Covid-19 Endgames & Exiting Lockdowns

At this time (7th April), there is much talk of ‘peaks’ and ‘flattened curves’. There are suggestions that ‘the worst may be over’. Talk about lockdowns being relaxed or even removed.

An outbreak running from start to end is a journey. With Coivd-19 that journey may include trials worthy of a journey in a Lord of the Rings novel. To know if the worst is over, requires knowing where the rest of the journey will lead: the endgame. The endgame is the solution that will ends the outbreak.

For most countries now has become all about managing, and hopefully relaxing, lockdowns for the rest of journey to chosen endgame.

the endgamentries Knowing the destination, which with Covid-19, is determined by the strategy to reach the end of the outbreak: .

Most countries right now are at the point of deciding when and how to lift lockdowns. Know the possible endgames, and then the questions can be answered:

is the worst of the journey really over? How close to ‘the end’? And just what is that end? This post examines these questions.

The two ‘endgames’ or paths to the end of an outbreak are:

  1. reaching herd by immunity with 50% of population infected by either:
    • a) ‘let it run’: an unconstrained outbreak
    • b) containment: a constrained outbreak
  2. a cure/vaccine/global eradication after:
    • containment: a constrained outbreak

Before taking the next step on a journey, it is usually best to know the destination. Sometimes, when there are two possible destinations, there is a next step that works for both, other times it is already time to choose a direction. Either way, the destinations need to be considered.

This means, to know what to do after lockdowns, it is important to consider the possible endgames (or journey ends), and well understanding properly the current position.

The path to the end and exiting lockdowns:

  • Destinations: The Endgame Alternatives
  • Recognising if ‘the end is near’…or not
  • Lessons from history
    • 1918 and the ‘Spanish’ flu
    • Swine Flu, SARS, MERS
    • influenza, the common cold
  • The Endgames: Introduction
  • Endgame choice 1: herd immunity (with a flattened curve)
    • what is herd immunity
    • the solution to the Spanish Flu in 1918
  • Endgame choice 2: containment and wait
    1. containment
    2. wait for either of:
      • a cure and/or vaccine
      • global eradication
  • Calculating the Costs
    • Why the mortality rate from Flattening the Curve?
    • the history
    • the data: What can we trust?
    • the reality
  • The Curve is Flattening: Time to Decide
    • Check The Data
    • Review The ‘Flattening’ Trend
  • Conclusion: The problems from not making a decision.

Is the end near.. or not?

As stated in the introduction, there are two ‘endgames’:

  • Herd immunity, after 50% of the population have been infected.
  • Vaccine/ Cure or complete global eradication

No country is even close to 50% of the population having been infected, or has even reached that halfway mark. There is no cure or vaccine, and complete global eradication appears furtherest away of all!

So no, the end is not near. It does not look like anyone is even half way to the end. The only hope is that the path to end can be easier than the path to this point.

Reading The Tea Leaves: A successful Lockdown.

Surely Successful Lockdown means the worst is over?

A lockdown being successful only guarantees success if the lockdown remains.

Everywhere locations with an outbreak soon makes steps to ‘flatten the curve‘. This either results in:

  • outbreak slowing: cases numbers per day still increasing, but at a reduced rate
  • lockdown peak: case numbers per day starting to fall while under lockdown

Either of these outcomes could be considered to signal a successful lockdown. This section examines each of these two scenarios.

There can be an appearance of a graph of the progress of an outbreak, starting to look like an outbreak curve nearing or even past the peak. But rather than get too excited, the next two sections reveal how at best this is a ‘lockdown peak’. A peak not on this simplest diagrams of an outbreak, but the only real explanation given that neither of the events than can end an outbreak are at all close.

Outbreak Slowing (but not yet dropping)?

