3. Defining the policy problem: ‘herd immunity’, long term management, and the containability of COVID-19

Frankly, the widespread and intense focus on ‘herd immunity’ was a needless distraction, sparked initially by government advisors but then nitrous-turbo-boosted, gold-plated, and covered in neon lights during a series of ridiculous media and social media representations of ill-worded statements.

This initial focus took attention away from a much more profound discussion of what the UK government thinks is feasible, which informs a very stark choice: to define the COVID-19 problem as (a) a short term pandemic to be eradicated (as in countries like South Korea) or (b) a long term pandemic to be expected and managed every year (the definition in countries like the UK).

There is no ‘herd immunity strategy’

The key thing to note is that ministers and their advisors:

  • Did talk in general terms about the idea of ‘herd immunity’ in March (best summed up as: herd immunity is only possible if there is a vaccine or enough people are infected and recover)
  • Did not recommend an extreme non-intervention policy in which most of the population would be infected quickly to achieve herd immunity (in February, advisers described this outcome as the Reasonable Worst Case Scenario; see also Whitty, 5.3.20: q15-17)

Rather, describing the idea of herd immunity as an inevitability (not determined by choice) is key to understanding the UK approach. It helps us question the idea that there was a big policy U-turn in mid-March. Policy did change in the short term, but a sole focus on the short term distracts from the profound implications of its long-term strategy (in the absence of a vaccine) associated with phrases such as ‘flatten the curve’ (rather than ‘eradicate the virus’).

Examples of UK government representatives talking about herd immunity

1.      Wilful misrepresentation, often put to music

Full Fact’s challenge to the wilful misrepresentation of Prime Minister Boris Johnson’s appearance on the ITV programme This Morning (10.3.20): Here is the transcript of what Boris Johnson said on This Morning about the new coronavirus

These video stinkers, in which people (a) cut quotes so that you don’t hear the context, and provide a misleading headline, or (b) put a bunch of cut interviews in sequence and combine them with a tune that sounds like a knock-off version of the end credits to the TV Series The Hulk (in other words, people design these messages to get an emotional reaction).

2.      Headlines stoking the idea of herd immunity during a time when everyone should have been careful about how explain and interpret early discussions

British government wants UK to acquire coronavirus ‘herd immunity’, writes Robert Peston (12.3.20)

3.      The accentuation of a message not being emphasised by government spokespeople, at the expense of a message that requires more attention.

This interview is described by Sky News (13.3.20) as: ‘The government’s chief scientific adviser Sir Patrick Vallance has told Sky News that about 60% of people will need to become infected with coronavirus in order for the UK to enjoy “herd immunity”’. You might be forgiven for thinking that he was on Sky extolling the virtues of a strategy to that end. This was certainly the write-up in respected papers like the FT (UK’s chief scientific adviser defends ‘herd immunity’ strategy for coronavirus). Yet, he was saying nothing of the sort. Rather, when prompted, he discussed herd immunity in relation to the belief that COVID-19 will endure long enough to become as common as seasonal flu.

See Vallance’s interview on the same day (13.3.20) during Radio 4’s Today programme (transcribed by the Spectator and headlined as “How ‘herd immunity’ can help fight coronavirus” as if it is his main message). The Today Programme also tweeted only 30 seconds to single out that brief exchange. Yet, clearly his overall message – in this and other interviews – was that some interventions (e.g. staying at home; self-isolating with symptoms) would have bigger effects than others (e.g. school closures; prohibiting mass gatherings) during the ‘flattening of the peak’ strategy (‘What we don’t want is everybody to end up getting it in a short period of time so that we swamp and overwhelm NHS services’). Rather than describing ‘herd immunity’ as a strategy, he is really describing how to deal with its inevitability.

