Domestic COVID certificates: what does the evidence say?

Born to help reopen international travel routes, digital COVID certificates are now required in several countries to enter premises such as bars, restaurants, gyms, pools, and museums, and to attend large public events. But do they work — and what for, precisely? More fundamentally, is it even possible to have an evidence-based debate about them at all? Tracing The Tracers looked at the lessons we should learn from the available literature, with the help of a stellar group of researchers.

Fabio Chiusi
Research Associate

As the world enters a second pandemic autumn, several countries now require digital proof of COVID-19 status to enter premises such as bars, restaurants, gyms, pools, and museums, and to attend large public events. However, a question remains: Do digital COVID certificates (DCCs) for domestic use—not for international travel, as originally conceived—actually work? And, what would it mean for a domestic DCC to “work”?

To address this question, AlgorithmWatch reviewed the available literature on immunity and vaccine passports—both in relation to COVID-19 and concerning its historical precedents—and also spoke to some of the most influential researchers in the field. While a consistent, evidence-based answer failed to emerge—we simply don’t have enough data, yet—some evidence and arguments appear to indicate shared concerns within the scientific community that are being overlooked or downplayed by governments that have adopted a DCC for domestic use.

This is all the more important as the debate—or lack thereof—around domestic DCCs fits into the larger context of emergency technological responses to the COVID-19 pandemic, which are often mired in controversy related to the lack of transparency and evidence and their scarce effectiveness. DCCs are no exception, adding to the impression that these responses are too often born out of a tech-solutionist ideological framework (according to which every social problem requires a technological fix) rather than resulting from careful consideration and sound scientific scrutiny.

As a result, a growing number of studies indicate that the actual contribution of domestic DCCs to the fight against COVID-19—both in terms of boosting vaccination rates and containing infections—could be more controversial than how governments who uncritically pushed for their adoption would like it to be. In fact, rushing their deployment might lead to increased polarization toward vaccine hesitancy and refusal in certain segments of the population, all the while only gaining marginal results among those who comply with the scheme.

Therefore, in this analysis, we will explore the domestic uses of DCCs, ask whether they are as effective as the national health authorities claim they are - and according to which criteria. We will also look for the best evidence-based answers to these questions that the literature provides at present.

In an emergency, decisions must be made - often before all options and solid evidence are available. However, this should not be an excuse to leave the deployment of new and potentially invasive public health tools to the whim of national governments. Only through an evidence-based discussion can we make a properly democratic use of domestic digital COVID certificates, and, therefore, ask whether it is possible to ground their justification in science and actual epidemiological needs, to transparently and unambiguously check and discuss the results they produce (and, therefore, how and when they should be discontinued), and ultimately to avoid emboldening extremists and vaccine deniers who see it as a tool of repression—rather than liberation—for mere, and mostly misguided, political reasons.

The normalization of health surveillance is indeed a valid concern when it comes to technological response to COVID-19. The researchers AlgorithmWatch talked to were eager to warn that this includes domestic uses of DCCs.

Suddenly, a plethora of domestic digital COVID certificates

In the context of COVID-19, the idea of a digital (and paper-based) proof of vaccination status (or whether a person has received a negative test result within the last 48/72 hours, or has recovered from the disease recently) started with the intention of safely reopening international travel routes in Europe and beyond.

As documented by Tracing The Tracers in a previous analysis, this initially meant that a plethora of solutions was developed by both public institutions and private entities, particularly by tech and travel companies. Then, the European Union stepped in and provided some guidance to member states with the EU “Digital COVID Certificate”.

Soon after, a similar tool was deployed in Israel— the so-called ‘Green Pass’—but with very different goals. The Green Pass — a term later adopted by France and Italy as well — is a digital COVID certificate that is required to take part in several social activities, such as, going to the gym, dining indoors, or attending leisure, sports, and cultural events.

Even though the Green Pass was controversial (and possibly ineffective, as we’ll see later, in more detail), Denmark decided to adapt the idea in April 2021, the United Arab Emirates followed in June, and, most importantly, French president Emmanuel Macron, introduced a similar pass in July and later gradually expanded its use to include other activities. The domestic French DCC system was arguably the most influential, as international media started considering the scheme as a role model for other countries to imitate.

