice a day and spend their evenings in sweaty clubs can infect dozens.

It is, but that's not the point. The values of Ro I was quoting from Wikipedia are presumably population averages, and so are the calculations you need to do if you want to vaccinate a population. Nobody cares whether Mrs Jones infects Fred Bloggs (until it comes down to contact tracing), what's of interest is how many new infections you get on average from each 1000 infected. Since the majority of the population live in densely populated areas, the infection rate in those areas is going to be of more relevance and interest than the rate out in the sticks.

can they roll out new vaccines faster than the virus rolls out new mutants?

No. You can't hit a target without seeing it first! You might strike lucky with something that turns out to be as effective against Y as it was against its design target X, or you might come up with a "nuclear option" that alerts the body to every kind of invader without actually precipitating autoimmunity, but the chances of either are small. The enemy is mutating with every generation and in principle it only takes one survivor  to kick off a whole new swarm of invaders and evaders.Positive prevention (quarantine) is the only guaranteed effective response.

That's not what I was getting at, it's obvious you can't prevent a disease that hasn't arisen yet, what I was wondering is if we'll get to a stage where we can't finish vaccinating everyone against one variant before the next arrives. Producing and administering a vaccine is going to take a year or so just in the first world, let alone the third world, and in that time, numerous mutants have already arisen, any one of which could have been resistant.

[vhfpmr (OP)]

they have a fairly effective system in place for influenza

But they were only vaccinating a tiny sector of the population for flu. At 62, I wasn't eligible for the flu vaccine until they lowered the age limit to 50 this year. Covid requires everybody to be done, and that's on top of doing the flu as well. There was a piece on the Radio 4 Today programme this morning covering the increasing unrest among GPs about the impending workload.

[alancalverd]

what's of interest is how many new infections you get on average from each 1000 infected. Since the majority of the population live in densely populated areas, the infection rate in those areas is going to be of more relevance and interest than the rate out in the sticks.

And as we have seen repeatedly, R in any area is not simply a function of population density or infectivity, neither of which has changed in the UK until the delta variant arrived, but of human behavior. Strict quarantine prevents  transmission, vaccination sometimes prevents infection of the recipients of what is transmitted. Quarantine can be applied rapidly and universally if you have a competent government, and is 100% effective in a few weeks, whereas vaccination  requires development, testing, production,distribution and delivery, takes 18 months to cover 50% of the population, has all sorts of side effects and doesn't always work.

The problem is that we have a corrupt and incompetent government, so we have to put up with excess deaths, long COVID, and a permanently damaged economy, instead of a month's national holiday and effective border controls

[vhfpmr (OP)]

None of this is of any relevance to what I'm arguing. If you want a vaccine that will enable you to end quarantine and return to normal behaviour, then you need to do vaccine calculations using the R value that relates to normal behaviour, and not that which relates to quarantine conditions. We've already shown that we can get R below one using quarantine alone, the open question is whether can we get R below one using the vaccine alone.

[Bored chemist]

It's relatively easy to find out how well a vaccine prevents death.
You take a big group, vaccinate half of them, and then count the deaths in each group.
It's more difficult to measure the prevention of infection where many infections are asymptomatic.
You need to regularly re-test all the people in your survey.

It harder, but it's possible.

But it's difficult to measure the effectiveness of a vaccine in terms of how much it reduces spread, because, in general, we simply don't know who the virus was spread to and from.


So the only thing you can do is vaccinate essentially the whole population and see what happens to the measured value of R (and make the laughable assumption that nothing else has changed).

So, yes, it would be great to know if the vaccine can end the pandemic,
But the only way to find out is to vaccinate the population (or some acceptable subset) and see if it works.

[alancalverd]

you need to do vaccine calculations using the R value that relates to normal behaviour,

Assume that reinfection is not possible, and that normal behavior depends on their being a negligible probability of being infected even if you take no special precautions.

If R < 1 then normality will prevail when a sufficient number have been infected, whether or not you vaccinate anyone.

If R > 1 you will reach that equilibrium quicker and with more casualties.

[vhfpmr (OP)]

If R < 1 then normality will prevail when a sufficient number have been infected, whether or not you vaccinate anyone

If you leave people to get infected without a vaccine, a lot more will die.

[alancalverd]

Only about 4%, and mostly the elderly and infirm, as with any herd. The problem with COVID is that 20% of those infected require hospital treatment and half of those suffer longterm disability: this is more serous than death for the herd.