Two paths to controlling COVID with vaccinations

 

As vaccination is rolled out across advanced economies, the main danger has become mutations of the virus, or variants. We all know about the B.1.1.7 variant that emerged in the UK in September and helped generate the rapid rise in cases in December. We also know about the ‘South African’ variant (B.1.351), which appears to reduce the effectiveness of all vaccines to some degree. But these are just two of the better known variants, which seem to be emerging all the time (see also here).

COVID variants are the reason that so many countries have now severely restricted travel (‘almost closed borders’) into their countries in recent weeks. One of these variants could severely reduce the effectiveness of a country’s vaccination programme. It is likely that scientists would be able to change their vaccines to deal with these variants, but that will still mean at least another year before everyone is re-vaccinated and therefore means another year of lockdowns. We also do not know whether scientists could ever win a race between vaccine development and the ability of the virus to mutate.

Virus variants arise when there is a large amount of the virus about. One of the many failings of Western countries during this pandemic is to believe that you could safely vaccinate in an environment where domestic cases were high. That is exactly the environment that encourages mutations that are better at avoiding vaccines. If Western countries had followed an elimination strategy after the initial outbreaks in Spring last year, it would have been possible to keep borders open between these countries and the chances of producing a variant that can bypass vaccines within these countries would have been eliminated. In addition we would have had a small fraction of the deaths we have seen, with much less disruption to the economy.

Western countries now face a choice of how they handle COVID as vaccines are rolled out. Although no doubt reality will be far more complex than this, I think we can illustrate two types of outcomes available to them by thinking about two possible paths. I will call these two alternative paths ‘elimination’ and ‘living with COVID’. As with any attempt to look into the future, it assumes an existing technology that could change, and it involves some assessments that may prove wide of the mark (or maybe just wrong).

Elimination

This path tries to use a combination of almost closed borders, vaccination and other measures to enforce social distancing (including lockdowns) to get cases down to very low levels. At these very low levels, measures to enforce social distancing can be relaxed and an efficient test, trace and isolate (TTI) programme can keep R<1. During the summer, zero-COVID is achieved. The advantages of elimination are (see also here)

1. Once elimination is achieved, there is no chance that COVID variants that can bypass vaccines will emerge at home. While elimination is being achieved those chances are greatly reduced. This gives scientists a chance to develop new vaccines that can deal with known overseas variants while keeping everyone safe and COVID-free.
   
   

2. Countries that have achieved elimination can very easily open their borders to other countries that have done the same. Obviously this advantage is not that great if no other Western countries eliminate the virus.
   
   

3. Once elimination is achieved, the domestic economy can fully recover, there will be no more deaths from COVID, and there will be no more new cases of long COVID.

There is an important caveat to these three advantages. No ‘almost closed border’ is going to be foolproof, as both Australia and New Zealand have seen. When failure occurs, if TTI cannot eliminate the new cases, a short sharp lockdown is required to ensure the country returns to zero-COVID.

Living with COVID

This alternative arises when governments do not make any attempt at elimination, and two other outcomes prevail

1. Because of widespread vaccination together with TTI, countries can ensure R is very slightly below one in the summer months (If R is a lot less than one, elimination may occur naturally.)
   
   

2. However because COVID cases are still around by the end of summer, as winter approaches R increases to be above one, and cases increase. However because of vaccination cases never increase by enough to threaten health services, and once spring appears (or possibly before that) cases start to decrease again. (If cases rise in winter sufficiently to overwhelm the NHS, a further lockdown will be required.)
   
   

In this situation COVID becomes more like flu (it clearly isn’t like flu without vaccination), causing many deaths in winter but largely disappearing in summer. We learn to live with COVID.

Opening up borders now becomes a more messy affair. Countries would have to take informed guesses about whether other countries COVID cases were ‘safe’ (meaning they contained no dangerous variants) or not. However if most countries do not eliminate COVID, it will be easier to open borders to many countries than under elimination, once those countries have a similar number of cases that don’t include dangerous variants

There are two risks under this strategy. The positive risk is that vaccination turns out to be able to keep R<1 for most of the time, so COVID gradually dies out. This may happen because people feel more confident about being vaccinated as time goes on, and vaccines get better. Under this outcome, we don’t have to live with COVID for very long.