And many did. For example, Italy immediately followed suit. Mario Draghi’s government adopted a step-by-step approach that ultimately led to an unprecedented ‘Super Green Pass which will be required for almost all social activities—including school and work— from 15 October.

Similar systems were then implemented in several other countries—both in Europe and elsewhere—although each country ended up tailoring the DCC to their requirements. Some DCCs require only one vaccine shot, others two—and soon possibly three (for some?), as in Israel, given that ‘booster’ shots are becoming a requirement in some countries. In some schemes, the validity of a negative test result lasts 48 hours, in others, it lasts 72 hours; some schemes offer free or cheap testing, others don’t or don’t anymore. Venues and activities for which a domestic DCC is required also vary from country to country, as do the criteria adopted for social distancing within them.

Slovakia developed its own unique system. Facility owners and event organizers use a state-developed app, ‘Overpass’, to enforce one of three entry options, according to The Slovak Spectator: "They can either let everybody in (including the untested and unvaccinated); require confirmation that participants have been fully vaccinated against Covid, tested negative for Covid or have recovered from Covid; or they can let only the fully vaccinated in.” Enforcement, which was so far limited to visual confirmation, will differ from region to region depending on the risk of infection.

At times, COVID-19 infection rates vary within a single country and DCC requirements are adjusted. For example, in Germany, a Green Pass is mandatory—according to the “3G” rule (“geimpft (vaccinated), genesen (recovered) and getestet (tested)”) — whenever “states reach 35 Covid cases per 100,000 people within seven days”, the Local reported. And yet, in Brandenburg, the requirement for a DCC only applies when the infection rate reaches 20 cases per 100,000 within seven days. And, “in Baden-Württemberg, Berlin, Lower Saxony, Rhineland-Palatinate and Saarland, this policy applies regardless.”

Even more striking is the case of the United States. According to a recent tally by the MIT Technology Review, "7 states have active vaccine certification apps", while "22 states have banned the systems to some degree”.

Left to the authorities of member states, domestic European DCC schemes have not only been applied in different ways, but they have also been judged differently by national courts. In Spain, for example, regional high courts rejected—albeit only at first—the idea of a mandatory Green Pass to enter bars, restaurants, sports centers, and cultural venues. The consistent argument was that the measure would have a discriminatory effect, and, as previously reported by Jose Miguel Calatayud, “could violate people's rights without offering enough benefits for public health”.

However, in France, the country’s top constitutional authority—the Constitutional Court—approved Macron’s Green Pass plan arguing that it represents a "balanced trade-off" between public health concerns and personal freedom.

No end date is in sight for most DCC schemes. At the time of writing, Denmark is the only country to have announced an end to domestic COVID pass requirements, on 1 September, citing “record high vaccination rates”. “The pandemic is under control,” said health minister Magnus Heunicke. Meanwhile, countries like Scotland and Belgium are only just beginning to adopt a DCC pass for similar uses.

What is the purpose of a domestic COVID certificate?

Distilling a rational, informed assessment of the domestic use of DCCs is complex. The uses of DCCs vary so much from country to country, and region to region. And yet, an even more fundamental ambiguity risks plaguing any efforts of evaluating domestic DCCs in an evidence-based fashion: the fact that we’re not even sure why they are deployed.

What is the precise objective of adopting a DCC for domestic uses? The answer to this question is not simple. Are they a behavioral incentive to vaccination? A way to gradually introduce the population to the idea of a compulsory vaccination scheme—thus making them more acceptable? Are they being used to curb infection rates while safely reopening the economy or to shield individuals from infection altogether in certain social settings? And can we still think of domestic uses of DCC passes as an ‘incentive’, when they effectively shut someone who does not have a DCC out of most social activities?

Most governments proposed a mixed bag of all these intentions, while carefully avoiding dealing with the details and complexities of the topic. According to the literature, this is problematic in terms of privacy, security, and fairness.

The governments of France and Italy both claimed success after a sudden boost in vaccinations following the introduction of DCC schemes in both countries. Mainstream publications immediately supported the idea, writing about the “success” of Macron’s scheme (among them, Politico), and how the French President “eyes victory over Covid vaccine pass protesters” (Financial Times)—even in the face of widespread claims of fake certificates on the black market and seven consecutive weeks of street protests.

