Johns Hopkins Medical Centre - World Coronavirus infection Map by Country.

[Macca]

Sorry to disagree, but I don't think the maths works for herd immunity - or at least not yet. In the long term it might, but on the one hand we perhaps don't want too many people to get it, and if we could get the numbers low enough it might go away, but on the other hand for herd immunity we need more people to get it - more even than the current rate of infection would suggest.!

It's a long-term strategy, balancing the infection rate against hospital admissions. I've seen estimates that say up to 40% of the population have already had the virus although many have shown little or no symptoms. As antibody testing increases that estimate will become more accurate. As time goes on the percentage will increase to herd immunity levels.

The trick is to achieve herd immunity without overwhelming the health care system. So it will take time. There's currently no evidence that you can catch it more than once.

[Macca]

No. Herd immunity is frequently misunderstood. It is typically referenced when determining the proportion of a susceptible population that needs to be immunised in order to provide effective control of an infectious disease such as measles, TB, and polio. The reasoning is that even if the whole population is not immunised, the pool of susceptible uninfected individuals is sufficiently low to prevent widespread infection. The estimates for herd immunity to be effective vary but at the very minimum, it is around 70% of the population. If herd immunity is to be achieved in the UK this would require over 40m individuals to be infected, with the huge burden of mortality and morbidity that would entail. Furthermore, if COVID 19 is like influenza, and mutates slightly each year, herd immunity will be rapidly lost and the whole population (or a large percentage of the population) will require re-immunisation each year.

The reason that case mortality rates have fallen faster than the rate of new infections is that better treatments have been developed. However, any gains from reduced case mortality rates may well be offset by rapidly rising infection rates which is what we are currently experiencing. Anybody who understands exponential growth will appreciate the consequences of the reproduction rate rising appreciably above unity.

I think we all understand what herd immunity is, it isn't a difficult concept to grasp. I think we all understand what exponential growth is too. It's possible to reach herd immunity without exponential growth, it is just a question of time.

People more susceptible to the virus need to remain isolating and take extra precautions. Ultimately they will benefit the most from herd immunity. You don't want the R value to fall too low (unless it is a result of reaching herd immunity) otherwise you will never reach herd immunity. Likewise you don't want it going too high as it may overwhelm health services. So it is being managed with local lockdowns, social distancing, mask wearing etc. Those things alone will never eradicate the virus. That seems to be the bit that some people don't get.

[Marco]

It's a long-term strategy, balancing the infection rate against hospital admissions. I've seen estimates that say up to 40% of the population have already had the virus although many have shown little or no symptoms. As antibody testing increases that estimate will become more accurate. As time goes on the percentage will increase to herd immunity levels.

The trick is to achieve herd immunity without overwhelming the health care system. So it will take time.

Indeed.

I think we all understand what herd immunity is, it isn't a difficult concept to grasp. I think we all understand what exponential growth is too. It's possible to reach herd immunity without exponential growth, it is just a question of time.

Absolutely. Ultimately, allowing nature to take its course [in tandem with controlling the spread of the virus as much as possible, taking all reasonable and necessary precautions], is the ONLY real way of getting through this.

Marco.

[Marco]

Furthermore, if COVID 19 is like influenza, and mutates slightly each year, herd immunity will be rapidly lost and the whole population (or a large percentage of the population) will require re-immunisation each year.

Same would apply with any vaccine, which even if safe, would never be 100% effective over a long period of time. Therefore, as I've said (also Macca), ultimately herd immunity , however long it takes, is the only real solution, and with that, Covid-19 will *eventually* go the way of Swine Flu or SARS... Until the next strain of corornavirus comes along!

Yes, with the way we're living now, I believe that these types of outbreaks will become more commonplace in the years to come.

Marco.

[Sherwood]

To repeat the point, herd immunity requires either an effective one time immunisation (as we have for TB, polio etc), or a long term immunity to reinfection once infected. Neither of these conditions are met or certain as yet.

Of course we need the reproduction rate to be low (i.e. below unity) because herd immunity is not an effective strategy for this disease. No competent public health specialist or epidemiologist would suggest otherwise.

[Macca]

Influenza is a covid virus and it seems to be forgotten that a lot of people die from that every year and have done for centuries. The swine flu of 2009 is estimated to have killed half a million people globally. Remember us having a lockdown and a big panic over that? No, neither do I. But it was declared as a pandemic by the WHO https://www.ctvnews.ca/who-declares-...ate%20severity.

[Marco]

To repeat the point, herd immunity requires either an effective one time immunisation (as we have for TB, polio etc), or a long term immunity to reinfection once infected. Neither of these conditions are met or certain as yet.

And to also reapeat: it will take TIME, but I believe it will happen.

Of course we need the reproduction rate to be low (i.e. below unity) because herd immunity is not an effective strategy for this disease. No competent public health specialist or epidemiologist would suggest otherwise.

It will be, if the right criteria is met, some of which you've outlined.

Marco.

[Marco]

Influenza is a covid virus and it seems to be forgotten that a lot of people die from that every year and have done for centuries. The swine flu of 2009 is estimated to have killed half a million people globally. Remember us having a lockdown and a big panic over that? No, neither do I. But it was declared as a pandemic by the WHO https://www.ctvnews.ca/who-declares-...ate%20severity.

A very salient point! And you have to ask yourself WHY...?? WHY all the panic this time, over something that is arguably less serious, and not before? What's the driving force behind the creation of panic this time?

Any thoughts on that?

Your point on influenza is also very relevant.

Marco.

[Macca]

To repeat the point, herd immunity requires either an effective one time immunisation (as we have for TB, polio etc), or a long term immunity to reinfection once infected. Neither of these conditions are met or certain as yet.

Of course we need the reproduction rate to be low (i.e. below unity) because herd immunity is not an effective strategy for this disease. No competent public health specialist or epidemiologist would suggest otherwise.

Not in public, no. But if they had another solution I'd imagine that they might mention that. So far, nothing. What are your grounds for stating that herd immunity is not an effective strategy?

[Macca]

A very salient point! And you have to ask yourself WHY...?? WHY all the panic this time, over something that is arguably less serious, and not before?

Any thoughts on that?

Your point on influenza is also very relevant.

Marco.

When it started nothing was known about the virus. So they erred on the side of caution. Also it did become clear quite quickly that C-19 was more contagious than 'flu virus and was more virulent in its effects on the average individual than swine flu. So there was a danger of the health system being overwhelmed which there was not with the swine flu. It is clearly more serious than swine flu.

My point was that there was a pandemic in 2009 and a lot of people died and it wasn't big news, barely news at all in fact. But as C-19 is big news joe punter gets to hear about it and then even one death from it is 'One death too many!'