In the first phase of the outbreak the priority was to limit the number of sick people such that the capacity of the health care system is not exceeded. COVID-19 can be a fatal disease even with very good health care, but in many cases sufficient health care can avoid fatalities.
With the help of restraints, in many regions the case rate has stabilized and the capacity of the health care system has increased such that probably few if any people are dying due to limitations of the health care system in those regions. On the other hand based on preliminary studies (e.g. for Santa Clara, USA, Netherlands) it appears only approx. 3% of the population have reached immunity (in the regions examined), such that without restraints every new case can bring us (almost) back to square one, with case numbers rising (almost) just as in the beginning. The studies also allow guessing a relationship between actual case rates and the reported case rates (the latter are highly dependent on the intensity of testing).
The restraints are in place and keep causing economic damage. So what could the policy be to lift the restraints?
1) Eradicate the disease completely through a strict world wide lock down without any possibly infectious human-to-human contacts. This is probably unrealistic and indeed it seems nobody is pursuing this approach.
2) A cybernetic approach of relax/measure/restrain. Restraints are fully lifted and as soon as case rates go up to capacity levels the most stringent restraints are put back into place. The major flaw with this approach is that it does not give businesses any type of certainty for planning (e.g. a restaurant owner stocking up on perishable supplies, just to learn that she is not allowed operating anymore).
3) An approach of very stringent restraint and near zero case rates until a vaccine is available. The earliest Phase II clinical trials of vaccines with sizeable numbers of participants are currently scheduled to end in December 2020 (this doesn't mean that the vaccine will be available to the general public by this time, even if the trial is successful). The problem I see with this approach is that it is somewhat arbitrary. What guideline is used to decide on the exact level of constraint? One technical justification could be that a near zero case rate may be easier to control than any other case rate. Another justification could be that the necessary measures for this approach have the same social and economic impact as the measures for an approach with a higher case rate.
4) Lastly I can imagine an approach which keeps case rates constant and close to but below health care system capacity and takes this as a guideline to relaxing the most economically damaging restraints as herd immunity builds up (or a vaccine becomes available). The graph below is the result of a simple simulation, which shows how the number of unprotected contacts can increase over time if the goal is to maintain a stable case rate. If the tolerable case rate can be increased due to improved health care system capacity the time of restraint could be significantly shortened. Depending on the tolerable case rate in about 7-15 months the number of unprotected contacts between people can double and in probably about 10-20 months a sufficient degree of immunity is reached such that restraints can be lifted almost completely.
COVID-19 will probably be on our minds for the next 10-20 months. Regions, which can tolerate and control higher case rates, could get through faster than regions which tolerate lower case rates, assuming recovering from the disease means immunity.
This doesn't mean that business activity has to stall during this time, but it does mean that serious measures to reduce infectious contacts (e.g. washing hands, face masks, distance keeping, working from home, broad testing/individual quarantines, contact tracing) have to be in place, which, however, can be continuously relaxed if the constant case rate approach is pursued. Many of those measures may not impact businesses very much at all, and it is important to chose those measures that have benefit in containing while minimizing impacts on business activity.
With the help of restraints, in many regions the case rate has stabilized and the capacity of the health care system has increased such that probably few if any people are dying due to limitations of the health care system in those regions. On the other hand based on preliminary studies (e.g. for Santa Clara, USA, Netherlands) it appears only approx. 3% of the population have reached immunity (in the regions examined), such that without restraints every new case can bring us (almost) back to square one, with case numbers rising (almost) just as in the beginning. The studies also allow guessing a relationship between actual case rates and the reported case rates (the latter are highly dependent on the intensity of testing).
The restraints are in place and keep causing economic damage. So what could the policy be to lift the restraints?
1) Eradicate the disease completely through a strict world wide lock down without any possibly infectious human-to-human contacts. This is probably unrealistic and indeed it seems nobody is pursuing this approach.
2) A cybernetic approach of relax/measure/restrain. Restraints are fully lifted and as soon as case rates go up to capacity levels the most stringent restraints are put back into place. The major flaw with this approach is that it does not give businesses any type of certainty for planning (e.g. a restaurant owner stocking up on perishable supplies, just to learn that she is not allowed operating anymore).
3) An approach of very stringent restraint and near zero case rates until a vaccine is available. The earliest Phase II clinical trials of vaccines with sizeable numbers of participants are currently scheduled to end in December 2020 (this doesn't mean that the vaccine will be available to the general public by this time, even if the trial is successful). The problem I see with this approach is that it is somewhat arbitrary. What guideline is used to decide on the exact level of constraint? One technical justification could be that a near zero case rate may be easier to control than any other case rate. Another justification could be that the necessary measures for this approach have the same social and economic impact as the measures for an approach with a higher case rate.
4) Lastly I can imagine an approach which keeps case rates constant and close to but below health care system capacity and takes this as a guideline to relaxing the most economically damaging restraints as herd immunity builds up (or a vaccine becomes available). The graph below is the result of a simple simulation, which shows how the number of unprotected contacts can increase over time if the goal is to maintain a stable case rate. If the tolerable case rate can be increased due to improved health care system capacity the time of restraint could be significantly shortened. Depending on the tolerable case rate in about 7-15 months the number of unprotected contacts between people can double and in probably about 10-20 months a sufficient degree of immunity is reached such that restraints can be lifted almost completely.
COVID-19 will probably be on our minds for the next 10-20 months. Regions, which can tolerate and control higher case rates, could get through faster than regions which tolerate lower case rates, assuming recovering from the disease means immunity.
This doesn't mean that business activity has to stall during this time, but it does mean that serious measures to reduce infectious contacts (e.g. washing hands, face masks, distance keeping, working from home, broad testing/individual quarantines, contact tracing) have to be in place, which, however, can be continuously relaxed if the constant case rate approach is pursued. Many of those measures may not impact businesses very much at all, and it is important to chose those measures that have benefit in containing while minimizing impacts on business activity.
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| Permissible contacts over time assuming a constant actual case rate. The lower case rate is 1000 actual cases per million population per day. The higher case rate is 2000 actual cases per million population per day.The case rate is the actual rate of cases, which according to initial studies, may vary by a significant factor from the reported case rate, depending on the intensity of testing being done (factor 50-85 Santa Clara, USA study, factor 18 Netherlands study). Permissible unprotected contacts is the number of potentially infectious contacts a person can have with an immune or not immune person in order to maintain the case rate. There is 3% immunity in the beginning of month 0. All this assumes an infected person is immune after recovery from the disease. |