(Art design: Jean-Dominique Lavoix-Carli)
Long COVID could be the next battle we have to fight and win in our struggle against the COVID-19 pandemic.
Thus, in this article, we seek to assess Long COVID in the framework of the fifth wave of the COVID-19 pandemic. This will also give us possible indications regarding how Long COVID could develop in the future, beyond the current wave. Our aim is to obtain an idea of the current and coming impact of long COVID. This early assessment will, in turn, contribute to the development of responses and strategies to answer this aspect of the pandemic, which has been so far rather ignored.
First, we explain our methodology. Doing so, we uncover some incoherence among the few serious available data on long COVID. We suggest ways to overcome them for our purpose, strategic foresight and early warning. Then we present the result of our evaluation as three short scenarios for Long COVID and the fifth wave: “Coming back to our senses“, “Optimism“, and “The price of ignorance“.
The first article of this series on Long COVID reviews current knowledge up to end of November 2021 (Helene Lavoix, “Long COVID and the Fifth Wave – The Hidden Pandemic“, The Red Team Analysis Society, 22 November 2021). It lays the foundation for our understanding of the disease. We also use when needed what was established in our other articles on the fifth wave of the pandemic (Helene Lavoix, “The Fifth Wave of the COVID-19 Pandemic and Lethality“, 9 November 2021, and “Towards a Covid-19 Fifth Wave“, 27 October 2021, The Red Team Analysis Society).
Estimating Long COVID for the fifth wave
Objective and limitations
As highlighted in the introduction, our objective is to get an idea of the current and coming impact of Long COVID.
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For this, we need more than a global estimate of all people having suffered and suffering of Long COVID, such as what we found in the previous article, thanks notably to Chen Chen et al. (“Global Prevalence of Post-Acute Sequelae of COVID-19 (PASC) or Long COVID: A Meta-Analysis and Systematic Review“, MedRxiv [not yet peer-reviewed], 16 November 2021, doi: 10.1101/2021.11.15.21266377).
We need a global estimate of people experiencing Long COVID each day. We also need to know how many of these people, each day, can carry out or not their activities. Furthermore, as our aim is foresight and strategy for preparedness and response, we need to be able to make forecasts, however tentative. Therefore, we use what has so far been understood of Long COVID, that appears to depend notably on infections, and thus we consider the factors favouring or constraining the pandemic in terms of contagion (see “Towards a Covid-19 Fifth Wave“).
With these estimates, we should start being able to envision collective global impacts.
Considering the high level of uncertainty and the numerous approximations and estimates upon which we have to rely, what we shall get are mainly possible rough trends and indications (for an explanation of what are “indications”, see our seminal “Horizon Scanning and Monitoring for Warning: Definition and Practice“, The Red Team Analysis Society, revised ed., 2019).
Moreover, a major approximation that we carry out is to apply rates specific to the UK to the whole world. However, as the UK survey is the only national and historical data on Long COVID available, we do not have much choice. As explained below, we shall also, here, encounter a major problem, incoherence in data.
Hopefully, as countries start taking Long COVID into account, better assessments will become possible.
Estimated daily cases of Long COVID
Bearing in mind the limitations faced, we apply Chen Chen et al. (Ibid.) global pooled prevalence rate, 43%, on world daily cases of infection. This gives us an estimated daily number of Long COVID.
For the past, we use real statistical data of daily cases of infection or more precisely daily COVID-19 tested positive cases, an approximative indication for the number of infection (Our World in Data using COVID-19 Data Repository by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University). Note that even for past data, figures change every day, as corrections to datasets are made. Sometimes, important number of cases of infections are added a posteriori, more than one month later. This adds again another measure of uncertainty.
For the future, using our article “Towards a Covid-19 Fifth Wave“, we make three hypotheses or scenarios for the possible shape of the wave of daily global infections, as detailed below at the start of each scenario.