If the outbreak is slowing following a lockdown, it would seem there are three possibilities:

  1. too early: the lockdown will soon see case number starting to fall, it is just too early
  2. the peak is further than ever: reduction of case numbers means it will take even longer to reach a peak
  3. a lockdown peak is close: the lockdown has resulted in cases decreasing, which means peak of the curve must be close

Now check the flattening the curve diagrams. Simplistically, moving from the red ‘before’ curve, to blue after curve will result a drop in cases. However, flattening the curve does not bring the peak of an outbreak forward. Daily case number will slow with the move to the flattened curve, but the peak is delayed.

Flattening the curve will delay the peak. If the peak is near, it is because the cumulative number of cases is now high enough. Determining if case 1,2 or 3 is applicable can be determined by how long since the current level of lockdown began. Lockdowns can be expected to achieve their full impact within three infection cycles, which with Covid-19 is around six weeks.

If the lockdown started:

  • less than six weeks ago?
    • assume case 1 that is it too early to tell
  • less than 8 weeks ago?
    • if case rates are slowing it is probably just the move to the lockdown curve and the peak is further away than ever
  • more than eight weeks ago?
    • given cases are slowing now, it could be a ‘lockdown peak’ is approaching, but that does not mean the end is near

A Lockdown Peak.

What if cases numbers per day are now falling? Clearly there has been a peak. What is this peak if the requirements for ending a lockdown are not being met?

As per curve 3 from ‘flattening the curve‘, lockdown measures switch an outbreak from a spread factor as high as three (3.0) typical of Covid-19, directly to a spread factor of less than 1.0, resulting case numbers starting to fall as soon as the lockdown is effective.

While the lockdown is active, the curve ‘flattens’. In the case of spread rate below 1.0, new case numbers will continue to decline while the lockdown remains. Remove the lockdown, and the orignal Covid-19 curve returns. The earlier the lockdown took place, the more dramatic the result of moving the lockdown.

can result in spread rates This lowering of case number due to the move to lockdown will no longer apply Unless the lockdown has been running for two months prir Lower case numbers are not a sign the end is near. Remove the social distancing measures, and infection rates will return to the original pattern.

The only way a Covid-19 curve will reach real peak, is if approximately 50% of the population have been infected.

Any other ‘peak’ only reflects conditions during the lockdown. A ‘during lockdown peak. The end is only as near as total number of cases is near to reaching 50% of the population.

Endgames: Lessons From History

The Choices

Spanish Flu in 1918: Herd Immunity, But at a cost!

No solution other that herd immunity was found for the 1918 epidemic.

Herd immunity, has ‘had a bad rap’, has been taken to mean ‘do nothing’, and is generally misunderstood. In fact, the popular phrase ‘flatten the curve’, was conceived as describing a strategy for ‘reducing the cost of herd immunity strategy’. Improved herd immunity is discussed in detail below, but the fundamentals, which are that approximately 50% of the population must be infected, still remain.

The 1918 Spanish flu ended as a result of herd immunity. But it is estimated 100 million people lost their lives on the path to that herd immunity. Best practice was to use an improved herd immunity strategy, also known as ‘flatten the curve’, but no country ended the outbreak other than as a result of herd immunity.

Swine Flu, SARS, MERS: Global Eradication

None of these had were quite as difficult to confine the spread is with Covid-19, but in each case the solution was global eradication through the same approach as lockdowns and track and trace with Covid-19.

There were vaccines developed, but none the was found to be effective. There were no cures, and certainly no outbreaks that reached herd immunity.

If recent history is to be considered, perhaps global erdaication needs further consideration?

Influenza, the common cold: Still here!

There are vaccines for Influenza. Each year it is enhanced. Having a vaccine does not provide immunity, not does having had influenza one year provide enduring immunity into the future.

How many cases of the common cold have you had? There is no cure, nor a vaccine, although the disease results in quite a mild illness. What is clear is having a common cold does not provide lasting immunity.

The clear lesson here is that immunity following an infection can be short lived. Imagine all the deaths that would result for sufficient infections for herd immunity for Covid-19, only to find that immunity only lasts a single year?

