Thread by @vipintukur

A new modelling study on the value of vaccine boosters to mitigate the global impact of #Omicron

By fitting an immunological model to population-level vaccine effectiveness (VE) data, NAb titres for Omicron are reduced by 3.9 fold compared to the Delta variant 1/

Under this model, it is predicted that 90 days after boosting with the Pfizer-BioNTech vaccine, efficacy against severe disease (admission to hospital) declines to 95.9% against the Delta & 78.8% against the Omicron 2/

Integrating this immunological model within a model of SARS2 transmission, the size of the Omicron wave will depend on the degree of past exposure to infection across the population, w/ relatively small Omicron waves in countries that previously experienced a large Delta wave 3/

Booster doses can have a major impact in mitigating the epidemic peak, although in many settings it remains possible that healthcare capacity could still be challenged. 4/

This is particularly the case in #ZeroCovid countries where there is little prior infection-induced immunity and therefore epidemic peaks will be higher. 5/

Where dose supply is limited, targeting boosters to the highest risk groups to ensure continued high protection in the face of waning immunity is of greater benefit than giving these doses as primary vaccination to younger age-groups. 6/

In many settings it is likely that health systems will be stretched, and it may therefore be necessary to maintain and/or reintroduce some level of NPIs to mitigate the worst impacts of the Omicron as it replaces the Delta variant. 7/

medrxiv.org/content/10.110…