Beginning of 2021: The world had gone through a year of hardship and widespread public health measures to tackle COVID-19, including travel restrictions, quarantine, and blanket lockdowns. At last, a better understanding of how the virus transmits and how it affects health, testing capacity, and the availability of vaccines created the opportunity for a gradual return to (new) normality. COVID certificates – a digital tool to provide proof of vaccination, recovery, or a recent negative test – were introduced to replace blanket restrictions by targeted interventions. Among the first adopters, Israel and Denmark generalized the use of certificates to grant access to shops and restaurants, while the European Union considered their use to harmonize travel restrictions between member states.
COVID certificates posed many practical and ethical issues regarding discrimination, confidentiality, certification, improper application, and dissent. In an attempt to balance these considerations we argued for their adoption, but only on a temporary basis and while ensuring equitable access via free vaccination and testing. Overall, COVID certificates could help avoid renewed closures, and thus preserve individual freedoms and protect the economy. Social venues, we argued, should be classified into three risk categories dependent on the duration and intensity of the interactions, and COVID certificates deployed only when and where necessary (see Figure below, where the color of the zone relates to its current epidemiological situation).
By the end of May 2021, while the Delta variant was already causing great disruption in the UK, vaccine hesitancy and anti-vaccine sentiments were placing a route out of the pandemic at risk in many countries. In particular in France, where we are based, vaccine hesitancy is among the highest in Europe, and represents a major threat to the vaccination campaign. We thus elaborated on the additional incentives to get vaccinated created by COVID certificates, as suggested by a study in the Proceedings of the National Academy of Sciences. To increase overall vaccine uptake, and counter hesitancy, we proposed to the government a stepwise approach: First, adopt COVID certificates to reopen bars and discotheques (by then, these high-risk venues were closed for more than a year); second, in case of a resurgence, extend COVID certificates to all middle-risk venues such as restaurants, cafes, hospitality, public transport, etc.
Soon after, as the Delta variant started to take hold of France, President Macron announced the widespread adoption of COVID certificates on 12 July 2021 on public television. Many other major European countries followed suit, introducing similar measures around the same time. Notably, Italy announced the use of COVID certificates on 22 July and Germany on 10 August. While the immediate effect of COVID certificates on vaccine uptake appeared evident, its quantification and broader impact required rigorous analysis.
In our recent article in Nature Communications we estimated the effect of COVID certificates on vaccine uptake, health outcomes, and the economy, from their introduction to the end of 2021, for France, Germany, and Italy. To do so, we first constructed counterfactuals for vaccine uptake in each country – that is, the hypothetical progression of vaccination campaigns in these countries absent the introduction of COVID certificates – by using an innovation diffusion model. That is, a micro-founded behavioral model that was introduced by social scientists in the 1960s, and which has since served to study how new ideas and technologies spread, in particular the spread of medical innovations such as vaccines.
The estimated additional vaccine uptake varied across the three countries, likely because of different timing, vaccination hesitancy, and implementation rules (e.g., regional versus national adoption. On the day of their respective announcements, 54% of the population was vaccinated (i.e. had received at least one dose of a COVID-19 vaccine) in France, 63% in Germany, and 62% in Italy.; by the end of 2021, vaccination had risen to 78%, 74%, and 80%, respectively. How much of this increase can be attributed to COVID certificates? A substantial share: 13.0 (95% confidence interval: 9.7–14.9) percentage points (p.p.) for France, 6.2 (2.6–6.9) p.p. for Germany, and 9.7 (5.4–12.3) p.p. (See Figure below). An alternative statistical method (i.e., synthetic control), as well as an age-stratified model were used to validate the robustness of our findings.
How much did this additional vaccine uptake protect the population’s health and the economy? Regarding the former, we estimate the number of hospital and intensive care unit admissions, and deaths that were averted as a direct consequence of this policy intervention. The effect is most sizeable for France: Severe health outcomes would have been more than 30% higher without COVID certificates, entailing pressure on ICUs similar to that which prompted previous lockdowns. In Italy and Germany, the impact on severe outcomes was respectively 15% and 5%. Overall, the intervention saved around 6500 lives in these three countries in 2021.
Regarding the impact of COVID certificates on the economy, we conducted a quantitative analysis based on the weekly gross domestic product (GDP) estimates provided by the Organisation for Economic Co-operation and Development’s Weekly Tracker, developed by one of our coauthors. We found COVID certificates spur economic recovery as more people resume in-person economic activities, including working on-site and consuming goods and services; further, the avoidance of renewed closures contributes to the recovery. From their adoption to the end of 2021, COVID certificates averted weekly GDP losses of 0.6 (0.5–0.9) % in France, 0.3 (0.1–0.4) % in Germany, and 0.5 (0.3–0.7) % in Italy, accounting overall to additional €6 billion GDP in France, €1.4 billion in Germany, and €2.1 billion in Italy during the second half of 2021.
As the topic of COVID certificates has been actively debated, our study contributed to public discourse. For example, the French Ministers of Economics and Health commented on it, and international media including the Financial Times, Die Zeit, and La Repubblica covered our findings. Despite our and others research, population-wide non-pharmaceutical interventions remain contentious, hence the necessity of conducting holistic evaluations that capture their broad socio-economic short- and mid-term consequences. The COVID-19 pandemic has confirmed the central role of science, scientific knowledge, and research to provide guidance to decision makers. However, urgency inevitably led to partial analyses, favoring voices from certain disciplines to the detriment of others. In a recent expert consultation at the European Centre for Disease Prevention and Control (ECDC) our contribution centered around how to deal with uncertainty when a new health threat arises. Building on the lessons learnt during this pandemic, we believe that it is important to design emergency response plans that are flexible, rapidly implementable, and that can be adapted to diverse socio-economic and political contexts. The temporary and measured use of certification to prove health status or immunity should be considered as an effective tool to tackle future outbreaks.