Causal powers were attributed to the pass by both Italian and French authorities in the complete absence of any rigorous study of the effects of its deployment. In an interview with the Italian newspaper La Repubblica, French health minister Olivier Véran argued that “vaccination rates spiked thanks to it”, even containing the “fourth wave” of the pandemic in the country. While, on the same day, the Italian Deputy Health Minister, Vincenzo Sileri, claimed that the domestic pass is a “very effective” screening method in an interview with Corriere della Sera—even though patchy enforcement had already been a matter of controversy in the country. Minister of Public Administration, Renato Brunetta, even argued that Italy’s GDP would reach 7% by the end of 2021 thanks to the domestic Green Pass.

Hasty assessments were common in other countries as well. For example, Scottish Health Secretary, Humza Yousaf, stated that the benefits of adopting a domestic COVID pass for nightclubs and large events outweigh the concerns—even though we have no rigorous way of comparing them.

One of the main arguments usually provided by government officials in response to such concerns—Yousaf included—is that a domestic DCC would prevent future lockdowns. However, AlgorithmWatch could not find any scientific evidence to support that claim.

History, unfortunately, won’t come to the rescue

Can history help us judge domestic vaccine passports? It’s a thorny issue.

On the one hand, “the use of health certificates – also referred to as ‘health passports’ or ‘vaccine passports’ – is not new”, wrote University of Sussex Professor John Drury and colleagues in ‘Behavioural responses to Covid-19 health certification: a rapid review’. “Printed health passes were used in Europe from the late fifteenth century to allow travel and trade while controlling the spread of plague”, certifying “only that the bearer had come from a city that was free from plague”. Vaccination certificates were also adopted for the mandatory smallpox vaccine in Venezia in the 1850s, and by the government of British India in the 1890s against the plague.

On the other hand, “If history is any indication”, argued CNN’s Scottie Andrew, “the adoption of vaccine passports won't happen smoothly or all at once. They were difficult to enforce in the 1890s — and if more Americans and international citizens resist, the same could be true in 2021 and beyond”.

This does not mean that vaccine passports are or have always been worthless. Actually, the opposite: “Throughout history, health certificates were used to document protection from contagious diseases, such as inoculation with cowpox against smallpox and yellow fever, and thus they are a well-proven public health tool to control epidemic diseases”, wrote Harvard professor Lin Chen and colleagues in ‘COVID-19 health passes: current status and prospects for a global approach.’

Furthermore, being paper-based and of a single, uniform type—decided by the World Health Organization (WHO)—those certificates were more easily measurable compared to contemporary digital apps, said Chen in a conversation with AlgorithmWatch. “For previous certificates there have been recommendations and requirements that are either agreed upon or clear, and have been for decades.” None of this is true of digital COVID certificates, especially for their domestic uses — for which WHO guidance was only published in August 2021, by which time most national schemes were already planned or underway.

Nonetheless, history could have warned us about the shortcomings of vaccine certification. Many of the issues that were encountered in previous schemes are still relevant today, in terms of enforcement and acceptance. When the government of British India tried to enact a pass scheme to certify that the holder was vaccinated against the plague, “colonized people living in India then saw government-mandated vaccine certificates as an invasive measure meant to curb travel and control citizens' movements”, wrote CNN—reminding us of both current worldwide street protests leading to claims of the allegedly “Orwellian” features of the COVID pass, and the much more credible concerns about the potentially discriminatory outcomes of domestic DCCs from civil society organizations.

There is, however, no precedent for the use of vaccine certificates as pervasive as the one we are witnessing with COVID-19 passes. “As far as a pandemic situation goes, there's really no historical example,” Chen concluded.

This leads back to the initial question: do they work?

“Passportizing immunity” is not necessarily a good idea

Let’s start at the original intent of DCC schemes—to allow freedom of movement. This is what the EU worked hard to achieve: “When travelling, the EU Digital COVID Certificate holder should in principle be exempted from free movement restrictions”, stated the EU Commission.

During the recent 2021 State of the Union address, EU President Ursula von der Leyen was quick to detail what this means in numbers, “more than 400 million certificates have been generated across Europe”, that “42 countries in 4 continents are plugged in” and, above all, this means that “when we act together, we are able to act fast”.