[PAC: Note that these examples are increasingly difficult to track, because people take the herd immunity argument for granted or cite reference to it misleadingly. For example, Scalley et al state “To widespread criticism, he floated an approach to “build up some degree of herd immunity” founded on an erroneous view that the vast majority of cases would be mild, like influenza”. Their citation takes you here, in which there is no reference to herd immunity or the quotation]

In oral evidence, Vallance (17.3.20: q70) compares these measures as follows (while describing the ‘confidence intervals’ as ‘quite wide’, q77):

‘The interventions we have made have all been modelled out – it is just modelling; we need to be aware of that – to say what effect they would have on the peak. In the first one we introduced, case isolation, you would expect to bring the peak down by about 20%. In the second one, whole household quarantine, you would expect to bring it down by about 25%. The social shielding of the elderly has less of an effect on the peak but a much bigger effect on the mortality, where you might expect it to be between 20% and 30%. General social distancing measures—as you said, quite extreme ones have now been introduced—would be expected to reduce the peak by about 50%. They are not necessarily all completely additive, but it tells you that together we should expect those to have a very significant effect on the peak, and we should start to see the rates come down in two or three weeks’ time. The ambition in any outbreak is to try to get the R0 value down below one. That is the value, on average, of what one person would do in infecting others. At the moment, the R0 value is somewhere between two and three, and the aim is to get it below one, at which time things start to decrease’

Further discussion of herd immunity in oral evidence

Throughout the evidence sessions, some MPs raise the herd immunity idea, but not energetically, and perhaps largely to allow government advisers to clarify their initial statements (e.g. 17.3.20: q112; 17.4.20: q303).

In May, Vallance (5.5.20: q389 and q404) makes it extra-clear that he was not advocating the ‘herd immunity’ idea associated with no intervention:

‘Q389 Chair: It sounds like there is still a degree of uncertainty as to whether an antibody leads to an immune response. Back on 13 March, you said the aim was to build up some kind of herd immunity where lots of people in the country had had the virus so that they could not catch it again. When you said that, which was nearly two months ago, what was your evidence then for the existence of that kind of immunity?

Sir Patrick Vallance: I should be clear about what I was trying to say, and, if I did not say it clearly enough, I apologise. What I was trying to say was that, in the absence of a therapeutic, the way in which you can stop a community becoming susceptible to this is through immunity. Immunity can be obtained either by vaccination or by people who have had the infection. We don’t know, as I said, exactly what degree of protection you get from natural infection, and we don’t yet have a vaccine. The second thing is that the higher the proportion of people in the community with immunity, the easier it is to control the disease and, ultimately, the easier it is to release measures. So vaccination becomes an important part of how you end up with protection, assuming you can get a decent immune response with vaccines, which we also do not know yet, but you would expect there to be some degree of immunity. The expectation is that antibody responses will correlate with immunity to some degree—maybe very high or maybe not so high. As to the degree of protection, whether it is to reduce the severity of the disease or to reduce the overall effect of the disease and the ability to catch the disease, we still have some work to do to find out about that.

Q404 ‘To reiterate, as I said at the beginning to Jeremy Hunt, my points about immunity were not actually about getting immunity through that route. My point has been clear from the outset that we need to suppress the peak, and keep the peak down flat below the level at which the NHS can cope, to protect the NHS and to make sure that we reduce deaths. That has been the strategy.’

See also:

Government emails on herd immunity

[Update 15.10.20] The BBC used a Freedom of Information request to secure ‘every email sent by Sir Patrick [Vallance] and chief medical officer for England, Professor Chris Whitty, from the start of February to the start of June, containing the words “herd immunity”‘.

The BBC narrative is that some people think that the government was in favour of pursuing ‘herd immunity’ via high infection rates in the population (60%) that would contribute to hundreds of thousands of deaths.

For me, this is a misleading story.

The emails largely show that these advisors regret ever using the term ‘herd immunity’ because it allows people to jump to wild conclusions based on patching together minimal evidence (and ignoring more convincing evidence that advisors pushed strongly for suppression measures).

Defining the COVID-19 problem in the UK

If so, this clarity allows us to think more about the implications of the UK government’s problem definition. In a much larger paper (that’s right – its completion is on the to-do list), I suggest that these elements inform the UK government’s definition of the policy problem by mid-March 2020:

  1. We are responding to an epidemic that cannot be eradicated. Herd immunity is only possible if there is a vaccine or enough people are infected and recover.
  2. We need to use a suppression strategy to reduce infection enough to avoid overwhelming health service capacity, and shield the people most vulnerable to major illness or death caused by COVID-19, to minimize deaths during at least one peak of infection.
  3. We need to maintain suppression for a period of time that is difficult to predict, subject to compliance levels that are difficult to predict and monitor.
  4. We need to avoid panicking the public in the lead up to suppression, avoid too-draconian enforcement, and maintain wide public trust in the government.
  5. We need to avoid (a) excessive and (b) insufficient suppression measures, either of which could contribute to a second wave of the epidemic of the same magnitude as the first.
  6. We need to transition safely from suppression measures to foster economic activity, find safe ways for people to return to work and education, and reinstate the full use of NHS capacity for non-COVID-19 illness. In the absence of a vaccine, this strategy will likely involve social distancing and (voluntary) track-and-trace measures to isolate people with COVID-19.
  7. Any action or inaction has a profoundly unequal impact on social groups.