For all of these scenarios, we consider that the prevalence of Long COVID linked to the Omicron variant is the same as what we was observed with previous variants (WHO, “Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern” – 26 November 2021). We must, however, underline that this is an unknown. The Omicron variant could lead to more, less, none or far more cases of Long COVID. The intensity and various characteristics of Long COVID resulting from Omicron – or other future Variants of Concern (VoC) – could also change. The new symptoms could only be a couple of weeks of tiredness, or on the other end of the spectrum a far more severe Long COVID. This should be monitored. Even with monitoring, it will take months and even potentially years before we start having an idea of the impact of variant Omicron or other VoC on Long COVID.
Daily number of Long COVID according to length of Long COVID
The next step was meant to be, initially, relatively simple to realise. It would prove far more difficult to handle than planned.
Finding the rates of Long COVID according to duration
The idea, originally, was to “simply” apply the proportion of Long COVID according to duration to the estimated daily number of people that would experience Long COVID and that we had obtained with the previous step.
The proportion of long COVID per length of illness was to be given by the historical monthly datasets of the United Kingdom Office for National Statistics (UK ONS – Tables 1 – Estimates of the prevalence of self-reported long COVID and associated activity limitation, using UK Coronavirus (COVID-19) Infection Survey data- Monthly datasets). The evolution of that rate, since March 2021, is shown on the graph below, which depicts the evolution of Long COVID throughout time in the UK.
For example, on a given month, the lightest brown segment represents new cases of long COVID as a new wave starts, waxes then wanes. The following month, part of these new cases have moved to the next category (Long COVID lasting between 12 and 26 weeks) and thus are depicted as a segment of a slightly darker brown. The new “entrance” in a segment joins the Long COVID cases of previous months still in this category, while some Long COVID cases end and other Long COVID cases move to the next category (26 to 39 weeks). Thus, each month, Long COVID cases move from one column to the next, going each time one category up.
However, we could not just take the percentage resulting directly from the monthly British tables. Indeed the number of cases and the proportions for one month concern all these people who experiment Long COVID for a given month (or for the period under investigation). However, as explained in the previous paragraph, each segment, in fact, links to a different period of time as far as the triggering event, infection, is concerned. For example, the 31 October 2021 result concerns people who were infected after 1 November 2020 (Long COVID lasting more than 52 weeks), and people who were infected between 8 November 2020 and 31 January 2021 for these Long COVID lasting between 39 and 52 weeks, and people who were infected at other periods for each other segment.
As we want to be able to move forward in our assessment, starting from the infections, we cannot take the British tables directly. We have first to recreate tables according to the time of infection and then to deduce a tentative rate for each length of Long COVID we shall then apply to our daily number of Long COVID.
Uncovering problematic incoherence
• Long COVID lasting more than one year: when the number of Long COVID exceeds the number of detected positive cases
We started with the longest Long COVID, the real estimates of UK long COVID that last over 52 weeks. These Long COVID correspond to people who were infected, knowingly or not, at least 52 weeks before the survey. Thus, for example, people declaring a Long COVID that lasted more than 52 weeks on 6 March 2021 had to be infected before 7 March 2020, i.e. at the very beginning of the pandemic.
However, when we compiled the different statistics, we found a surprising result. If we use the UK historical series for Long COVID, as well as the reported official statistics for COVID positive cases, we see, as shown on the curves below, that until August 2021, the number of Long COVID that lasted more than one year (the brown curve) is superior to the cumulated number of people that had tested positive to COVID (the yellow curve). We thus have more people with long COVID than people who were detected as infected. This incoherence continues up until August 2021.
This statistical incoherence may stem from erroneous declarations (people badly estimated the start of their infection) and from largely unreported cases of infections, as people were infected, noticed it or not, did not report it and nonetheless developed long COVID. These two reasons are not mutually exclusive. We may, in any case, infer that a large part of asymptomatic cases were unreported and that they nonetheless developed long COVID.
With time, as more tests were done and as people probably became used to report their long COVID, biases were reduced. Yet, we remain with an enormous number of long COVID lasting more than 52 weeks, even for the last two monthly reports.
