Shall I mention herd immunity?
Approximately 90-95% of the population needs to be infected with COVID-19 before herd immunity is achieved. China, Germany and Italy have been mass testing in feverent hope of this happening. Their have been the obvious set backs – lack of testing kits for one, and then the logistical issues; not being able to do the number of daily tests needed to capture the 60 million – 1.4 billion strong population in these countries (realistically speaking this would take years rather than months). There is also speculation whether exposure in fact means immunity, with reports of second positives being reported on a monthly basis.
Scientifically speaking in the absence of herd immunity, isolation procedures or lock down must continue. A resurgence in the number of death rates to speed up this process is a highly unlikely proposition. Every politician out there would therefore be looking at ways to make this more palatable to their constituents. My local library that belongs to a consortium of libraries in the UK called the ‘Idea Store’ is a good litmus test when it comes to such matters. At the start of lockdown, my book loans were automatically renewed till the end of April, but as of today this has been extended to July 1st. I could have sworn that the current dictum is lockdown for a further three weeks.
As the NY Times says in its opinion piece, this is lockdown with no clear exit strategy: https://www.nytimes.com/2020/04/16/world/europe/uk-coronavirus-lockdown-exit.html.
Maybe they all missed this seminal paper in the Science Magazine on the exit strategy:
The bottom line is that intermittent or prolonged periods of social distancing/lockdown may be needed to mitigate the resurrgence of infection. They base their conclusions on the following principles:
- ‘After the initial pandemic wave, SARS-CoV-2 might follow its closest genetic relative, SARS-CoV-1, and be eradicated by intensive public health measures after causing a brief but intense epidemic’ – this scenario is considered unlikely.
- ‘Alternatively, the transmission of SARS-CoV-2 could resemble that of pandemic influenza by circulating seasonally after causing an initial global wave of infection’.
‘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‘
So what are our potential outlooks?
One-time social distancing scenarios in the absence of seasonality.
One-time social distancing scenarios with seasonal transmission.
Intermittent social distancing scenarios with current and expanded critical care capacity.
It’s a toss up between which strategy each nation would ultimately choose. My question is whether vulnerable individuals, including those on immunosuppressants should isolate into early Oct or April the following year based on the above assumptions of one time isolation or intermittent social distancing?
What do you think?