Excerpts from a recent social media post:
It is important to understand the difference between Case Fatality Rate (CFR) and Infection Fatality Rate (IFR). IFR is the figure we need to focus on. A comprehensive Stanford University study showed that, across 51 locations, the median COVID-19 IFR was 0.2%. This shows very clearly that the IFR for Covid-19 in NZ is about the same as the flu (0.1%). See the published paper at: Ioannidis JPA. Infection fatality rate of COVID-19 inferred from seroprevalence data. Bull World Health Organ. 2021;99(1):19-33F. doi:10.2471/BLT.20.265892
We have always thought up to yesterday that the number of people infected with COVID-19 in New Zealand and worldwide was usually only slightly higher than the number of cases (except maybe at the start of an outbreak).
It is well known that people may be infectious and spread COVID-19 a few days before they are symptomatic.
We assumed that these people would become cases within a few days (before/after) of becoming symptomatic. Contact tracing/testing could find cases before they were symptomatic.
Currently the world CFR = 2% (5m out of 250m is 1 in 50). A few days ago:
Let’s suppose that IFR = 0.2%
(If IFR = 0.1 in NZ then the factor 10 below would become 20 especially in point 6).
- CFR = 10 x IFR since CFR = 2 and IFR = 0.2.
- Infections = 10 x Cases. i.e. Cases = 10% of infections.
- R0 is far bigger than expected using case numbers since we have to include 10 times as many infections.
- From paper linked to on PANDA website:
Data Synthesis Twenty-three seroprevalence surveys representing 14 countries were included. Across all countries, the median IFR in community-dwelling elderly and elderly overall was 2.4%.
i.e. IFR = 2.4%. CFR = 24%. See:
- World cases = 250,000,000. Infections = 2,500,000,000.
- In NZ Cases = 8.1K. Infections=162K?
- Since 90% of infections are never identified as cases, 90% of infections must be essentially asymptomatic(?)
- We need to assume that all infections will spread COVID-19.
We conducted a poll:
https://www.neighbourly.co.nz/public/auckland/titirangi/message/67152996 (only local members can vote)
For the best answer in the poll and an update for this post please see: