The second wave of the ongoing Covid-19 pandemic has receded and the people have had enough of restrictions. There is immense pressure to end the lockdowns and many politicians will do as their voters wish. But there will be a third wave and it is likely to become larger than the second one. Below I try to explain why that is the case and what it means for our societies. My conclusions may sound alarmist, and I may be all wrong, but the scenario is neither impossible nor am I the only one who thinks it is likely.
The Spanish Flu came in three waves spread over 18 month. By summer 1919 most populations had gained some immunity against it. During the winter flu season of 1919 the new disease was no longer a public danger.
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Here is the similar curve for the United States during the Covid-19 pandemic.
The U.S. just finished what – in comparison to 1918/19 – is the second wave of the pandemic.
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The situation is similar in large parts of the world. The Covid-19 pandemic has just finished its second wave.
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One or two weeks ago Europe and the U.S. reached the floor of the valley. From hereon it is another uphill climb. Despite continuing lockdown measures the rate of change of the number of new cases has already turned positive again. The number of new infections is growing again. The third wave has started.
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What factors are at play now and how may they effect the shape of a third wave?
New variants of the virus, pharmaceutical and non-pharmaceutical measures will each have certain effects. But the people's behavior will be the most important factor.
New variants:
In Europe as in the Americas the British B.1.1.7 variant of the virus is now becoming dominant. The strain is 50% more infectious and more deadly than the virus variants that have been circling so far. (There are additional variants of concern (VoC) which will become relevant in later phases, especially those which can infect people who are immune against the original virus.)
The numbers from Britain and Denmark show that it only takes a few weeks for a better adapted strain like B.1.1.7 to gain the upper hand.
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Pharmaceutical interventions:
We do not have proven medications which could help to suppress or heal Covid-19 infections. (Some candidates are still in development. Others, like Ivermectin, are still in trials.)
Luckily, and unlike in 1918/1919, we now have vaccines that work well at preventing serious illness and death. Studies from Israel (1, 2) and Scotland (1) show high vaccine effectiveness in the population. This stuff works.
But population wide vaccinations take time. At the current rate it is unlikely that vaccinations will be sufficient to suppress a third wave. They may dampen it a bit but that is all we can hope for.
The currently ongoing vaccination of priority groups, the people most endangered, will help to keep death within those groups down.
Non-pharmaceutical interventions:
Non-pharmaceutical measures like lockdowns and mask mandates have helped during the first and second wave to push the replication rate R below 1. But the next wave will come with a 50% more infectious variant of the virus. To keep the replication rate under 1 in the third wave would thus require stronger non-pharmaceutical measures to keep the virus under control.
The rate of increase of new cases in Denmark from week to week is now at 33%! This despite ongoing lockdown measures.
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Behavior:
There is a growing share of the population that ignores lockdown and mask mandates. These are not all Covidiots. The people have just had enough of it.
Arash @thekarami – 15:26 UTC · Feb 27, 2021
Replying to @thekaramiThese lockdowns are beginning to resemble the forever wars in that any time someone speaks against them you get a whole bunch of people screaming that we must continue until we reach an arbitrary and ever moving goal.
And for those of you who are new, I’m not a covid denier, I’m not anti-mask, my brother is a doctor at a hospital and impacted directly, I took this seriously for the first three months, six months, nine months but it’s been 12 months and they’re talking about 2022? 2022!? No.
Conclusion:
The third wave will come with a stronger virus gaining dominance. In some countries (esp. eastern Europe) most people already ignore the lockdown measures. It is unlikely that the authorities will be able to press for even stronger ones. We will have to surf this wave without the effects of most of them.
At the end of the Spanish Flu pandemic the population had reached some kind of herd immunity. Enough people were immune against the virus to prevent further large outbreaks. A large part of that herd immunity was achieved during the second wave of that pandemic when many, many people got infected. The third wave was therefore smaller than the second one.
In Europe and the U.S. we are, even after the second wave, far away from herd immunity. Less than 10%-15% of the populations has had the disease and achieved immunity. Immunity can be reached through infection or through vaccination. Over the next weeks we will only have enough vaccination capacity to immunize the most endanger 10 or 20% of the population. The other 70 to 80% are still not immune and still endangered.
All this makes it likely that the third wave of this pandemic, with a stronger virus, less effective interventions, little herd immunity, will become much bigger than the second wave. Instead of 250,000 new cases per day in the U.S. during the top of the second wave we may see 2.5 million new cases per day during the third wave.
There is one factor that may prevent that. It will get warmer and seasonality does play a role in respiratory infections. But mid June to August 2020 saw a strong increase of cases in the U.S. and South America and South Africa were hit strongly even during their summer time. I am therefore skeptical that seasonality will be of much help.
One may think that larger numbers of infections will not matter much as the most vulnerable people will have been vaccinated and are protected, that the hospitals will not become overwhelmed and that the number of deaths will not increase that much.
But that would be wrong.
About a quarter to a third of the U.S. population has a condition (overweight, diabetes) that makes it vulnerable to Covid-19. Not as much as very old people but still to a significant degree. At ten times the infection numbers of the second wave we will certainly see many more people in need of professional medical help than we did see before.
But the old people will have been vaccinated. The ICUs will not be filled with them like they were during the first and second wave. Younger folks, getting infected at a rate ten times higher than through the second wave, will fill the ICUs.
There will no longer be grandpas or grandmas of age dying from Covid-19 but mothers or fathers in the best years of their lives. The sum of years of life lost (YLL) during the third wave will therefore likely exceed the sum of the second wave.
It is difficult to say how long it will take for the third wave to reach its peak. As soon as lockdown measures end or fail we will again see strong exponential growth that may well exceed the growth we saw during previous waves. My hunch for the U.S. is that by the end of March to mid April it will be see the strongest growth so far of new cases.
Then again – that's just a hunch and I may be all wrong. In fact I hope that I am all wrong.