Basic estimation-prediction techniques for Covid-19, and a prediction for Stockholm

Tom Britton

Another important observation is that in the first three scenarios, the final fraction infected exceeds the critical immunity level v C = 1 − 1/R 0 = 0.6 [4] . This implies that in these three situations the community has reached herd immunity and is hence protected from additional outbreaks when preventive measures are relaxed (assuming infection induce complete immunity!). For the two latter scenarios, a new doubling time of d E = 14 days and the situation where preventive measures give R E = 0.80, the final fraction infected is even smaller which of course is positive. However, since the corresponding fractions lie below herd immunity, the community is at risk for additional outbreaks if all preventive measures are relaxed. This is particularly the case for the last scenario where less than 20% are infected during the first outbreak.