Furthermore, in the light of the British survey, the prevalence found by Chen Chen et al. (43%) cannot work for Long COVID lasting for more than a year. Indeed Chen Chen et al. (ibid) only looked at “prevalence for 30, 60, 90, and 120 days after index date”, i.e. 4 to 17,2 weeks. Thus, three and a half segments of the British survey are not included in Chen Chen et al. meta review. We can still, tentatively use Chen Chen et al. global pooled rate of prevalence, but only out of absence of alternative. In that case – a 43% prevalence for long COVID – the last UK figures would mean that all declared Long COVID will last for more than 52 weeks. Could this be true? It would be imperative to know.
• Potential meaning and consequences
If the numbers given by the British survey are representative, then we could have different explanations allowing to overcome the apparent incoherence.
The British figures could mean that a very large number of people infected with the SARS-CoV2 never completely recover, even if initially they do not feel any symptoms. This is the worst case scenario, because as infections spread, then cases of Long COVID of more than one year would also strongly increase.
Alternatively, the figures could also mean that those people who had a very long Long COVID initially were the most fragile, or the most predisposed to get Long COVID, and thus that their Long COVID lasted longer. With time, as infections rise, these people who are susceptible to get a very long Long COVID could become proportionally less numerous. In that case, the rate for a duration superior to 52 weeks will continue to fall, and maybe stabilise.
Actually, fundamentally, we do not know.
In this light, the British approach makes sense. By looking at the proportion of Long COVID compared to the overall UK population, the UK statisticians overcome the obstacle of detection of asymptomatic cases, as well as the challenge of variations in tests’ policies. However, they also make it difficult, if not impossible to anticipate. Thus, they have good indications to manage the present, but they cannot prepare for the future.
• Ways forward to handle this case in the framework of strategic foresight and early warning
In terms of foresight, this means it will truly be very difficult to estimate how many people could develop a Long COVID of more than 52 weeks in the future, starting from the identified number of infections.
As we want to be able to anticipate, considering the dearth of data, we can make the hypothesis that the final result for the last experimental statistics given by the UK (31 October 2021) is somewhat representative, despite biases probably remaining. This could be, in terms of rates, a kind of worst case scenario.
To give an idea of the immense uncertainty we face, we present below two curves, showing two estimates for Long COVID superior to 52 weeks (the brown dotted line): the first estimate was done with the UK statistics for 2 October 2021 and the second with the statistics for 31 October 2021.
As is obvious from these two curves, the results are varying wildly as we go, for end of May 2022, from more than 3,75 million of Long COVID lasting for more than a year to around 1,5 million.
If we make a similar calculation for each of the minimal duration for Long COVID as resulting from the British survey, we see that the curves all vary as shown on the figures below. The Long COVID curves follow more or less the curve of infections, in a flattened way, but without simple linear consistency of rates. As a result, it is difficult to discern simple trends, and our knowledge is so far too limited to create a more coherent model. Much research still needs to be done.
In such difficult cases for anticipation, notably as far as the long COVID cases superior to 52 weeks are concerned considering the potential numbers involved, we need to use scenarios added to early warning and to adjust scenarios as knowledge increases.
Here, we shall only focus on one scenario. We shall consider that the Long COVID rates per duration of Long COVID all correspond to the recalculated rates for the 31 October 2021 UK survey (latest data available at the time of writing).
These rates will be applied to the global daily rate of Long COVID (even though we know that the meta review by Chen Chen et al. does not cover 3,5 segments), for each of the corresponding length of Long COVID. For Long COVID longer than 52 weeks we shall conservatively consider that the length of the illness is only these 52 weeks. Again, this is a major approximation. Here also, scenarios would be needed to consider various lengths of this type of Long COVID that could be, for example, 1 year (this scenario), 2 years, or for ever (a HIV type of scenario).
Once more, we want to stress that, even for the scenario selected here, the result will, obviously, only be roughly indicative.
All these steps being done, we now have a rough indication of people suffering of Long COVID daily in the world.
Severity of long COVID
Finally, we need to know the impact of Long COVID on daily activities. In other words, each day, we want to roughly estimate how many people with Long COVID will be completely unable to carry out their activities, will be somehow limited in their activity and will not be limited at all.
Always using the UK ONS monthly survey, as far as the limitation of activity is concerned, rates vary little over months, as shown in the graph below. We shall take the latest rates, i.e. those for 31 October 2021, for our assessment. This time we can be slightly more confident in our assessment, apart from the fact that we apply British conditions to the whole world, when, most probably, the rates vary immensely according to countries.
