  COVID-19 abatement strategies have risks and uncertainties which could lead
to repeating waves of infection. We show -- as proof of concept grounded on
rigorous mathematical evidence -- that periodic, high-frequency alternation of
into, and out-of, lockdown effectively mitigates second-wave effects, while
allowing continued, albeit reduced, economic activity. Periodicity confers (i)
predictability, which is essential for economic sustainability, and (ii)
robustness, since lockdown periods are not activated by uncertain measurements
over short time scales. In turn -- while not eliminating the virus -- this fast
switching policy is sustainable over time, and it mitigates the infection until
a vaccine or treatment becomes available, while alleviating the social costs
associated with long lockdowns. Typically, the policy might be in the form of
1-day of work followed by 6-days of lockdown every week (or perhaps 2 days
working, 5 days off) and it can be modified at a slow-rate based on
measurements filtered over longer time scales. Our results highlight the
potential efficacy of high frequency switching interventions in post lockdown
mitigation. All code is available on Github
(https://github.com/V4p1d/FPSP_Covid19). A software tool has also been
developed so that interested parties can explore the proof-of-concept system.