However, acting ‘fast’ implied room for member states to impose further restrictions, if national health authorities deemed them necessary to fight the pandemic. And they did, argued Laura Bialasiewicz, Professor of European Governance at the University of Amsterdam, and co-editor of a ‘Symposium on COVID-19 Certificates’ on the European Journal of Risk Regulation, in a conversation with AlgorithmWatch. “How do you measure whether the EU COVID certificates have been successful? Well, the stated measure is facilitating movement,” she said. “So, you should see if this has liberalized travel, and has reduced limitations”. According to Bialasiewicz, the answer to that question is, “only in part, because member states have adopted the certificate, but they are still imposing additional measures. That is already a partial failure.”

Also, and more importantly, the whole idea of the EU DCCs works around the assumption of “passportizing immunity”, Bialasiewicz said. This means presuming that your COVID passport states that you are immune if you have been vaccinated. Authorities are “presuming that the certificates are actually doing what they promised, which is creating safe travel,” she claimed; but now that we know that even vaccinated individuals can be carriers of COVID-19, a vaccine passport will not actually guarantee “safe” travel, said Bialasiewicz: “If the certificate is supposed to facilitate safe travel, well, it's not doing that.”

Interoperability issues have also plagued the system from the start. For example, individuals who received jabs with vaccines that were not recognized by European health authorities—in particular, from India and African countries—were excluded. This translated into unnecessary administrative and financial burdens for vaccinated individuals, so much so that, "the equitable treatment of persons having received their vaccines in countries profiting from the EU-supported COVAX Facility” would be “put at risk” as a result, wrote the African Union Commission and the Africa Centres for Disease Control and Prevention.

But—these issues aside—do vaccine passports have a positive impact on a person’s intention to travel at all? Not so much, argues a research letter (‘Exploratory analysis of the connections between acceptance of the Covid health passport and intention to travel: the case of Spain’). The letter “aims to explore the connections between pass acceptance, agreement with restrictions, attitudes and intention or willingness to travel” among 717 potential Spanish travelers.

In the letter, University of Cordoba researchers L. Javier Cabeza-Ramírez and Sandra M. Sánchez-Cañizares start from a noticeable—and rather surprising—premise: “to our knowledge, the effects of Covid health passport acceptance and the degree of agreement with restrictions on tourist arrivals as a security measure on people’s travel intentions have not yet been examined”. So, while, “attitudes and behavioural intentions are basic strategic metrics in the field of marketing and tourism”, they argue, “it seems that they have not been considered when assessing the effects of the implementation of the health passport.”

But they should have, as—according to the model they propose and the responses they obtained—“the implementation of the Covid passport could lead (…) indirectly, to lower travel intention among respondents, thus aligning with previous warnings”.

What this means is clear to the authors: “If the European authorities expect the introduction of the health passport to have a positive effect on the intention to travel, because of the security provided to travellers and residents by having an information document on Covid status, the results obtained do not seem to support this idea.”

Even so, COVID certificates are still more favorably perceived when seen as travel documents, rather than using them to gain access to venues and do certain activities. According to the aforementioned review of the literature on behavioral responses to COVID-19 certificates by Drury and colleagues, “public attitudes were generally favourable towards the use of immunity certificates (based on vaccination or on antibody tests) for international travel, protecting the vulnerable (e.g., in a care home setting), but generally unfavourable towards their use for access to work, educational or religious activities or settings.”

Studies indicate that, in terms of perception, it might be hard or even impossible to reach a consensus. For example, a (not yet peer-reviewed) survey among 1,315 respondents in the USA—after noting that “support was greater for using passports or certificates to enable returns to high-risk jobs or attendance at large recreational events than for returning to work generally”—concluded that “social consensus on the desirability of an immunity privileges programs may be difficult to achieve.”

Vaccine passports may backfire, studies suggest

The literature review by Drury and colleagues highlighted another troubling finding: that “the evidence reviewed on the potential impact of certification or mandates on vaccination rates suggests this would not increase vaccination rates and might even reduce them.”

Even worse, “disadvantaged groups are underrepresented in those getting tested and vaccinated and would therefore be disproportionately excluded in any Covid certification scheme”.