Three Scenarios for Long COVID and the Fifth Wave
Resulting from our model*, we now have a rough daily number of people suffering from Long COVID estimated globally up until end of February 2022, furthermore sorted according to activity limitation. Using our earlier work on contagion (“Towards a Covid-19 Fifth Wave“), we created three scenarios to envision three possible shape for the fifth wave.**
We present these results first side by side to allow for comparison, then one scenario after the other. We detail more the narratives for scenario 2 and 3 than for scenario 1.
What we see, first, is that Long COVID hardly follows waves. Rather, the waves can be observed but are transformed into ondulations towards higher numbers of daily Long COVID. Only the second scenario seems to show a stabilisation at a very high level. The last scenario would lead us towards a staggering 140 millions people suffering of Long COVID each day.
Similarly a relatively large and slowly rising share of the world population is limited in its daily activity, either slightly or a lot, a share that accelerates in the third scenario.
Scenario 1: Coming back to our senses
The first scenario considers that the global fifth wave of infection will follow a pattern similar to the second wave.
Borders have been more reopened than for the third and fourth wave, and non-pharmaceutical interventions as well as cautiousness have also been relaxed, considering notably an erroneous understanding of current vaccination and willingness to go back to a pre-pandemic world. Nonetheless, as infections rise, measures are reintroduced. The new Omicron variant is finally found as being highly infectious, as suspected initially; the “increased risk of reinfection” is also confirmed with time (WHO, “Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern” – 26 November 2021; Juliet R.C. Pulliam et al., “Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa“, medRxiv [not yet peer-reviewed], 2 Dec 2021, 2021.11.11.21266068; doi).
The pattern of the fifth wave thus “looks” like the second wave, at a slightly higher level because of temporary complacency and because of the Omicron variant.
Daily, towards the end of December 2021, 110 million people in the world suffer of Long COVID. It is especially hard for those 21 million people and their families who cannot at all assume their daily activities.
The costs on individuals, families, companies, sectors and countries that started appearing previously do not relent. On the contrary, they go on and increase.
Scenario 2: Optimism
This is the most optimistic scenario. The pattern of the fifth wave looks like the pattern of the fourth wave.
The factors that could lead to this scenario would be vaccination that become more widespread worldwide while it reduces somehow infection. We also have a very positive impact on infections of the third dose or booster dose in those countries that had so far largely driven infections and lethality (Tal Patalon et al., “Odds of Testing Positive for SARS-CoV-2 Following Receipt of 3 vs 2 Doses of the BNT162b2 mRNA Vaccine“, JAMA Intern Med. Published online November 30, 2021, doi:10.1001/jamainternmed.2021.7382). Finally, the Omicron variant, despite being very infectious, has led to reinstate more reason and common sense in various policies and behaviour. As a result, we are in a situation that is more similar to what was done during the fourth wave.
The fifth wave in scenario 2 looks very much like the fourth. It is only very slightly stronger to account for the Omicron variant.
Daily, towards the end of December 2021, the number of people in the world who suffer of Long COVID seems to stabilise and even to become very slightly lower around 107 million cases. This number remains enormous, but, at least, it does not increase anymore. Life remains especially hard for those 20 million people and their families, who cannot at all assume their daily activities.
The costs on individuals, families, companies, sectors and countries that started appearing previously go on. However, the stabilisation, even at a high level allows for a modicum of adaptation. True enough, those sectors that have been disrupted will not really be able to go back immediately to what they were before the pandemic, but the alternative solutions that were imagined could be sufficient. Of course, this means that these solutions will have to last at least a couple of months more.
Scenario 3: The price of ignorance
This scenario is probably the most worrying. The pattern of the fifth wave for the infections would look like the first wave: global infections would rise to reach a new and higher plateau.
