‘Herd Immunity’ Revisited: Thinking the Unthinkable?

On Monday 16th March a report was released from Imperial College London titled: ‘Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand.’ It came out literally 2 days after I had placed my piece regarding ‘Herd Immunity’ onto Medium. Had I of read it before then my piece would have been somewhat different as the report makes for very sobering reading and for very serious reflection upon the oncoming onslaught from a disease, which as a public health threat, is analogous to the 1918 H1N1 influenza pandemic (‘The Spanish Flu’).

We know that the current rate of infection from COVID-19 is more contagious than the ordinary influenza but is similar to the one that swept the globe a hundred years ago. Harvard University epidemiologist Marc Lipsitch told a gathering of experts this weekend: ‘‘That is similar to pandemic flu of 1918, and it implies that the end of this epidemic is going to require nearly 50% of the population to be immune, either from a vaccine, which is not on the immediate horizon, or from natural infection.”

The more infectious a virus is, the more people need to be immune for us to achieve complete herd immunity. Measles, one of the most easily transmitted diseases with an R0 over 12, requires about 90% of people to be resistant for unprotected people to then become…