Endgame #1: Herd Immunity.

What is Herd Immunity?

In reality ‘herd immunity’ can occur as a result of Over time, more people become infected by the virus and as a result become immune. This provides a continually rising percentage of immune people. Having a percentage of immune people slows the spread of the virus, so as the percentage of immune people rises, the rate of spread slows. The slowing rate of spread will at some point reach a level where cases are no longer increasing. This point is the point of herd immunity. A more detailed explanation is on the ‘curve’ page.

Herd Immunity with a Flattened Curve.

Hopefully you have seen graphs of ‘flattening the curve before’, but just in case, here is another one. While the ‘unmanaged’ red curve has a high number of cases at the peak, as shown in the blue ‘managed’ curve, it is possible to reach herd immunity by using a managed, or ‘flattened’ curve without overloading the health system. Note that the curve itself, is result of the rising herd immunity throughout the epidemic.

Are We There Yet(or even close)?

Events should have Italy in one of the best positions to be reaching herd immunity. There have been (as at April 6th), 132,000 confirmed cases. It is clear there are also cases that are not confirmed, so the real case load is higher. But how much higher? 60% of the Italian population is 60 million x 60% = 36 million. In summary, if real cases are approximately 10x higher than confirmed cases, then even Italy is only around 1/36 of the way to herd immunity.

Considering the above example, at this time, there is no evidence of any country being anywhere near herd immunity levels. Which means no-one has reached the real flat point of their curve.

Given no country is even close to herd immunity yet, then every country currently in lock down would soon return to the need for another lockdown if life went back to pre-lockdown conditions. That is, a lockdown ending soon is not an endgame. A lockdown ending well before herd immunity only allows a holding pattern.

Endgame #2: Stop and Wait, a two Step Solution

Step 1:

The strategy is bring cases to a very low level, and contain cases at as low a level as possible until a new solutions arises. Although sometimes this approach is described as ‘eradication’, and the idea of completely going back to how things were, in practice the ‘eradication’ part is purely reducing cases to a level where there are more choices available to contain the outbreak.

This is effectively a ‘local containment’, or ‘stopping the curve’ strategy. In reality ‘eradication’ only means get cases to low enough level that containment is manageable. Containment means ensuring cases are kept below a threshold level, and are no growing. In other words, ‘no curve’.

Containment will be either following a short very tight lockdown to reduce cases (as being attempted in New Zealand, South Korea), or by starting before there are significant cases ( as per Taiwan, Singapore, Hong Kong). Track and trace and aggressive testing can allow society to still have everyone at work, or at school, and even going to restaurants most of the time while living with Covid-19. But even Singapore, where life has seemed relatively normal during containment, will now have a one month long lockdown. Getting numbers down does not allow a full return to normal life during containment, and containment does not allow reopening borders, foreign travel or foreign visitors except in exceptional circumstances.

Taiwan, Singapore, and Hong Kong all seem to show that if cases number are driven low enough, life can continue, at least most of time without lockdowns. However, this is life under Covid-19, with closed borders, and the constant fear of future lockdowns. This is not an end, this is a holding pattern while waiting for a solution.

So for the end of lockdown that is not part of a herd immunity plan, even if the lockdown ends with no new cases being reported, there can be no ‘return to a fully normal life’. Many things remain on hold until something ends the outbreak, and if cases are now low, that end will not come via herd immunity.

Welcome to ‘containment’. Effectively a ‘holding pattern’, with constant monitoring for the possible need for new lockdowns if new cases arrive.

Step 2: Cure/Vaccine: ending the wait.

If there is a cure, containment can be lifted allow cases to rise with a ‘flatten the curve’ pattern, but now with the ability to cure patients and prevent serious illness or death. Relatively painless path to herd immunity.

