There is often a clear distinction between a strategy designed to (a) eliminate a virus/ the spread of disease quickly, and (b) manage the spread of infection over the long term (see The overall narrative).
However, generally, the language of virus management is confusing. We need to be careful with interpreting the language used in these minutes, and other sources such as oral evidence to House of Commons committees, particularly when comparing the language at the beginning (when people were also unsure what to call SARS-CoV-2 and COVID-19) to present day debates.
For example, in January, it is tempting to contrast ‘slow down the spread of the outbreak domestically’ (28.1.20: 2) with a strategy towards ‘extinction’, but the proposed actions may be the same even if the expectations of impact are different. Some people interpret these differences as indicative of a profoundly different approach (delay versus eradicate); some describe the semantic differences as semantics.
By February, SAGE’s expectation is of an inevitable epidemic and inability to contain COVID-19, prompting it to describe the inevitable series of stages:
‘Priorities will shift during a potential outbreak from containment and isolation on to delay and, finally, to case management … When there is sustained transmission in the UK, contact tracing will no longer be useful’ (18.2.20: 1; its discussion on 20.2.20: 2 also concludes that ‘individual cases could already have been missed – including individuals advised that they are not infectious’).
Mitigation versus suppression
On the face of it, it looks like there is a major difference in the ways on which (a) the Imperial College COVID-19 Response Team and (b) SAGE describe possible policy responses. The Imperial paper makes a distinction between mitigation and suppression:
- Its ‘mitigation strategy scenarios’ highlight the relative effects of partly-voluntary measures on mortality and demand for ‘critical care beds’ in hospitals: (voluntary) ‘case isolation in the home’ (people with symptoms stay at home for 7 days), ‘voluntary home quarantine’ (all members of the household stay at home for 14 days if one member has symptoms), (government enforced) ‘social distancing of those over 70’ or ‘social distancing of entire population’ (while still going to work, school or University), and closure of most schools and universities. It omits ‘stopping mass gatherings’ because ‘the contact-time at such events is relatively small compared to the time spent at home, in schools or workplaces and in other community locations such as bars and restaurants’ (2020a: 8). Assuming 70-75% compliance, it describes the combination of ‘case isolation, home quarantine and social distancing of those aged over 70’ as the most impactful, but predicts that ‘mitigation is unlikely to be a viable option without overwhelming healthcare systems’ (2020a: 8-10). These measures would only ‘reduce peak critical care demand by two-thirds and halve the number of deaths’ (to approximately 250,000).
- Its ‘suppression strategy scenarios’ describe what it would take to reduce the rate of infection (R) from the estimated 2.0-2.6 to 1 or below (in other words, the game-changing point at which one person would infect no more than one other person) and reduce ‘critical care requirements’ to manageable levels. It predicts that a combination of four options – ‘case isolation’, ‘social distancing of the entire population’ (the measure with the largest impact), ‘household quarantine’ and ‘school and university closure’ – would reduce critical care demand from its peak ‘approximately 3 weeks after the interventions are introduced’, and contribute to a range of 5,600-48,000 deaths over two years (depending on the current R and the ‘trigger’ for action in relation to the number of occupied critical care beds) (2020a: 13-14).
In comparison, the SAGE meeting paper (26.2.20b: 1-3), produced 2-3 weeks earlier, pretty much assumes away the possible distinction between mitigation versus suppression measures (which Vallance has described as semantic rather than substantive – scroll down to The distinction between mitigation and suppression measures). In other words, it assumes ‘high levels of compliance over long periods of time’ (26.2.20b: 1). As such, we can interpret SAGE’s discussion as (a) requiring high levels of compliance for these measures to work (the equivalent of Imperial’s description of suppression), while (b) not describing how to use (more or less voluntary versus impositional) government policy to secure compliance. In comparison, Imperial equates suppression with the relatively-short-term measures associated with China and South Korea (while noting uncertainty about how to maintain such measures until a vaccine is produced).
