The latest antibody study from Bergamo is particularly significant i believe to our understanding of Covid. Tests between late April and early June of a representative sample of the population showed 57% had antibodies.
www.google.co.uk/amp/s/amp.dw.com/en/coronavirus-tests-show-half-of-people-in-italys-bergamo-have-antibodies/a-53739727
This is very significant for a number of reasons:
A) Assuming antibodies provide protection, Bergamo was trending towards herd immunity, though given the severity of the Italian lockdown, it seems highly unlikely that it actually achieved it. Without intervention, as many will be infected in the “way down” and on the “way up” and, even with a high R, it would take a few weeks on the way down to approach herd immunity. As there wasn’t a delay of weeks between Bergamo reaching crisis point and lockdown occurring, there is very likely to be a gap between the number actually infected, and the higher number who would have been infected had the outbreak been allowed to peter out naturally. This indicates two important things:
I) the herd immunity percentage likely to be closer to 80% - possibly even higher - than the 60% figure that was mooted in the early days
ii) natural immunity that is able to fight off infection without antibody production is less prevalent than had been hoped, perhaps very low. This doesn’t mean necessarily that many people don’t have decent natural or t-cell protection that could fight off low infectious doses of Covid, but that this wouldn’t necessarily be enough to provide solid immunity alone in an uncontrolled and unmitigated outbreak with high quantities of virus circulating.
B) Bergamo is the probably only place that Covid has “ripped through“ without any intervention. For the poor people of Bergamo, they have provided probably the only case study of the effects of Covid spread across a pristine population without any intervention (whether imposed or population-led) until the majority had been infected. It is therefore the only place where a reliable like-with-like IFR/CFR comparison with flu can be made. In all other places, interventions occurred before, generally well before, this point, having a significant impact on the infection’s trajectory.
A similar study was done with the result published in late April.... Given the time taken to do the study, improved test reliability, and the time for antibodies to appear, it’s not surprising that there’s been a leap from the 35% figure back then.
www.google.co.uk/amp/s/www.euronews.com/amp/2020/04/28/coronavirus-more-than-a-third-of-people-in-italy-s-covid-19-epicentre-estimated-to-have-ha
This paper published that 6,000 of Bergamo’s 1.1m had died with Covid at that point. I’ve read that Italy’s Covid death toll could be significantly understated (Ie 6,000 could be too low) but I won’t get into that here and now. Although I couldn’t find any more recent data for Bergamo, Italy’s reported deaths have increased from 27,000 to 34,000 since the date of that article, an increase of
26%. Taking the conservative assumption that deaths in Bergamo would have risen by half this amount (as it was the start of the epidemic in Italy and therefore would have been ahead of the death curve), I’ve estimated Bergamo’s Covid deaths at 6,800... This is 0.62% of the population and would
be the low bound figure for IFR/CFR (assuming they are the same for the purposes of this), with this rising to 0.87% if 80% infections are required for herd immunity.
Apply that to the UK, and you get 582,000 deaths in a no intervention scenario... Round down a bit to take account for Italy having a slightly higher age profile than the UK, and, his personal hypocrisy aside, Prof. Ferguson’s 510,000 estimated reasonable worst case scenario looks pretty good and has stood the test of time!