Debunking the Immunity Debt Theory
Examine the idea of "Immunity Debt" and the logic behind it, and how the Swedish pandemic response allows for debunking this theory. Learn why bigger (and earlier) seasonal waves of infections are expected after circulation of an endemic bug has been transiently suppressed.
Prof Francois Balloux
Director @UGI_at_UCL. Interest in Infectious disease epidemiology, pathogen genomics and global health Mastodon account: @FBalloux@genomic.social
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It is rarely a good idea to base strong claims on anecdotal, simplistic and poorly understood factoids. Let's have a look at this claim that the Swedish pandemic response allows debunking that "flawed immunity debt theory".
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
1/ https://t.co/cJRToAenEk -
The idea of "Immunity debt" is that bigger (and earlier) seasonal waves of infections are expected after circulation of an endemic bug has been transiently suppressed. The logic is that people exposed to a seasonal virus gain transient protection from re-infection to it.
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
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Was circulation of RSV reduced in the early phases of the pandemic in Sweden?
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
Yes, indeed, there was very little RSV in circulation in 19/20, and hardly any in 20/21. This was followed by two big out-of-sink peaks in 21/22 and 22/23.
3/https://t.co/TActeczHyh pic.twitter.com/WRJcjU2VNV -
Contrary to what some may believe, Sweden took pandemic mitigation measures, including some drastic ones (ie. longer secondary school closures than several other European countries). The difference was that the implementation relied largely on persuasion rather than coercion.
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
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Contact rates (particularly indoors) were down in Sweden during the early stages of the pandemic, more so actually than in many other places. This is expected to have reduced circulation of seasonal endemic viruses (eg. RSV or influenza), and hence immunisation to them.
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
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Circulation of seasonal viruses is highly complex. There are other forces at play including 'global migration' in particular between the two hemispheres, and probably also interference between viruses. But we don't have to invoke those to realise this claim is without merit.
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023
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To be fair, to the best of my knowledge, Swedish authorities also didn't insist that people follow totally bonkers, performative measures such as "not sitting on a park bench" or "masking toddlers". Anyway ...
— Prof Francois Balloux (@BallouxFrancois) June 16, 2023