Jose Lorenco, Robert Paton, Mahan Ghafari, Moritz Kraemer, Craig Thompson, Peter Simmonds, Paul Klenerman, Sunetra Gupta
Date: 25 March, 2020
- Three phases of the spread of a novel pathogenic infectious agent:
- Slow accumulation of new cases (often undetectable).
- Rapid growth in cases of infection, disease and death.
- Slowdown of transmission due to depletion of susceptible individuals (termination of first wave).
- This typical progression assumes:
- No control measures (social distancing, travel bans, etc.).
- The infection elicits a protective immunity.
- Susceptible-Infected-Recovered model (SIR).
- Explore sensitivity of the system to fraction of population vulnerable to disease and death.
- Means: explore what level of the population has already been infected and is now immune:
- Higher number of people currently immune -> lower number of people vulnerable to future infection (herd immunity).
- Lower the number of vulnerable people -> less people may require hospitalization.
- Current wave of the COVID-19 epidemic should last 2-3 months.
- Infections may have started up to 1 month before first death occurred (UK, Italy).
- If that is true, the current number of infections may be far higher than estimated.
- Perhaps as high as half of the population.
- The vast majority of infections develop very mild or no symptoms at all.
- Fewer than 1 in 1,000 infected require hospitalization.
- May already have a substantial level of herd immunity in both countries.
- Urgent need to for testing to understand actual level of immunity.
- Understand what stage of the epidemic we are in.
- Confirms the importance of understanding who has already been infected (and how long immunity lasts, etc.).
- Many people that contract the disease are without symptoms.
- So without proper testing, we don’t know.
- The study has not yet been formally published or peer-reviewed.
- Criticism of the study argues that its assumptions may not be in line with some real world data:
- For instance, the Lombardy region in Italy is well beyond 1 in 1,000 people infected requiring hospitalization.
- In fact, 1 in 1,000 of its entire population required hospitalization (with a death rate is 0.42 per 1,000 people)