Note that we still have no cure or vaccine for the ‘the common cold’, itself another coronavirus. There are at least 60 vaccines for Covid-19 already under development, with some already undergoing trials. Professor Damien Purcell , from the Doherty Institute, on 7:30 Report 6th April (at 8m35), tells of how a vaccine to produce antibodies in the upper nose and throat is more difficult that with other types of infection. How it is easy to have a vaccine the trigger production of antibodies, but how things can still go very wrong and how a vaccine for SARS-1 ended up accelerating the disease when tested on living subjects.

Vaccines are challenging and claims that we are at least 12 to 18 months away from a vaccine, are not promising ‘we will have a vaccine in 12 to 18 months’.

Cures can be brought to market more quickly. These can make living with Covid-19 more tolerable. But no ‘cure’ for ‘the flu’, or ‘the common cold’ does more than decrease severity. No cure for the flu so far ensures no one dies. And this is after how many years?

Step 2b?: Global Eradication to End the wait?

Another possible ‘end of the holding pattern’ would be if every country managed the cases in their holding pattern until there are no more cases anywhere. Then border could all open. No one had herd immunity to Covid-19 prior to 2020 and everything was fine, could it be possible to totally eliminate this virus?

Note that sometimes diseases that seem to be eradicated, can reappear. Ebola for example. A reason for this is that even if a disease is eradicated in humans, other organisms (such as fruit bats with Ebola) can still host the virus. Sometimes these other organisms (as with the fruit bats with Ebola) can even be asymptomatic. So a disease that has been eradicated in humans, can still exist in other animals, which in turn can lead to a reinfection of humans.

As far as we know, no human was infected with this coronavirus (Sars-Cov-2) prior to 2019, so perhaps the risk of a new outbreak is also low. On the other hand, perhaps the risk is not so low now. Even a tiger at a zoo has recently contracted Covid-19. If a tiger can contract Covid-19, perhaps many other animals can also. Have we created a worldwide outbreak that extends beyond humans, can could be given back to humans in future?

Calculating The Costs

Why the mortality rate from Flattening the Curve?

Comparing economic costs of the options will be covered in a separate post. This post only includes the cost in terms of human life, and as the since the eradication/containment option focuses on avoiding every possible case, focusing on fatalities comes down to considering trying to estimate the mortality rate as s consequence of herd immunity. Between flattening the curve and other measures, how low can cost become. I find it difficult to even start any comparison of options, before at least having a feel for how many lives must be lost with the herd immunity strategies.

The History

The term ‘herd’ may sound kind of wild, and clearly makes people imagine an unmanaged outbreak, so feel free to use the term ‘community immunity’ if it is more pleasing.

Herd immunity is the only proven way to end an outbreak. Neither of the above ‘end of lockdown’ scenarios has any guarantee of when, or even if, such an outcome may be achieved.

In the 1918 ‘Spanish’ Flu Pandemic, the solution was herd immunity, but at a substantial cost. According to some estimates, around 100 million lives were lost, representing 5% of the people on the planet.

In that outbreak it was observed that in locations where authorities took steps to ‘flatten the curve’, mortality rates were lower than elsewhere. Note the solution to the outbreak was still ‘herd immunity’, with the number of cases seeing little change where the curve was ‘flattened’. The result of this ‘flattening the curve’ was reduced mortality rates, not reduced cases. If the solution is ‘herd immunity’, cases numbers still need to reflect 60% of the population, but you can reduce mortality rates through better health care. ‘Social distancing’ is a strategy to reduce spread-factor and deliver ‘flatten the curve’, enabling reducing mortality rates, by enabling the medical system to cope and be able to prevent many deaths.

A way to further reduce mortatlity rates could It has been noted that the elderly and those with pre-existing medical conditions have far higher mortality rates than others. If you could remove these people from exposure, mortality rates for Covid-19 could see a significant further reduction.

The Data: What can we trust?

