Posted by probability > 2020-08-15 18:17 | Report Abuse

https://www.forbes.com/sites/robertpearl/2020/08/10/coronavirus-vaccine-gone-wrong/#7ae7db87ae4d


4. The vaccine gets approved but might be only 50% effective

That brings us to the novel coronavirus. In April, the WHO noted the ideal vaccine would establish immunity in at least 70 percent of the population, including the elderly. In July, an FDA official added, “We’re going to need a vaccine that’s probably in the order of 70% effective and 70%, at least, of the population is going to need to take it.” Meanwhile, Dr. Fauci is on the record as saying that he, too, would settle for a 70% to 75% effective vaccine.

But those are all “ideal” situations. =FDA guidance issued in June stated, “To ensure that a widely deployed COVID-19 vaccine is effective, the primary efficacy endpoint point estimate for a placebo-controlled efficacy trial should be at least 50%.”

This possibility leads to some disheartening mathematics. Assuming that only 50% of the population takes a vaccine that is only 50% effective, the nation’s immunization rate could be as low as 25%. That total would be insufficient to end the pandemic.

Achieving herd immunity, the point at which the virus would no longer spread, would require at least 70% of the country (200 million Americans) to either be vaccinated or acquire the virus and recover from it. Further, that estimate assumes long-lasting immunity from the virus.

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From above, if we U.S is to achieve herd immunity, 70% has to be immune.

If vaccine efficacy is 60% and 70% are vaccinated by end 2021 ( i doubt that fast), immunity level of U.S :

= 0.60 x 0.70
= 0.42 or 42%

At 42% immunity, looking at current cases of 60k per day with restrictions / safety measure, the cases per day at minimum will still be about 20k per day coupled with relaxation of rules.

Thats 5 x times higher than China at its peak

Further there is risk of immunity fading in 6 months...