One reason for SAGE to assume compliance in its scenario building is to focus on the contribution of each measure, generally taking place over 13 weeks, to delaying the peak of infection (while stating that ‘It will likely not be feasible to provide estimates of the effectiveness of individual control measures, just the overall effectiveness of them all’, 26.2.20b: 1), while taking into account their behavioural implications (26.2.20b: 2-3).
- School closures could contribute to a 3-week delay, especially if combined with FE/ HE closures (but with an unequal impact on ‘Those in lower socio-economic groups … more reliant on free school meals or unable to rearrange work to provide childcare’).
- Home isolation (65% of symptomatic cases stay at home for 7 days) could contribute to a 2-3 week delay (and is the ‘Easiest measure to explain and justify to the public’).
- ‘Voluntary household quarantine’ (all member of the household isolate for 14 days) would have a similar effect – assuming 50% compliance – but with far more implications for behavioural public policy:
‘Resistance & non-compliance will be greater if impacts of this policy are inequitable. For those on low incomes, loss of income means inability to pay for food, heating, lighting, internet. This can be addressed by guaranteeing supplies during quarantine periods.
Variable compliance, due to variable capacity to comply, may lead to dissatisfaction.
Ensuring supplies flow to households is essential. A desire to help among the wider community (e.g. taking on chores, delivering supplies) could be encouraged and scaffolded to support quarantined households.
There is a risk of stigma, so ‘voluntary quarantine’ should be portrayed as an act of altruistic civic duty’.
- ‘Social distancing’ (‘enacted early’), in which people restrict themselves to essential activity (work and school) could produce a 3-5 week delay (and likely to be supported in relation to mass leisure events, albeit less so when work activities involve a lot of contact.
[Note that it is not until May that it addresses this issue of feasibility directly (and, even then, it does not distinguish between technical and political feasibility: ‘It was noted that a useful addition to control measures SAGE considers (in addition to scientific uncertainty) would be the feasibility of monitoring/ enforcement’ (7.5.20: 3)]
As theme 2 suggests, there is a growing recognition that these measures should have been introduced by early March (such as via the Coronavirus Act 2020 not passed until 25.3.20), and likely would if the UK government and SAGE had more information (or interpreted its information in a different way). However, by mid-March, SAGE expresses a mixture of (a) growing urgency, but also (b) the need to stick to the plan, to reduce the peak and avoid a second peak of infection). On 13th March, it states:
‘There are no strong scientific grounds to hasten or delay implementation of either household isolation or social distancing of the elderly or the vulnerable in order to manage the epidemiological curve compared to previous advice. However, there will be some minor gains from going early and potentially useful reinforcement of the importance of taking personal action if symptomatic. Household isolation is modelled to have the biggest effect of the three interventions currently planned, but with some risks. SAGE therefore thinks there is scientific evidence to support household isolation being implemented as soon as practically possible’ (13.3.20: 1)
‘SAGE further agreed that one purpose of behavioural and social interventions is to enable the NHS to meet demand and therefore reduce indirect mortality and morbidity. There is a risk that current proposed measures (individual and household isolation and social distancing) will not reduce demand enough: they may need to be coupled with more intensive actions to enable the NHS to cope, whether regionally or nationally’ (13.3.20: 2)
On 16th March, it states:
‘On the basis of accumulating data, including on NHS critical care capacity, the advice from SAGE has changed regarding the speed of implementation of additional interventions. SAGE advises that there is clear evidence to support additional social distancing measures be introduced as soon as possible’ (16.3.20: 1)
Overall, we can conclude two things about the language of intervention:
- There is now a clear difference between the ways in which SAGE and its critics describe policy: to manage an inevitably long-term epidemic, versus to try to eliminate it within national borders.
- There is a less clear difference between terms such as suppress and mitigate, largely because SAGE focused primarily on a comparison of different measures (and their combination) rather than the question of compliance.
See also: There is no ‘herd immunity strategy’, which argues that this focus on each intervention was lost in radio and TV interviews with Vallance.