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.

Original Article

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