The negative risk is that during winter months when cases are high a mutation may develop that could bypass existing vaccines (partially or completely). This would be a very dangerous outcome, because it is likely to be some time before this variant is detected, by which time its numbers have multiplied substantially. (An advantage of the elimination strategy is that all outbreaks are treated as if they were dangerous, and are obviously much easier to see.) It is not clear to me how such a situation could be controlled without at least a year of lockdowns while new vaccines are developed and/or rolled out. The same danger arises from a failure in the ‘almost closed border’ that lets in a case with a COVID variant that can bypass vaccines.

Compared to the elimination strategy, there are two obvious advantages in living with COVID. The first is that lockdown can be relaxed or ended earlier. The second is that the country becomes less vulnerable to failures in its ‘almost closed borders’. The certain disadvantage compared to elimination is more deaths, and there is also the risk of allowing the development of variants that can bypass existing vaccines.

East versus West

At present the elimination strategy is being adopted by a group of countries which is small in number but does include China as well as Australia, New Zealand and Taiwan. There is no indication at the moment that any other countries are likely to join this group. It is also unclear whether these countries will continue with elimination once vaccination is widespread. They may be doing similar analysis to this (although no doubt better) to help them decide.

One prudent policy for the existing elimination countries is to wait and see how ‘living with the virus’ works out. If Western countries do learn to live with that strategy, the negative risks I point out above do not in practice occur, and they succeed in opening borders to each other at least, then there will be a strong incentive for the elimination countries to abandon that strategy. Equally, however, if it looks like Western countries are constantly playing catch-up with new domestically generated virus variants that bypass existing vaccines we may begin to see some Western countries begin to adopt elimination.

The UK government’s strategy for ending lockdown

Of the four criteria the UK government is going to use in deciding how quickly to ease its lockdown, steadily reducing cases is not among them. Instead we have “Infection rates do not risk a surge in hospital admissions” which is a much weaker criteria. It is actually exactly the criteria you would have under the ‘living with COVID’ strategy. It is therefore clear if unsurprising that the UK government has no intention of switching to an elimination strategy.

Much has been made of the government’s new step by step, data driven patient approach. What is less often said is that such an approach is essential to avoiding another resurgence in cases when most people have not yet been vaccinated. (Perhaps Tory MPs wanting to open everything quickly are only there to make the government look good?) Opening schools all at once in March is a risk. While it is good that secondary school children will be required to wear masks at all times, in France children aged six and over are told to do this. There is probably a lot more that could be done for schools in terms of ventilation, bubble sizes and so on. We also need to prepare for the possibility that schools going back may raise R to almost one, which would effectively invalidate the government's approach.

What is also not widely appreciated is that SAGE forecasts, like those released yesterday, are going to play a critical role in deciding how quickly lockdown is relaxed. Only in this context does the need to ensure “Infection rates do not risk a surge in hospital admissions” make sense. What SAGE needs to forecast is what level of cases in the summer, with lockdown at an end, is sufficient to ensure that the increase in cases over autumn and winter does not overwhelm the NHS. It is a very difficult forecast to make because we have no experience of what happens when most people are vaccinated, and if the government is wise it will base its calculations (on when to ease lockdown) on a worse case scenario. Unfortunately if it did that it would be acting out of character.

You also have to ask whether, if you intend to follow data rather than dates, it is wise to then announce a complete set of dates attached to a detailed list of the restrictions that will be lifted all the way to the end of lockdown? This gives a mixed message at the very least. In reality, given that we are far from clear how effective each element of the lockdown is, there may be a danger that the whole timetable is built on sand. But in political terms, this timetable is going to have a strong influence on expectations (where caveats are forgotten or just ignored by print media). The net result may be that disappointing those expectations will be a large political cost that politicians will not want to incur. A timetable this precise may have the effect of taking decisions away from the scientists when the data turns out to be worse than expected.