COVID-19 Vaccination Uptake Around Saudi Arabia's 2021 Vaccination Requirement for Access to Public and Private Establishments: An Interrupted Time-Series and Synthetic Control Analysis

Abstract

Background: On 18 May 2021, Saudi Arabia announced that, from 1 August 2021, proof of COVID-19 vaccination in the Tawakkalna application would be required to enter government and private establishments, educational institutions, events and public transport. We estimated how vaccine uptake changed around the announcement and enforcement of this requirement.

Methods: Quasi-experimental study of national weekly data (3 January to 30 October 2021; 43 weeks) from Our World in Data, with policy timing from the Oxford COVID-19 Government Response Tracker. Segmented regression with autocorrelation-robust errors modelled weekly doses per 100 population with interruptions at announcement and enforcement. A synthetic control built from 47 countries without mandatory-vaccination codes in the policy tracker estimated the gap in cumulative primary-series doses per 100 population (primary estimand), with placebo-in-space, in-time placebo, negative-control and timing-shift analyses.

Results: Mean weekly doses per 100 population rose from 1.64 before the announcement to 3.84 between announcement and enforcement, peaking at 7.51 in the first enforcement week; second doses accounted for most of the July increase. The weekly trend steepened after the announcement (slope 0.41 versus 0.21 doses per 100 per week) and reversed after enforcement (slope change −0.87 (95% CI −1.18 to −0.56)). By 30 October 2021, Saudi Arabia had administered 14.0 more cumulative doses per 100 population than its synthetic control (125.4 versus 111.4), but this gap was not unusual relative to placebo countries (permutation p = 0.60), was −4.2 at enforcement, and varied in sign across sensitivity analyses.

Conclusions: Vaccination activity in Saudi Arabia accelerated between the announcement and the enforcement of the vaccination requirement, mainly through completion of second doses. Comparison with a synthetic counterfactual did not provide robust evidence of additional cumulative uptake attributable to the policy, and the result depends on assumptions that the falsification tests only partly supported.

Keywords

• COVID-19 vaccines
• vaccination mandate
• interrupted time series
• synthetic control
• health policy
• Saudi Arabia