This scenario is grounded in a change of priorities, with the primary concern, worldwide, given to the return of an economic system similar or as similar as possible to what existed before the pandemic. Vaccination strongly lowers the number of severe forms of COVID-19 necessitating hospitalisation, as well as mortality. Thus, those cases of COVID-19 that remain, despite the daily load of deaths and sufferings, are deemed as acceptable for the sake of conserving the existing socio-politico-economic system. In most countries, policies and behaviour aim thus, as much as possible, to ignore the still continuing pandemic. Thus, infections rise, but do not trigger the type of responses that would be necessary to stop global contagion.
The arrival of the Omicron variant, past a few first weeks of return to caution, does not change policies and behaviour. Under pressure from the UN bodies and various actors, hinderance to travels and the few closure of borders that had been temporarily reinstated are abandoned. This is done even before we can assess with certainty the severity of the forms of COVID-19 triggered by the Omicron variant and definitely before any link or absence thereof to Long COVID can be made and understood. This is done even though the strong infectious power of the Omicron variant is confirmed.
As a result, the fifth wave looks like the first, but at a much higher level. In our timeframe (four months), it does not stop rising. Probably, it would continue going up and up until new more adequate policies are designed, or until the SARS-CoV-2 and the COVID-19 disappear or become benign.
The number of people in the world who, daily, suffer of long COVID seems to never stop rising. It does increase less steeply than infections, but it reaches new heights every day, up to almost 140 million cases at the end of February 2022. Life remains especially hard for those 26 million people and their families who cannot at all assume their daily activities.
The costs on individuals, families, companies, sectors and countries that started appearing previously continue to rise. The disruptions that were partly stemming from Long COVID intensify. As Long COVID is not monitored and has been rising without awareness and care, disruptions erupt haphazardly and pile up. Production, logistics, services are hit and new solutions must be found. Cascading effects cannot always be stopped. On the contrary, domino effects increase as more and more people become prey to Long Covid.
Consommation also takes a toll. Indeed, people struggling and suffering, as well as their families, not only have less disposable income but also revise their priorities and are less encline to consume (e.g. Patrick W. Watson “The “Long COVID” Economy“, Forbes, 14 June 2021 using a commentary by David R. Kotok, “M2 Velocity, Fed & Years Life Lost (YLL)“, Cumberland Advisors, 27 April 2021).
China, which now fully benefits from its insistence on a zero COVID policy, is almost free, relatively, of the dire effects of long COVID (e.g. Helene Lavoix, “How China Could Win the War against the Covid-19 Pandemic“, The Red Team Analysis Society, 18 January 2021). Those countries like Australia or New Zealand who also kept their borders closed for a long time reap benefit of their cautious policy.
In the harsh context of great-power struggle and competition that is taking place internationally, China, unburdened by Long COVID, enjoys a very large relative advantage, directly and indirectly as it can showcase its foresight and acumen. On the other hand, Europe and the U.S. now must carry the ever increasing weight of Long COVID. At worst and on the long run, if Europe and the U.S. do not act and thus if they continue letting infections spread and Long COVID rule, China will have won the international contest simply by default of its adversaries.
Despite the many uncertainties and limitations highlighted, it is clear that the real impact of the COVID-19 pandemic definitely and imperatively must take into account Long COVID. The more the world in general, a country in particular, faces infections, the higher its burden in terms of sufferings, economic and financial cost, and disruptions. For countries, to these already immense burdens we must add loss of power, absolute and relative.
Further research would be needed to estimate more finely possible impacts, including through comparisons with previous pandemics. How resilient are the various systems within which we live, when confronted to this kind of grinding weight?
Long COVID is fundamentally disruptive, including because of the dearth of data and the absence of understanding we face. Data must be gathered, knowledge must be accumulated, treatments must be found and, waiting for these, solutions must be imagined. Policies considering Long COVID must be designed and implemented.
The price to pay to live with the COVID-19 without considering Long COVID may well be far too high to pay.
*We used the dataset for 30 November 2021 (Our World in Data using the COVID-19 Data Repository by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.). It is likely the slight drop in global infections at the end of the period results from the U.S. and the absence of testing and data over Thanksgiving, from Thursday to Sunday.
**Considering the dearth of knowledge and data on long COVID, the number of estimates and approximations, without forgetting the incoherence uncovered, we do not give probabilities for each of these scenarios, which are, at this stage, merely indications aiming at framing the issue.