Checchi, F., & Roberts, L. (2005). Interpreting and using mortality data in humanitarian emergencies. Humanitarian Practice Network, 52.
We have calculated P-scores from the raw weekly death data from the Human Mortality Database in the following way:
The Human Mortality Database has data for England & Wales (and Scotland) but not for the UK as a whole. England & Wales compose ~89% of the UK population. Source: UK ONS Population estimates for the UK, England and Wales, Scotland and Northern Ireland: mid-2019.
The positivity rate is often thought of in terms of the share of tests that yield a positive result. Our way of calculating the rate here is slightly different. It is calculated as the number of confirmed cases (i.e. people with a positive result) divided by either the number of people tested, or by the number of tests performed. These differ because people may be tested more than once. Countries vary in which test count they report. For details for individual countries see our detailed source descriptions.
At the WHO media briefing on 30 March, Dr Michael Ryan expressed this in terms of the positivity rate (the inverse of the number of tests per case):
“…In general where testing has been done fairly extensively we’ve seen somewhere between 3 and 12% of tests being positive… we would certainly like to see countries testing at the level of ten negative tests to one positive as a general benchmark of a system that’s doing enough testing to pick up all cases.“
The WHO provide a transcript of the media briefing.
Walker, P. G. T., Whittaker, C., Watson, O. J., Baguelin, M., Winskill, P., Hamlet, A., Djafaara, B. A., Cucunubá, Z., Mesa, D. O., Green, W., Thompson, H., Nayagam, S., Ainslie, K. E. C., Bhatia, S., Bhatt, S., Boonyasiri, A., Boyd, O., Brazeau, N. F., Cattarino, L., … Ghani, A. C. (2020). The impact of COVID-19 and strategies for mitigation and suppression in low- and middle-income countries. Science. https://doi.org/10.1126/science.abc0035
The definitions here are found in Walker et al. (2020); cited previously.
See Mathur, P. (2011). Hand hygiene: Back to the basics of infection control. The Indian Journal of Medical Research, 134(5), 611–620. https://doi.org/10.4103/0971-5916.90985 See also the WHO’s Coronavirus disease (COVID-19) advice for the public or the CDC’s How to Protect Yourself & Others or the NHS advice on COVID-19. And for a well-referenced summary of current scientific knowledge: Mohammed, Manal (2020). Coronavirus: Not all hand sanitisers work against it – here’s what you should use. The Conversation. Retrieved June 12, 2020.
Coronavirus envelope protein: Current knowledge | Virology Journal | Full Text. (n.d.). Retrieved June 17, 2020, from https://virologyj.biomedcentral.com/articles/10.1186/s12985-019-1182-0
Ferris Jabr (2020, March 13) – Why Soap Works. The New York Times. https://www.nytimes.com/2020/03/13/health/soap-coronavirus-handwashing-germs.html
Kwok, Y. L. A., Gralton, J., & McLaws, M.-L. (2015). Face touching: A frequent habit that has implications for hand hygiene. American Journal of Infection Control, 43(2), 112–114. https://doi.org/10.1016/j.ajic.2014.10.015
According to the CDC recommendations
See the CDC ‘How COVID-19 Spreads‘, the ECDC ‘Q&A on COVID-19‘, and the WHO ‘Q&A on COVID-19‘
Chu, Derek K; Elie A Akl, Stephanie Duda, Karla Solo, Sally Yaacoub, Prof Holger J Schünemann, et al. (2020) – Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. In The Lancet; June 01, 2020. DOI:https://doi.org/10.1016/S0140-6736(20)31142-9
Prather, K. A., Wang, C. C., Schooley, R. T. (2020) – Reducing transmission of SARS-CoV-2. In Science. https://doi.org/10.1126/science.abc6197
WHO (2020) – Advice on the use of masks in the context of COVID-19. Published 5 June 2020. Online here.
Personal NPIs [https://www.cdc.gov/nonpharmaceutical-interventions/personal/index.html]
CDC – Transmission of Measles.
NHS (2020) – Social distancing: what you need to do.
The WHO recommends that you “maintain at least 1 meter (3 feet) distance between yourself and others.”– WHO (2020) – Coronavirus disease (COVID-19) advice for the public. Accessed on June 17,2020.
NormileMay. 26, D., 2020, & Pm, 12:45. (2020, May 26). Japan ends its COVID-19 state of emergency. Science | AAAS. https://www.sciencemag.org/news/2020/05/japan-ends-its-covid-19-state-emergency
Where this threshold lies is not currently known. Current research however suggests that even the worst affected regions are not close to the immunity threshold.
See for example Lucy C Okell, Robert Verity, Oliver J Watson, Swapnil Mishra, Patrick Walker, Charlie Whittaker et al. (2020) – Have deaths from COVID-19 in Europe plateaued due to herd immunity? – The Lancet. Retrieved June 18, 2020, from https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31357-X/fulltext#sec1
It depends on several unknown parameters. It is possible that a share of the population already has some form of immunity – in this case this share of the population would already get us closer to the required threshold. And the key parameter is R0, which measures how many secondary infections we can expect from each infection. Several estimates for the threshold are quoted, one widely cited one is by Altmann et al. (2020) who write that “on the basis of this estimated R0, the herd immunity calculation suggests that at least 60% of the population would need to have protective immunity, either from natural infection or vaccination.” – Altmann, D. M., Douek, D. C., & Boyton, R. J. (2020). What policy makers need to know about COVID-19 protective immunity. The Lancet, 395(10236), 1527–1529. https://doi.org/10.1016/S0140-6736(20)30985-5
See also Randolph, H. E., & Barreiro, L. B. (2020). Herd Immunity: Understanding COVID-19. Immunity, 52(5), 737–741. https://doi.org/10.1016/j.immuni.2020.04.012
More detailed information is also made available by the authors.
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