View Single Post
  #12  
Old 03-20-2020, 06:24 PM
DSeid's Avatar
DSeid is online now
Guest
 
Join Date: Sep 2001
Location: Chicago, IL
Posts: 23,954
This paper, first shared here by bump in this thread is very important to get some sense of what is out there relative to the concept and what might be required as the "now what?".

First the limitations of the paper - they used just one set of possible assumptions, including that children were just as contagious as adults (and the best current evidence is that they surprisingly are much less so); and they assumed that the asymptomatically infected are 2/3s as contagious as those with symptoms, while more recent data suggests that it is more like half as contagious.

But still.

It is being cited as very sobering because by that model all of what they would call "mitigation", slowing but not stopping the spread, results in overwhelming healthcare system capacity 8-fold.

They are concluding that the goal has to be suppression:
Quote:
Given that mitigation is unlikely to be a viable option without overwhelming healthcare systems,
suppression is likely necessary in countries able to implement the intensive controls required. Our
projections show that to be able to reduce R to close to 1 or below, a combination of case isolation,
social distancing of the entire population and either household quarantine or school and university
closure are required (Figure 3, Table 4). Measures are assumed to be in place for a 5-month duration.
Not accounting for the potential adverse effect on ICU capacity due to absenteeism, school and
university closure is predicted to be more effective in achieving suppression than household
quarantine. All four interventions combined are predicted to have the largest effect on transmission.
Problem though. Do that combination of all for just 5 months and you suppress cases numbers to below surge capacity but when you release it, well after 5 to 6 weeks you explode again, as bad as before. (Which happens to coincide with influenza season starting up again. )
Quote:
The more successful a strategy is at temporary suppression, the larger the later epidemic is predicted to be in the absence of vaccination, due to lesser build-up of herd immunity.
Which was exactly the OP's point.

Alternatively you can hold the suppressive measures in place for the 18 months that it takes to get a vaccine to market. OR try doing that with
Quote:
an adaptive policy in which social distancing (plus school and university closure, if used) is only initiated after weekly confirmed case incidence in ICU patients (a group of patients highly likely to be tested) exceeds a certain “on” threshold, and is relaxed when ICU case incidence falls below a certain “off” threshold (Figure 4). Case-based policies of home isolation of symptomatic cases and household quarantine (if adopted) are continued throughout.
The suppressive level interventions would be expected to be in place on for 2/3s of the 18 months period with "holidays" a third of the time.

For mitigation they found that cancelling mass gatherings did extremely little. Isolation at home of symptomatic cases for 7 days with voluntary quarantine of household contacts for 14 days (assuming 50% compliance), and social distancing of the over 70 crowd, was the least poorly effective approach, and did better than suppression with release after 5 months.

So under the assumptions of the model (using current case fatality rates, assuming children are as infective as adults, and that the asymptomatic are 2/3s as contagious as the symptomatic), the "now what?" is a very long very haul or having it with a surge delayed but not decreased.

Under those assumptions.