The very good news being reported in many countries is that we are past the first peak, especially in those which have enacted lockdown type restrictions. Even better is that we have not seen a rapid move to a second peak as restrictions have started to be lifted.
What is a Second Wave?
I only recently understood that this term has two different meanings, a medical definition and one which most people mean, and this can cause a lot of confusion.
Medical definition:
“Second wave: A phenomenon of infections that can develop during a pandemic. The disease infects one group of people first. Infections appear to decrease. And then, infections increase in a different part of the population, resulting in a second wave of infections”
Spanish flu is a well-known example of this. In the spring of 1918, in the first wave, it is estimated that 75% of the French military were infected. The virus spread peaked and then declined due to the internal dynamics of the virus – the susceptibility and immunity of the population. One theory assumes it then mutated to a far more deadly form returning in the autumn with a much higher mortality rate which is the “second wave” we see in the chart below.
What most people mean:
“Second wave – rising infection and death rates to a level similar to or greater than what we saw in early April.”
What is the difference?
In the current situation, measures were implemented to stop the spread of the virus. This created a peak but not from the internal dynamics of the virus, such as growing levels of immunity in the population. We could easily never see a “second wave” using the medical definition whilst having a new peak in infections and deaths many times larger than what we have seen so far as the first wave continues after interruption. This “second peak” in infections could be defined as the completion of the “first wave”.
A simple projection would be that the rest of the country reaches infection levels seen in London and New York. The results of the antibodies tests last month in the UK were that 17% of Londoners had had the virus and only 3% of people in the rest of the country.
It could of course be far higher if the lockdowns in London and New York had prevented far larger outbreaks there.
Let’s look at the question we really want to be answered
Will there be a second peak?
Some people are arguing that we will not see a second peak in COVID-19. Let’s look at the key arguments.
- Why should there be?
This is the view of Prof Pennington, a retired microbiologist, whose opinion has received a great deal of sympathetic coverage in the Telegraph and Daily Mail. “I think it’s very unlikely that there will be a second wave” as people are relying on models based upon flu which are not relevant to Covid.
This is an interesting point as flu mutates very quickly which is why we have so little resistance every year. Mutations then expose new parts of the population which drives a second wave. For COVID-19 so far, there has been a very limited mutation of the virus https://www.livescience.com/coronavirus-mutation-rate.html which is a good reason to think that there may not be a second wave.
If this is what he means then I likely agree, but it is not what people care about. What people care about is a second peak. This does not require the virus to change but simply for people not yet infected to become exposed.
- The virus is getting less deadly
Some researchers in Italy have suggested this but it has been widely discounted. It may resurface as a theory as it would be great if it were true, although it is worth noting it runs opposite to the logic from the previous point that the virus is not mutating.
I have heard a few people confident that viruses get less dangerous over time, but I have not found any evidence to support this. For example, as mentioned in the introduction, the second wave of Spanish flu had a much higher mortality rate which is potential because it mutated into a more deadly form.
- The Lockdown policies we have relaxed so far are safe.
This seems a pretty reasonable idea. The main source of transmission comes from being indoors and spending time close to others and we have adapted our behaviour to social distancing and handwashing. The main easing of restrictions so far has been in areas which are the least dangerous, for example socialising outside.
Looking at infection data it is likely that the R number has risen a little with these measures, to perhaps just under 1 in the UK, perhaps around 1 in much of the US and still perhaps below 1 in some EU countries.
A best-case theory to support this would be that the big driver of transmission is a few “super-spreaders”. It is a few people who pass it to perhaps hundreds, not the vast majority passing it to a few. In this case the restrictions on mass gatherings such as sporting events would make an outsized difference allowing other activities to carry on largely unaffected.
If this hypothesis is correct, it is important to carefully track what happens as we relax the restrictions. In the UK, it is critical but made difficult by the number of simultaneous easings we are seeing at the moment. For the US and UK, we also need to be vigilant as we are relaxing restrictions with infection rates far above other countries who are doing the same.
- We are already immune
This remains rather a fringe view that we have already reached herd immunity, notably pushed by Professors Gupta, of the Oxford study, and Friston.
Prof Gupta is extremely optimistic and expects a release of lockdown to not lead to a resurgence in case numbers. She thinks the fall in case and death numbers “the driving force was the build-up of immunity” not lockdown and the first wave was completed with a massive spread of the virus and a majority of non-symptomatic cases.
Unfortunately, her view requires several important leaps which I cannot follow. For example, the antibodies test data suggest that only 7% of the population have been infected but she conjectures that more people have been infected but for some reason do not have the antibodies. In addition, I have struggled to understand how the Infection Fatality Rate can be “definitely less than 1 in 1000 and probably closer to 1 in 10,000” since more than 1 in 1000 people has ALREADY died from COVID in the UK.
Furthermore, if all of the countries has already been infected why is it overwhelmingly Londoners who have been ill?
Prof Friston has been getting a lot of press for this model recently. It is rather complex, hidden behind some fiendish maths adapted from physics. In essence, his model does not conclude that lockdowns had no effect, it assumes it. After assuming lockdowns and policy are irrelevant, he has to find other variables to cause the peak in infections and his proposal is slightly different from Gupta’s. It is not that we have all already been infected by the virus, it is that perhaps 80% of us were immune already. He looks at the UK and Germany and concludes there is an immunity difference in the populations that makes lots more Germans immune to COVID than British people.
I have not seen his opinion on why Brazil’s death rate keeps rising but since it cannot be their lack of lockdown it must be because Brazilians are naturally less immune than everyone else or we are about to see a rapid spontaneous fall in Brazil’s cases.
- Summer makes a difference
It seems certain that this is true to some extent. We still see outbreaks in warm countries, but there is some indication that warm weather and higher humidity affects the virus and, of course, in hotter climate behaviours are likely to be different anyway in terms of socialising outside.
Summary
Unfortunately, I do not agree with the most optimistic arguments that there is no risk of easing lockdown. Since we are so much safer outside than inside, and as approach summer it may well be that we will not see a rapid resurgence of the virus which will give us all some respite and time to reassess our approach.
Applied Macro 