An increasing body of evidence, especially concerning the UK and Israel, seems to confirm their analysis. This puts a different perspective on the results boasted by France and Italy. If corroborated by further evidence in more countries and cultural contexts, this would seriously undermine one of the main rationales adopted to justify the introduction of domestic DCCs—namely, that their deployment boosts vaccination rates, gently (or rather not so) nudging the skeptical toward their jabs with the promise of having access to a free and safe social life again. The exact opposite might be happening instead.

At least for some. Culture, perceptions, and demographics should have been considered from the start, according to available literature, as the effect of incentive—the domestic DCC—may be very different across different communities and segments of the population, at least in certain countries. In fact, it is known that vaccine hesitancy “varies widely between countries”, wrote Julian Savulescu and colleagues at Oxford University in a Nature Medicine comment (‘Balancing incentives and disincentives for vaccination in a pandemic’), and “differs substantially between demographic subgroups”.

This is also consistent with one of the main prescriptions of the latest WHO guidance on the domestic uses of COVID certificates (labeled “health pass”): namely, that “the potential benefits, risks and costs of implementing” a domestic Green Pass or any equivalent solutions “should be assessed before introducing” them and their “associated structure”. Such an a priori impact assessment would have certainly provided researchers—and policy-makers—with much-needed information concerning the actual discriminatory effects in certain specific subgroups, and whether it is possible to avoid them, and how.

At the same time, to further minimize risks, the WHO stresses that it is also important to “monitor the effects” of the pass a posteriori, “in terms of positive and negative outcomes (e.g., impact on equity) and to consider potential interventions to mitigate negative outcomes”. Are governments considering this, and how?

Results from some recent studies in both the UK and Israel into the impact of the introduction of a domestic DCC on vaccination intentions strongly suggest that governments should be more careful in how they nudge the intentions of citizens when it comes to boosting vaccination rates. They should start following a more democratically designed process in their deployment decisions, as the WHO (belatedly) suggested.

Also, a better understanding of behavioral incentives, in general, seems to be required. As “some studies suggested that health certification might reduce Covid protective behaviours, including social distancing and handwashing”, the review concluded.

Imperial College researcher Talya Porat and colleagues, authors of a cross-sectional study on willingness to get vaccinated in Israel and the UK (‘“Vaccine Passports” May Backfire: Findings from a Cross-Sectional Study in the UK and Israel on Willingness to Get Vaccinated against COVID-19’), agree: “If we want to ensure enough people get vaccinated to control the spread of SARS-CoV-2, we need to understand the factors that affect people’s decisions,” their paper states. And the reason is straightforward: “If public health incentives like vaccine passports 'frustrate’ psychological needs – for example by making people feel a lack of free will over their decisions – then they might paradoxically reduce people’s willingness to get vaccinated.”

Porat and colleagues call this perceived loss of freedom of choice “autonomy frustration”, claiming that the results obtained from 1,358 participants in the two countries show that this frustration is negatively associated with willingness to vaccinate. Most of all, frustration is higher in Israel, where a domestic Green Pass has been adopted, than in the UK, where a pass has not been adopted.

An unprecedented survey of 17,611 adults in the UK by Alexandre de Figueiredo, a research fellow at the London School of Hygiene and Tropical Medicine, and colleagues (‘The potential impact of vaccine passports on inclination to accept COVID-19 vaccinations in the United Kingdom: Evidence from a large cross-sectional survey and modeling study’) reached similar conclusions: “Overall, we find that the introduction of passports for either domestic or international use has a net negative impact on vaccination inclination, once we control for baseline vaccination intent.”

The authors also analyzed the demographic subgroups who would be polarized toward vaccine hesitancy, as a result of the introduction of a COVID certificate: “younger age groups, Black and Black British ethnicities (compared to Whites), and non-English speakers are more likely to express a lower inclination to vaccinate if passports were introduced”, they wrote. Most notably, this is especially true “when these passports cover domestic activities as opposed to international travel”—which is still seen as less disagreeable by respondents.

According to de Figueiredo and colleagues, this finding can be summarized as “the vaccine passport paradox”, i.e., the finding that “the overall positivity of a population towards the introduction of passports may mask processes that alienate critical minorities and may possibly lead to an overall decrease in inclination to vaccinate.”