In other words, UK government policy is about reducing or moving the initial peak of infection, followed by longer term management to ensure that the NHS always has capacity to treat. The short-term focus emphasized the need to get the timing right in relation to the balance between public health benefits and social and economic cost (rather than to adopt a precautionary principle):

‘There is also timing. There will be quite a long period between knowing that we have an epidemic running at a reasonable rate and the actual peak. We are keen not to intervene until the point when we absolutely have to, so as to minimise the economic and social disruption on people, and then to stop it again as soon as we can afterwards. It is both the combination of what we need to do—in later questions we might want to go into some details about the things we can do—and the timing. The timing is critical. It is important that we minimise the social disruption while doing what we can to make sure we maximise the public health impact’ (Whitty, 5.3.20: q18)

[See also q39 on the unresolved difficulties of isolating vulnerable people physically without producing too high costs socially, and

q59 on ‘no need at this stage to be stocking up on anything. … this is going to be a marathon not a sprint. This is going to be a long period. There is going to be a lead time before the serious take-off of this comes, which we will be able to indicate … There is nothing in the current environment that would rationally lead someone to want to go out and stock up on stuff’.]

It is difficult to tell exactly what ministers and advisors expect to happen long-term in the absence of a vaccine (although Vallance 17.3.20: q102 is clear that the initial suppression measures will take an indeterminate number of months, not a few weeks). For example, are they managing infections and expecting regular deaths (assuming a mortality rate at approximately 1%) or expecting a high NHS capacity to reduce that mortality rate? Most discussions in public refer generally to the peak and NHS capacity but not the specifics:

‘Overall, the goal is clearly to bend the curve down and to make sure that the NHS capacity is there, and at the same time to do the work to try to improve our ability as a society to cope with this disease, with the goal of lifting some of the incredibly restrictive methods that we have had to place on the population in order to get the disease under control’ (Hancock, 17.4.20: q306)

The long-term implications of ‘flatten the curve’

In that context, Costello (17.4.20: q303) sums up my niggling concerns about the ‘flatten the curve’ message. This phrase suggests that we

  • keep transmission low enough to make sure that the number of relevant cases does not overwhelm the NHS (an approach with high support), and
  • accept that transmission will remain at a lower but significant rate until a vaccine is found (an approach that is not discussed as much, but it implies the continuation of deaths at a lower but regular rate):

‘The recent estimates, even from the chief scientific officer, are that after this wave, where we could see 40,000 deaths by the time it is over, we could have maybe only 10% to 15% of the population infected or covered, so the idea of herd immunity would mean maybe another five or six more waves to get to 60%. I do not think we should be using phrases such as “flatten the curve” because it implies continuing. We have to suppress this right down.’ (Costello, 17.4.20: q303)

The other side of this coin is that government advisers were initially working on the assumption that they could keep the initial number of deaths to 20000, which suggests a population infection rate well below 10% of the population (2/60m people, assuming the 1% mortality rate described by Whitty, 5.3.20: q11) and no expectation of herd immunity in the short term.

Comparing the UK definition with approaches in South Korea and China

The oral evidence sessions, probing the UK government’s longer term vision, help make key aspects of this definition somewhat clearer in two main ways.

First, they help confirm that UK policy is built on the assumption that COVID-19 will be a regular or seasonal problem (in the absence of a vaccine and culture change). For example, Hunt (17.3.20: q105) suggests that some country leaders think there will be (a) a peak of infection, then (b) containment, followed by (c) fizzling out:

‘China has officially announced that it thinks it is past the peak. The South Korean Foreign Minister was on TV at the weekend saying that she thinks South Korea has passed the peak, and it seems to think it has passed the peak with less than 1% of the population being infected. It is very realistic that there could be second or third waves, but it does not seem to be expecting it as much as you do … The Chinese and Korean view seems to be that it could be something like SARS, for example, which just burns itself out when the reproduction rate gets below one. Why is it that you are, unfortunately, so certain that it will come back?’

