What is our COVID endgame?

As we enter the second year of the pandemic many people are frustrated with continued restrictions and there is a lot of pressure to ease COVID restrictions. Some people vocally resist such pressure, acting as if it is irresponsible to open up when COVID numbers are still high. Most of the arguments on this topic depend on either COVID fatigue or the desire to be responsible. Few seem to realise that the situation has changed: restrictions that made sense at the beginning of the pandemic do not make sense any longer.

Covid is a very transmissible disease.  Disease transmission is typically measured by R0, which is the number of new people each infected person will transmit the disease to before they recover. The first waves of COVID had R0s in the 2-3 range, the delta variant had a R0 about double that, and omicron is estimated to have a R0 of around 10.  

The R0 of a disease determines what happens if a few cases of the disease enter a population.  If the R0 of the disease is less than 1 the disease will eventually die out.  Since each infected person will infect less than one person, every generation of the disease will have fewer infections, until the disease is gone.  In contrast, if the R0 is greater than 1 each infected person will transmit the disease to more people, and the disease will, given enough time, spread to everyone in the population. 

R0 can of course vary depending on the circumstances.  To use an extreme example, if each infected person never interacts with anyone else during the time they are infected they obviously can’t infect anyone, so the R0 effectively drops to zero.  R0s are relative to a particular set of societal behaviours.   

With many diseases being infected once protects against being infected again. In that case, the disease can sometimes stop before everyone in the population has been infected. This concept is known as herd immunity. For example, suppose a disease has a R0 of 1.5.  The disease spreads, but after 50 percent of the population has it half of the people that the disease would be spread to are immune.  The effective R0 of the disease thus drops to .75, and the disease dies out in the population. Clearly, the percent of the population that must be infected before herd immunity is reached depends on the R0, with very infectious diseases requiring almost the entire population to be infected before herd immunity is reached. It isn’t clear the extent to which people can be reinfected with COVID, so whether the concept of herd immunity applies is unclear.  

The conclusion of all of the above is that there are only two long term outcomes after a very contageous disease enters the population: either the number of cases within the population goes to zero due to public health measures that reduce R0, or enough people get the disease that herd immunity is reached.  For diseases with a very high R0, that means practically the entire population will be infected.

One strategy that some countries have followed during the recent epidemic is to attempt to get COVID numbers to zero and keep them there.  Countries such as New Zealand and China followed this “zero COVID” strategy.  Doing so required incredibly harsh lockdowns until the countries were COVID free.  Even a few people not following the rules could invalidate the entire strategy.   After there were no COVID cases, borders needed to be monitored to ensure that no new COVID cases arrive.  If new COVID cases arrived, regions had to be locked down until it could be ensured that COVID numbers were again at zero.

The upshot of the above strategy is that aside from the restrictions on travel, after COVID numbers are zero life can basically go back to normal.  The downside is that border restrictions have to be maintained permanently, and that the initial lockdowns must be incredibly strict.  The lockdowns must also be maintained until it is certain that COVID cases have reached zero.

Western countries largely did not follow a zero COVID strategy.  There were always enough exceptions to lockdowns that a small number of COVID cases remained.  Western countries also generally did not put strict border controls in place.

Instead, western countries followed a soft lockdown strategy. They went into lockdown whenever covid cases got above a certain number, to attempt to halt the spread of the disease.  Soft lockdowns can reduce the number of people infected within a certain time period, however they can never eliminate COVID.  It is a mathematical fact that opening up while there are any cases of a very infectious disease will eventually cause cases to rise very high.  Allowing even one new case into the country ensures that case numbers will balloon until the point where lockdowns must continue. The soft lockdown strategy that western countries adopted was thus never a long term solution to COVID.  Soft lockdowns only make sense as a stopgap strategy until some other solution can be found, for example until vaccines arrive. 

Unfortunately, vaccines do not appear able to eliminate COVID in the population. If vaccines prevent infection they can create herd immunity in a population, in a manner similar to how previous infection does.  Even if they don’t entirely prevent infection, vaccines can still potentially create herd immunity if they are reduce transmission enough that R0 drops below 1.   Unfortunately vaccines do not appear able to reduce R0 to the required level.  They do reduce transmission, however the fact that even countries with high vaccination rates have had high levels of COVID shows that herd immunity is unrealistic.

The main benefit of vaccines instead appears to be that it reduces the severity of the disease in infected people. Vaccinated people are much less likely to be hospitalised if they are infected with COVID, and have lower death rates. By delaying infections until after people are vaccinated soft lockdown strategies have thus saved a lot of lives. 

It is becoming clear that many people do not seem to realise that soft lockdowns only ever made sense as a temporary strategy. Locking down whenever COVID numbers get high but not reducing COVID to zero is a commitment to rolling lockdowns in perpetuity. Given that the natural stopping point of the soft lockdown strategy has been reached a reevaluation of COVID strategy is in order. 

One option might be to move to a zero COVID strategy.  However that ship has almost certainly sailed.  The time for zero COVID was immediately, when the disease was less transmissible, more deadly, and people had not already been in varying states of lockdown for a year.  The idea that people will accept harsher lockdowns than we have had yet after a year of COVID fatigue seems crazy, especially when new variants are less deadly than the previous ones and many people are vaccinated.  Additionally, public health officials do not have the credibility to pursue a zero COVID strategy. Given the lack of willingness to commit to a zero COVID strategy when it made sense to do so I suspect any zero COVID strategy would effectively turn into an almost zero COVID strategy, which would necessitate another round of lockdowns after the disease has had time to spread.  

It is also unclear that zero COVID is even possible given the very high R0s of new variants.  It is possible that a single case that slips through border controls could require the whole country to be locked down every time given how transmissible omicron is, which could mean a zero COVID strategy no longer makes sense.  Countries such as China may need to reevaluate their COVID strategy in the near future.

The other option is to simply abandon restrictions.  There are several things that make abandoning restrictions now a far less bad outcome than simply ignoring the virus at the start of the pandemic would have been.  Omicron is less deadly than other variants, and vaccination reduces the likelihood of serious infection further.  But the main reason to abandon pandemic restrictions is that there is no other realistic option. Zero COVID is infeasible, and continuing soft lockdowns forever is not something that should be seriously considered.

Generally the discourse around the whole pandemic has been abysmal.  Most people seem either to believe that the pandemic is no big deal and we shouldn’t do anything about it, or that COVID is terrible and all restrictions are justified.  There was no discussion in the early stages of the pandemic of soft lockdowns vs a zero COVID strategy, and this likely led to both more deaths and longer lockdowns than were necessary in many western countries.  So I am not hopeful that people will realise that the soft lockdown strategy most western nations followed has run its course, and that, despite the high levels of COVID that will inevitably result, easing pandemic restrictions is the only remaining option.  

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