Also, since “there's been no proposed fixed end date to the passport,” claimed de Figueiredo in a conversation with AlgorithmWatch, “We'd be indefinitely discriminating, albeit indirectly, against Black communities, Asian communities, bilingual speakers. We’re effectively shutting them out of society.”

The authors point out that “even if it is accepted that our data reflect genuine intentions, these are still not the same as actual vaccination uptake”, and, therefore, “we cannot be definitive about the real-world impact of introducing such passports”. And yet, de Figueiredo argues that “the public health benefits of passports (…) appear vague and uncertain”.

But then again, what about the boost in the number of vaccinations in France and Italy? These gains might be real, but short-lived. “Even if government pressure causes people to get vaccinated now, they may be less willing to receive a booster dose or a vaccine against new variants in future”, Porat and colleagues argued in their paper.

During his conversation with AlgorithmWatch, de Figueiredo agreed that this might well be the case: “those people that have protested, are they now less likely to take a COVID vaccine? I would suggest that they are,” he said. Why? Because in France the incentive came at a relatively early stage of the vaccination campaign, the researcher claims, and some might simply have anticipated a choice that they would have made anyway—whereas, for others, this could result in an impression of coercion that can have lasting consequences.

“We may have achieved a short-term benefit in terms of vaccinating them now against COVID,” de Figueiredo argued, “but what is the damage that has been done to trust? Are they now less likely to trust the government when it comes to other things?”

A recent survey conducted in Israel (‘Incentivizing Vaccination Uptake The “Green Pass” Proposal in Israel’)confirmed that incentives “may not be sufficient to overcome health concerns or doubts regarding efficacy and safety of these novel vaccines”, wrote Rachel Wilf-Miron, Vicki Myers and Mor Saban—all the while confirming the importance of not damaging trust: “Creative use of incentives is likely to boost vaccination rates in some groups, whereas other groups will need more to allay their concerns, which should not be dismissed. To build trust, authorities need to understand these concerns and provide appropriate, transparent, and easily accessible information”.

This is hardly what we’ve witnessed over the last months.

Do domestic vaccine passports curb infections?

A second argument to justify the introduction of domestic DCCs, as we’ve seen, is that they help curb infection rates. But is this true?

A New Scientist investigation into the alleged effectiveness of such passes makes the ideal conditions—and why they can’t be met—perfectly clear:

“If vaccines provided complete protection against transmission, if tests for infection were completely accurate and if everyone stuck to the rules, COVID passes would be 100 per cent effective at, say, preventing people going to nightclubs infecting others there. But not everyone follows the rules, not all tests for infection are highly accurate and some vaccinated people can still get infected and infect others.”

This means that “COVID pass schemes will only lower the risk of infection rather than stop it”, the article concludes. But “by how much isn't clear. Surprisingly, there have been no real-world trials, nor even any modelling studies relevant to the current situation in wealthy countries, as far as New Scientist can establish.”

Crucially, however, studies around the efficacy of COVID-19 vaccines show that it might be problematic to rely on domestic DCC schemes altogether: “These studies together suggest that if the aim is to prevent outbreaks, many vaccines aren't effective enough for vaccine passports to work and even those that are don't remain so for long”, argues the New Scientist investigation.

Arguably, this can be seen in how the pandemic evolved in Israel, even as a seminal domestic Green Pass scheme was being enacted. The country was portrayed as a success story last spring because of high vaccination rates and the vaccine certificate scheme. Nonetheless, Israel suffered a dire resurgence of the virus over the summer of 2021. So bad was the resurgence that the pass, which had been discontinued, was reintroduced. “Israel now has the second-highest level of new cases per capita in the world and the coronavirus wards that were closed in April have all reopened”, wrote the Evening Standard at the end of August 2021, amid reinstated restrictions on gatherings and commercial and leisure activities. Isn’t this precisely what a domestic DCC scheme was supposed to avoid in the first place?

“Israel was the first to introduce a nationwide pass scheme, and some have said that that has been successful,” said University of Sussex social psychologist John Drury in a Zoom conversation with AlgorithmWatch. “But there's a [confounding factor], because at the same time they were running that scheme they were also running really effective community engagement programs. So, certainly the vaccination rate went up and they have been successful, but whether we can attribute it to the passport scheme, or to other things they were doing is not clear.”

