Attitudes towards booster, testing and isolation, and their impact on COVID-19 response in winter 2022/2023 in France, Belgium, and Italy: a cross-sectional survey and modelling study

Background:

European countries are focusing on testing, isolation, and boosting strategies to counter the 2022/2023
winter surge due to SARS-CoV-2 Omicron subvariants. However, widespread pandemic fatigue and limited
compliance potentially undermine mitigation efforts.

Methods:

To establish a baseline for interventions, we ran a multicountry survey to assess respondents’ willingness to
receive booster vaccination and comply with testing and isolation mandates. Integrating survey and estimated immunity data in a branching process epidemic spreading model, we evaluated the effectiveness and costs of current
protocols in France, Belgium, and Italy to manage the winter wave.

Findings:

The vast majority of survey participants (N = 4594) was willing to adhere to testing (>91%) and rapid isolation
(>88%) across the three countries. Pronounced differences emerged in the declared senior adherence to booster
vaccination (73% in France, 94% in Belgium, 86% in Italy). Epidemic model results estimate that testing and isolation
protocols would confer significant benefit in reducing transmission (17–24% reduction, from R = 1.6 to R = 1.3 in
France and Belgium, to R = 1.2 in Italy) with declared adherence. Achieving a mitigating level similar to the French
protocol, the Belgian protocol would require 35% fewer tests (from 1 test to 0.65 test per infected person) and avoid
the long isolation periods of the Italian protocol (average of 6 days vs. 11). A cost barrier to test would significantly
decrease adherence in France and Belgium, undermining protocols’ effectiveness.

Interpretation:

Simpler mandates for isolation may increase awareness and actual compliance, reducing testing costs,
without compromising mitigation. High booster vaccination uptake remains key for the control of the winter wave

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