In contrast, Vallance (e.g. 17.3.20: q104-5) suggests strongly that COVID-19’s properties indicate high transmissibility and continuous recurrence (we may have to plan for a ‘spike every year’). This definition of the problem underpins the UK government’s expectation of long term management and, I think, is one of several reasons that ministers and advisers describe evaluation as premature.

Second, they suggest that this approach is built on a further assumption of what it feasible in the UK in relation to social behaviour.

A key element of international comparison relates to very different assumptions about social behaviour in each country. For example, the committee heard from respondents about experiences in South Korea, Hong Kong, Taiwan, and Singapore, in which previous pandemics – such as SARS – had a profound effect on government preparation and public behaviour (e.g. Comas-Herrera, 19.5.20: q446; Lum (Professor of Social Work and Social Administration, Hong Kong University) 19.5.20: q450, 456, 463; Chen (Former Vice-President of the Republic of China (Taiwan), 3.6.20: 492-504).

As a result, in many countries, you can expect widespread mask use and routine temperature checks, relatively invasive test and tracing measures, and obligatory isolation, to form part of a government’s response (such as to act quickly on regional ‘hotspots’ to prevent nationwide spread; compare with Hancock, 17.4.20: q318 on the connection of a UK lockdown to national unity, and Vallance, 5.5.20: q410-11 lukewarm on regional approaches, but also Harries, 5.5.20; q416 on the UK addressing hotspots in the earliest phase).

All of these measures and behaviours can contain the transmission of coronavirus in a way that seems to be far less feasible in the UK. For example, Doyle (26.3.20: q199-202) suggests that the South Korean system involves a degree of personal invasion not expected in UK, including giving bank details to government and being tested in public places like restaurants.

Further, even if these measures are possible, there is scepticism about their long-term impact: ‘the Chinese state and people are still doing some pretty extraordinary things’, with the potential that ‘when they take their foot off the brake the epidemic will surge back again’ (Whitty, 5.3.20: q13-4).

Instead, the emphasis from UK government respondents is initially (from March) about recommending the measures with the highest positive public health impact and lowest negative social and economic impact (handwashing). For example, Whitty (5.3.20: q18, see also q25, and Vallance 17.3.20: q92) compares measures:

‘ranging from those with almost no economic impact and high efficacy – top of the range being washing your hands and second being covering your mouth with a tissue when you cough – all the way down to those that have major societal impact, such as closing schools, which obviously affects children but also parents, potentially employment and particular sectors of the economy. It is very easy to choose a package of measures that is quite dramatic but has relatively little impact on the epidemic. We are very keen to avoid that, so we are modelling out all the combinations that we can because people’s livelihoods depend on it’.

Throughout, there is an emphasis on what might work in a UK-style liberal democracy characterised by relatively low social regulation, reinforced with reference to behavioural public policy:

‘All the behavioural science would suggest that we have to get the transparency right. We have to get the communication right. We have to trust that people want to know things, they want to know about this and they want to be able to be empowered to make their own decisions’ (Vallance, 17.3.20: 98).

COVID-19 policy in the UK: oral evidence to the Health and Social Care Committee (5th March- 3rd June 2020)

  1. The need to ramp up testing (for many purposes)
  2. The inadequate supply of personal protective equipment (PPE)
  3. Defining the policy problem: ‘herd immunity’, long term management, and the containability of COVID-19
  4. Uncertainty and hesitancy during initial UK coronavirus responses
  5. Confusion about the language of intervention and stages of intervention
  6. The relationship between science, science advice, and policy
  7. Lower profile changes to policy and practice
  8. Race, ethnicity, and the social determinants of health


Filed under COVID-19

11 responses to “3. Defining the policy problem: ‘herd immunity’, long term management, and the containability of COVID-19

  1. Pingback: 2. The inadequate supply of personal protective equipment (PPE) | Paul Cairney: Politics & Public Policy

  2. Pingback: COVID-19 policy in the UK: oral evidence to the Health and Social Care Committee (5th March- 3rd June 2020) | Paul Cairney: Politics & Public Policy

  3. Pingback: 4. Uncertainty and hesitancy during initial UK coronavirus responses | Paul Cairney: Politics & Public Policy

  4. Pingback: 5. Confusion about the language of intervention and stages of intervention | Paul Cairney: Politics & Public Policy

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