How will people react if Covid-19 flares up when the lockdown ends?

[DSeid]

@ThelmaLou

According to this article, COVID infections/deaths will rise and fall over the next two to three years.

My bold.

At the link there are illustrations of the waves that represent these three scenarios.

Not sure why anyone has been, knowing what we now know, even considering anything other than those prospects being in the cards at all.

First comment - of the three prospects laid out in the Minnesota link there is ONE that is the worst, by FAR - that is the “Fall Peak” one … and one that is the least poor is the “Slow Burn”. Fall Peak not only has the largest peak (thus most able to exceed health system capacity) but is most likely to occur along with influenza. A double catastrophe. That would occur with Of the possibilities the one would most want to TRY to create is “Slow Burn” … which includes having some level of cases over summer, a controlled burn allowed that is not allowed to get too hot by the degrees of mitigation measures in place in various areas.

Second comment - critical inputs are still placeholder wild assed guesses. The Science link, more rigorous in its modeling, accepts that the very fundamentals are just not known.

The pandemic and post-pandemic transmission dynamics of SARS-CoV-2 will depend on factors including the degree of seasonal variation in transmission, the duration of immunity, and the degree of cross-immunity between SARS-CoV-2 and other coronaviruses, as well as the intensity and timing of control measures. …

Interesting that they are raising the issue of degrees of cross-immunity with other coronaviruses. Not something that gets mentioned too often. They continue -

The betacoronaviruses can induce immune responses against one another: SARS-CoV-1 infection can generate neutralizing antibodies against HCoV-OC43 (16) and HCoV-OC43 infection can generate cross-reactive antibodies against SARS-CoV-1 (17). While investigations into the spectrum of illness caused by SARS-CoV-2 are ongoing, recent evidence indicates the majority of cases experience mild to moderate illness with more limited occurrence of severe lower respiratory infection (18). Current COVID-19 case fatality rates are estimated to lie between 0.6% and 3.5% (19, 20), suggesting lower severity than SARS-CoV-1 and MERS but higher severity than HCoV-OC43 and HCoV-HKU1. The high infectiousness near the start of often mild symptoms makes SARS-CoV-2 considerably harder to control with case-based interventions such as intensive testing, isolation and tracing, compared to SARS-CoV-1 and MERS coronaviruses (21).

Then they go on to create some models that explore different scenarios of seasonal variation, cross-immunity, immunity duration, based off of various other placeholder assumptions.

A variety of possibilities result.

One would be “smaller peak incidence during the initial pandemic wave but larger recurrent wintertime outbreaks” with a lighter summer season. Again, the nightmare option, timed with influenza.

Another -

“If immunity to SARS-CoV-2 is permanent, the virus could disappear for five or more years after causing a major outbreak” … of note in that scenario some of the common cold causing HCoVs could go away too “if SARS-CoV-2 induced 70% cross immunity against them, which is the same estimated level of cross-immunity that HCoV-OC43 induces against HCoV-HKU1.”

Another -

"Even if SARS-CoV-2 immunity only lasts for two years, mild (30%) cross-immunity from HCoV-OC43 and HCoV-HKU1 could effectively eliminate the transmission of SARS-CoV-2 for up to three years before a resurgence in 2024, as long as SARS-CoV-2 does not fully die out "

They then modeled impacts of mitigation, both “one time” and “intermittent” under “the worst-case scenario” … that really needs to be emphasized, and is not mentioned in the NYT communication of the article.

They also modeled variation in efficacy of mitigation as well and come up with results that might surprise some.

longer and more stringent temporary social distancing did not always correlate with greater reductions in epidemic peak size. In the case of a 20-week period of social distancing with 60% reduction in R0, for example (Fig. 4D), the resurgence peak size was nearly the same as the peak size of the uncontrolled epidemic: the social distancing was so effective that virtually no population immunity was built. The greatest reductions in peak size come from social distancing intensity and duration that divide cases approximately equally between peaks

Let’s really highlight that, even as we fully acknowledge the limits of the worst case assumptions they use. Achieving greater and longer initial suppression would, in their model of intermittent suppression, lead to bigger peaks later.

From the discussion section:

if establishment occurs in the autumn when the reproduction number is rising, which could occur in countries that maintain epidemic control by contact tracing and quarantine through the summer, or if SARS-CoV-2 is not subject to the same summertime decline in transmissibility as HCoV-OC43 and HCoV-HKU1, then a high peak prevalence of infection is likely. One-time social distancing efforts may push the SARS-CoV-2 epidemic peak into the autumn, potentially exacerbating the load on critical care resources if there is increased wintertime transmissibility. Intermittent social distancing might maintain critical care demand within current thresholds, but widespread surveillance will be required to time the distancing measures correctly and avoid overshooting critical care capacity.

Let’s maybe consider broadening from “intermittent” to “dynamically adjusted and graduated mitigation measures chose for most efficacy over least harms as the data as collected informs.” Note also that they do allow that if cases become low enough that “aggressive contact tracing and quarantine” become practical (current per them not) it "could alleviate’ the needs.

Also from the discussion section:

Our findings indicate key data required to know how the current SARS-CoV-2 outbreak will unfold. Most crucially, serological studies could indicate the extent of population immunity, whether immunity wanes, and at what rate … if serological data reveals the existence of many undocumented asymptomatic infections that lead to immunity (50), less social distancing may be required. Serology could also indicate whether cross-immunity exists between SARS-CoV-2, HCoV-OC43, and HCoV-HKU1, which could affect the post-pandemic transmission of SARS-CoV-2. We anticipate that such cross-immunity would lessen the intensity of SARS-CoV-2 outbreaks … To implement intermittent social distancing, it will be necessary to carry out widespread viral testing for surveillance to monitor when the prevalence thresholds that trigger the beginning or end of distancing have been crossed. Without such surveillance, critical care bed availability might be used as a proxy for prevalence, but this metric is far from optimal … if there have been many undocumented immunizing infections, the herd immunity threshold may be reached sooner than our models suggest. …The model will have to be tailored to local conditions and updated as more accurate data become available. Longitudinal serological studies are urgently required to determine the extent and duration of immunity to SARS-CoV-2, and epidemiological surveillance should be maintained in the coming years to anticipate the possibility of resurgence.

The take away to my read -

IF one realistically believes with some surety and confidence that we will be able to get new infection rates very low and then be able to get enough people cooperating with testing and quarantining in an ongoing basis for an indefinite future then one should try to push down to near zero. Note not “should” but real world “will”.

The risk of trying for that and failing though is dramatic. That is the Fall Peak nightmare. Systems overrun with a high peak occurring timed with influenza.

If one is not sure of being able to accomplish that then a controlled slow burn (in their model achieved by intermittent social distancing) may be the least poor choice.

Again, my preferred variation is controlling it with “dynamically adjusted and graduated mitigation measures chose for most efficacy over least harms as the data as collected informs”, with special attention to doing MUCH better at protecting the most vulnerable than we have done do date.