I’ve been harboring hope lockdown might produce herd immunity through milder illness via milder viral “dose.”
That is to say, even under lockdown many of us will still be exposed to COVID-19, but we’ll be exposed to less of it than we would have been if, as in my case, we’d carried on living with a spouse taking the subway 5 days a week.
Ed read this article earlier today: Sortie de confinement, ou la somme de tous les dangers par Philippe Sansonetti.
Tells me that toward the end the author reports that herd immunity (l’immunité de groupe) to COVID-19 is by no means assured:
Les sujets guéris sont-ils protégés naturellement contre l’infection, qu’ils aient ou non développé ces fameux anticorps spécifiques neutralisants dont on espère tant ? A fortiori, les sujets demeurés asymptomatiques ou pauci-symptomatiques sont-ils protégés et pour combien de temps ? En effet le virus sera demeuré dans ce cas circonscrit à la muqueuse rhinopharyngée, ce qui peut donner lieu à une immunité locale, mais de quelle durée ? De quelle efficacité protectrice ? De quelle capacité à faire transition vers une immunité systémique globalement efficace ? En un mot, l’immunité de groupe offerte par beaucoup de maladies infectieuses et par les vaccins répondra-t-elle aux équations habituelles ?
Google translation: Are the healed subjects naturally protected against infection, whether or not they have developed these famous specific neutralizing antibodies which we so much hope for? A fortiori, are the subjects who remain asymptomatic or pauci-symptomatic protected and for how long? Indeed the virus will have remained in this case circumscribed to the nasopharyngeal mucosa, which can give rise to local immunity, but for how long? How protective is it? What is the ability to transition to globally effective systemic immunity? In a word, will the group immunity offered by many infectious diseases and vaccines meet the usual equations?
Looks like a good opportunity to practice my French.
I’m looking at the article I posted a couple of days ago: Public health interventions and epidemic intensity during the 1918 influenza pandemic.
I don’t have the bandwidth to read Hatchett et al closely at the moment … but wanted to clarify that their study does not offer a great deal of hope that we could develop herd immunity via more people infected with milder illness, thus fewer deaths. (It’s the study of immunity in Gangelt Municipality that supports herd-immunity-via-lower-viral-dose/lower-death.)
The authors assume the opposite, in fact:
Models can include viral doses (see Methods of modelling viral disease dynamics across the within- and between-host scales: the impact of virus dose on host population immunity) but you need more information about how the viral load changes with the course of the infection and how contagious people are at different stages. We don’t have that detailed information about SARS-CoV-2, so simpler models have to be used (and we don’t even have all the data we need to set the parameters of even simpler models, which is one reason the predictions have such wide ranges of possible outcomes).
And see:
Know your enemy
Can lockdown produce herd immunity with fewer deaths?
Social distancing and immunity
gasstationwithoutpumps on viral load and COVID-19 models
Social distancing and the 2nd wave
Viral dose, viral load
First time I’ve seen a researcher suggest we could achieve milder illness and immunity via lockdown:
By adhering to strict hygiene measures it is to be expected that the virus concentration of an infected individual can be reduced to the point that the illness manifests more mildly, with simultaneous development of an immunity. These favourable conditions are not present in a superspreading event (e.g. Karneval meeting, apres-ski bar in Ischgl, Austria). Hygienic measures are expected to have positive effects on overall mortality.
Preliminary result and conclusions of the COVID-19 case cluster study (Gangelt Municipality)
And see:
Know your enemy
Can lockdown produce herd immunity with fewer deaths?
Social distancing and immunity
gasstationwithoutpumps on viral load and COVID-19 models
Social distancing and the 2nd wave
Viral dose, viral load
I had no idea that viruses, like poisons, are more dangerous at higher doses.
Higher exposure, higher danger.
Lower exposure, lower danger:
Catherine & Katharine 