Covid Prevalence, Mortality Rate, Herd Immunity: Updated Estimates

In an April 24 post I extrapolated findings from a New York immunity study to estimate the US coronavirus prevalence at 3 percent and the mortality rate at 0.6 percent. Yesterday’s Euronews summarized new national immunity findings from two of the hardest-hit countries.

On Wednesday, a study of 60,000 people was published by the Spanish government. It suggested only five per cent of the country’s population has been infected, so far. The results did vary massively across the country: Madrid has a prevalence rate of 11.3 per cent; but in provinces in the south, east and north-west of the country, the rate is much lower. In Seville, for example, 2.3 per cent of people have contracted COVID-19…

And in France, a study led by the Pasteur Institute says 4.4 per cent of France (2.8 million people) has been infected. Researchers say the rate even in the worst-hit parts of the country – in the east part and in and around Paris – is still only between nine and ten per cent on average. These same researchers go on to explain that “around 65 per cent of the population should be immune if we want to control the pandemic by the sole means of immunity”.

So, using Spain’s data:

  • population = 47 million
  • prevalence = 47 million x .05 = 2.35 million
  • corona deaths = 27.6 thousand
  • mortality rate = 27.6K/2.35M = 1.2%

…and for France:

  • population = 67 million
  • prevalence = 67 million x .044 = 2.95 million
  • corona deaths = 27.5 thousand
  • mortality rate = 27.5K/2.95M = 0.9%

Averaging across the two countries, around 1 percent of those who have contracted the virus have died from it — considerably higher than the earlier 0.6 percent from the New York data. Further extrapolating the Eurodata to the US:

  • population = 330 million
  • corona deaths = 88.9 thousand
  • prevalence = 88.9K/.01 = 8.89 million = 2.7% of the population

In order to achieve herd immunity, 330M people x .65 prevalence x .01 mortality rate = 2.15 million Americans will die of covid. So far 89 thousand — not quite 0.1 million — have died. We’ve got a long way to go…



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