(3) The Impact of COVID Passport Mandates on The Number of Cases of and Hospitalizations With COVID-19 in the UK: A Difference-In-Differences Analysis

Saturday, August 27, 2022

8:00 AM – 6:00 PM CEST

Location: Hall C

Publication Number: 677

Presenting Author(s)

Kim López Güell
– DPhil candidate, NDORMS, University of Oxford, Oxford, United Kingdom

Co-Author(s)

Albert Prats-Uribe, MPH, MD
– CSM, NDORMS, University of Oxford, United Kingdom
Martí Català
– Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK, United Kingdom
Daniel Prieto-Alhambra, MD, MSc, PhD, FISPE
– Professor of Pharmaco- and Device Epidemiology, CSM, NDORMS, University of Oxford, University of Oxford, Oxford, United Kingdom
Clara Prats
– Associate professor, Physics Department. Universitat Politècnica de Catalunya, Castelldefels (Barcelona), Catalonia, Spain
Jotun Hein
– Professor, University of Oxford, Oxford, United Kingdom

Background: There is evidence that COVID passport mandates can, under certain circumstances, result in an increase in the uptake of SARS-CoV-2 vaccination. However, evidence is lacking on their impact on COVID-19 cases and related hospitalization.

Objectives: We aimed to measure the impact of COVID passport mandates on the incidence of detected SARS-CoV-2 infections and hospitalizations with COVID-19 in the UK during the Autumn of 2021.

Methods: Official data on COVID-19 cases and admissions over Autumn 2021 were obtained from the UK COVID-19 dashboard (https://coronavirus.data.gov.uk/), stratified by country.
Incidence rates per 100,000 were estimated using official denominators (Office of National Statistics). Rates from Northern Ireland, Scotland, and Wales were considered as three separate interventions, with different dates as per official date of mandate publication/s. Data from England was used as the counterfactual, as no passport mandates were imposed until late December.
The first analysis was performed on the 7-day smoothed data using Negative Binomial Segmented Regression (NBSR). ARIMA models were also fit to control for potential association of the observations. England data was used as a counterfactual for Difference in differences (DID) models.

Results: Covid Passports led to a decrease in the incidence of cases and hospital admissions in Northern Ireland, as well as in Wales during the second half of November. The same was seen for hospital admissions in Wales and Scotland during October. In Wales the incidence rate of cases in October already had a decreasing tendency, as well as in England, hence a particular impact of Covid Passport was less obvious. Method assumptions for the Difference-in-Differences analysis did not hold for Scotland. Additional NBSR and ARIMA models suggest similar results.

Conclusions: Mandatory Covid Passports reduced COVID-19 transmission and hospitalizations when Delta predominated in the UK, but lost efficacy when Omicron became the most common variant.