Estimated mortality rates of Covid-19 vary between 3.8% and 0.2%. This huge variation is because two factors greatly exaggerate the mortality rate. The first point to understand is that most cases are reported from locations where society feels overrun by the caseload they face. When overrun, testing can be limited to those who are already in need of hospital care, and of those who do need hospital care, there can be increased mortality due to an overrun medical system. So many cases are not reported, and there are more deaths that would happen if the system was not overrun.

The Reality.

In the USA there have been predictions of 240,000 deaths, even with ‘social distancing’.

With 327 million people, herd immunity would require 327 x 60% = 200 million cases. 240,000 deaths would from 200 million cases would be a mortality rate of 0.12 percent. With figures quoted by US medical advisors or 0.2% as an overall mortality rate, then 0.12% being the rate for people excluding the elderly and many of those with medical problems seems achievable. It also seems that projected mortalities does fit with a plan to achieve herd immunity.

As of today, 7th of April, the US has just recorded its worst ever day with just over 1,300 deaths, but some evidence this could be the current peak. Still there are projections this could be the worst week ever for America. If the current mortalities continued for a week at the 1,300 level, that another 9,100 deaths, almost doubling total fatalities within a single week. Now consider, a total of 240,000 deaths over 6 months would mean the 1,300 per day being the average (not the peak) day over the entire 6 months.

Conclusion.

Lifting a lockdown: The risks

Check the Data

The are various reports of ‘the peak is approaching’ and we are flattening the curve. However, considering the points raised above in ‘but what does it take to reach herd immunity’, it is clear any peaks or flattening being seen at this time is the result of ‘social distancing’, and as a result moving to a new ‘curve’ pattern, with the spread-rate being the spread rate with social distancing in place.

Moving to a new pattern will mean a different pattern of cases. Social distancing is all about what happens within the community, while much of initial testing, initial cases, and even initial deaths, are a result of travel across borders that will remain closed for now. The data to be considered is local community infection data only for:

  • confirmed and if available statistical case data
  • hospital adminisions from local transmission
  • deaths from local transmission

Note that confirmed cases may be less reliable than hospital admission data. It is essential to judge the effects of only the elements of the lockdown that would change in future. If cases have dropped significantly due to closing borders, this could lead to overestimates on the contribution of social distancing.

Review the Flattening Trend.

Having checked the data, what is the trend of local transmission experienced under lockdown? Are cases actually dropping as with even the runaway outbreak in Wuhan? If cases are dropping, or then congratulations, as in Wuhan, remaining in lockdown will see cases trend towards eradication, or close enough to eradication and the ‘eradication/containment‘ endgame is an option.

If cases are actually static, then in theory, just holding will eventually see the cases start to decline because of increased immunity, and if the medical system is near its limit, then the choices are to increase distancing further enabling a move towards eradication, or leave things as they are and head towards here immunity.

If the cure is still upwards, modelling is required to decide what changes may be needed to achieve either of the possible endgames, in order to then make a choice.

The reality is any ‘calm’ is temporary. The calm is a chance to decide which path to choose between:

  • commit to the number of cases required for herd immunity and the whatever fatalities arises as a result of choices made in how to manage the outbreak
  • try and stop the curve and stay in a holding pattern until medical science finds a solution

Conclusion

Deciding on an endgame is fraught with risks.

But any lifting of lockdowns at this time will really only be a relaxation of lockdowns, as resuming the curve is just crazy.

This means a path of containment. Any level of containment below the threshold of the medical system if following ‘herd immunity’, and a lower level of cases during containment if following a path of that ends with vaccine/cure or global eradication.

I am not a virologist, just a professional at applying logic. Here is an article quoting University of Melbourne epidemiologist Tony Blakely. The problem I have is that while I do not question the science quoted, I do question the logic and the ethics involved. The 30,000 deaths in Australia projected is as possible for herd immunity is already a high number, but there are risks it could go horribly wrong and the outcome be far worse. One of my next posts will examine the risk and ethical choices required.

But the worst outcome of all results from no choice being made.


Footnotes:

The cost of Containment

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