Thread by @BertrandBio

Debate on potential for single dose in the UK. Which is aligned with a thought I previously shared. You cannot do it just like that but at least it deserves some second thoughts.

More data needed before giving just one vaccine dose, says Covid adviser theguardian.com/world/2020/dec…

There's also this mention of the rigid "by age" strategy for vaccination, which I agree with. After the most vulnerable and the 60-65+, I also thought at vaccinating the population of potential super-spreaders, i.e. 18-25y or 18-30y (or 16-25y/16-30y), then going downwards from

60-65y. In the medium term, I guess it would make more sense to do that than doing the 18-25/18-30y at the end.

Last week there was also this table in a preprint. I found it pretty discouraging, because to my understanding, these

Modelling of COVID-19 vaccination strategies and herd immunity, in scenarios of limited and full vaccine supply in NSW, Australia medrxiv.org/content/10.110…

calculations rely on the VE to prevent infection i.e. sterilizing immunity. But the VEs of vaccine we currently know indicate the ability to prevent symptomatic disease, and the picture is way less clear on prevention of infection. From the early data from $AZN eg on aymptomatic

cases, it seems their vaccine doesn't reach the same VE for prevention of infection vs prevention of symptomatic disease. So it would mean that we would have to discount the VE in this table (assumingly for prevention of transmission) wrt disclosed VEs (on prevention of

symptomatic disease) if one would actually want to predict the %age of people who would need to get their shot. Then, what would be this discount, this is the question. But when I see the low willingness to vaccinate against #COVID19 in France (44% last numbers), even with

pre-existing immunity (seroprevalence 15-20%? a bit higher?), I say to myself that the road to "herd immunity" will be long, very long. Silver lining: new infections are still supposed to decrease progressively even if the immunity level hasn't reached the "herd immunity"

theoretical level. At the same time, naturally acquired immunity through infection is also likely to vary way more than vaccination, both in quality and in length of protective immunity. So I hope the willingness to get vaccinated will progress upwards massively throughout 2021,

so that we eventually get out of this. Obviously, the data have to support a strongly positive benefit/risk ratio, and ideally with the lowest risk baseline as possible.