Normalizing surveillance through a “performative device”

What is clear to many of the experts AlgorithmWatch spoke to is that domestic DCC schemes play into a well-established trend in technological responses to the pandemic: the normalization of health surveillance devices.

“What has happened with the pandemic,” said Marcel Salathé, a digital epidemiologist and associate professor at the École Polytechnique Fédérale de Lausanne, is that “people are very willing to take extra steps right in the name of the pandemic response that are actually not necessarily from an epidemiological perspective—and then they suddenly become normal, expected even.”

This comes with more unpleasant consequences, he said. First of all, “whenever you do something like this, that's rather strict and severe, you should always demonstrate that you have tried everything else, and I would say in most countries in Europe not everything else has been tried.”

Also, contrary to contact tracing apps, an individual cannot just choose not to use a DCC: COVID pass schemes are mandatory.

Finally, there are legitimate fears of state surveillance. “In principle, I don't know what's going on in the reader device” that checks an individual’s COVID status, argued Salathé. Could data be stored centrally by the government, so that the COVID pass digital infrastructure ends up “basically tracking what everybody is doing, when, and with whom?” he asked. With exposure notification apps—according to Salathé—thanks to their decentralized architecture, that was simply not feasible—but that’s not necessarily the case with DCCs. And where have digital contact tracing apps gone, one might ask? Weren’t they supposed to be crucial in the fight against the pandemic?

Governments all over the world seem to have forgotten about contact tracing apps, shifting their communicative strategies to COVID pass schemes—rather than integrating both. Too bad, says Harvard’s Lin Chen, as the integration of contact tracing data with COVID pass schemes, might have provided an avenue to better investigate the effectiveness of domestic DCCs—even though “I think people will object to that because of the privacy issues,” she added.

Conclusions. It is hard—but necessary—to have an evidence-based debate about COVID certificates

Something must be tried. However, according to the researchers AlgorithmWatch talked to, as things stand, it is hard to imagine a proper evidence-based debate about the domestic use of COVID passes.

“Certificates are hard to measure,” said Chen. “There are so many practices…”

But is it possible to find some kind of metrics? “It’s an extremely hard question. I think it would be extremely hard to measure something like this,” agreed de Figueiredo, who argued that he’s “yet to hear a good scientific argument put forward” in favor of such pass schemes.

Bialasewicz agreed: “How do you start an evidence-based discussion? It's really difficult,” she said. “Precisely because there was no specified endpoint,” to COVID pass schemes. What can and should be measured, however, is “the political effects that these passes are already having.” For example, popular protests in the streets in several countries. Protests, she noted, that are directed at individual national governments, rather than the EU, showing how absent the EU has been in shaping the domestic uses of DCCs.

In general, the way in which the debate around such tools has been shaped internationally by health authorities might end up discouraging rational, evidence-based inquiry into their effectiveness and actual properties. For example, researchers Stefania Milan, Michal Veale, Linnet Taylor, and Seda Gürses argued in a recent paper (‘Promises Made to Be Broken: Performance and Performativity in Digital Vaccine and Immunity Certification’) that domestic COVID passes have an intrinsic narrative and performative element to them: “The narratives and negotiations involved in establishing a certification regime involve a strong element of performance that is linked to national and international political orders”, they wrote.

According to this view, governments “publicly perform the rationale for its effectiveness and desirability, so as to achieve public buy-in and participation”, and it is this performance that “creates the impression of effectiveness on the part of government, while discouraging critique and resistance”.

This is not an accident, but part of the system argued the authors: “In the case of immunity certification specifically, incomplete and constantly developing scientific knowledge regarding the epidemiological processes involved in COVID-19 transmission meant that this technological performance also requires, and feeds on, the suspension of disbelief regarding existential uncertainty on the part of both the public and those devising the intervention.”

We might not be able to have an evidence-based discussion about the domestic uses of COVID passes—or even understand what that discussion should look like. The conclusion from Milan and colleagues hints that—under the false promise of total safety—we can however expect an abundance of narratives about the performance of COVID passes.

In other words, we might not get the evidence about the effectiveness of domestic COVID passes—but they’ll likely keep their “impression of effectiveness” nonetheless. Unfortunately, that might well end up being all that we’re left with.

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