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First study examining the impact of COVID-19 certification on vaccine uptake in six countries suggests it led to increased vaccination uptake, but this depended on prior levels of vaccine coverage and availability. Countries starting at lower-than-average COVID-19 vaccine coverage (France, Israel, Italy, Switzerland) experienced a large uptick in vaccination, but there was no significant effect in Germany where vaccine coverage was already high, or in Denmark where vaccine supply was limited. Uptake increase was greatest in under 30s. When restrictions applied only to nightclubs and large events, the largest increases were among under 20s. COVID-19 certification could help increase uptake in vaccine complacent groups – such as younger people, according to the study.

COVID-19 certification led to increased vaccination uptake 20 days before and 40 days after introduction, in countries with lower-than-average vaccination coverage, according to research, published today in The Lancet Public Health, led by Professor Melinda Mills, director of Oxford’s Leverhulme Centre of Demographic Science.

COVID-19 certification, or ‘vaccine passports’, require people to have proof of complete vaccination, negative test, or COVID-19 recovery certificate, to access public venues and events (e.g. restaurants, concerts, hairdressers). As well as helping to prevent the spread of COVID-19 in public venues, it has been suggested that certification might encourage more unvaccinated people to get vaccinated. But, some survey-based evidence has suggested participants report they would be less likely to get vaccinated if certification were introduced.

It has been suggested that certification might encourage more unvaccinated people to get vaccinated. But, some survey-based evidence has suggested participants report they would be less likely to get vaccinated if certification were introduced

The study linked COVID-19 certification, introduced from April to September 2021, to vaccination uptake in six countries where certification was legally mandated (Denmark, Israel, Italy, France, Germany, Switzerland). Modelling was used to estimate what vaccine uptake would have been without certification in the countries, based on vaccination uptake in similar control countries without certification.

According to the study, in countries where vaccine coverage was previously low, certification was associated with a significant increase in additional vaccine doses per million people - ranging from 127,823 in France, to 243,151 in Israel, 64,952 in Switzerland and 66,382 in Italy. However, in Denmark and Germany, where there were higher average vaccination rates before certification was introduced, the study shows no significant increase in vaccination.

We observed a significant uptick in anticipation of restrictions...around 20 days before introduction, which lasted up to 40 days after, but the context of existing vaccination uptake, vaccine hesitancy, levels of trust in authorities, and pandemic trajectory was crucial

Professor Melinda Mills

Lead author of the study, Professor Mills says, 'As mass vaccination programmes continue to play a central role in protecting public health in this pandemic, increasing vaccine uptake is crucial both to protect the individuals immunised and break chains of infection in the community. Our study is an important first empirical assessment of whether COVID-19 certification can form part of this strategy. Overall, we observed a significant uptick in anticipation of restrictions coming into place around 20 days before introduction, which lasted up to 40 days after, but the context of existing vaccination uptake, vaccine hesitancy, levels of trust in authorities, and pandemic trajectory was crucial to the impact.'

Compared to the control countries, daily COVID-19 case numbers decreased after implementation in France, Germany, Italy, Switzerland, but increased in Israel and Denmark. Many countries implemented certification as a response to rising cases, making it difficult to assess the effect of certification on reported infections. The authors say this highlights the importance of taking account of the phase of infection trajectory, historical and contextual circumstances when the intervention is introduced.

Co-author, Oxford Nuffield College research fellow, Dr Tobias Rüttenauer, adds, ‘We know that certain groups have lower vaccine uptake than others and it may be that COVID-19 certification is a useful way to encourage vaccine complacent groups, such as young people and men, to get vaccinated. However, certification alone is not a silver bullet for improving vaccine uptake and must be used alongside other policies. Vaccine hesitancy due to lack of trust in authorities, which is common among some minority ethnic and lower socioeconomic groups, may be addressed more successfully through other interventions, such as targeted vaccine drives and community dialogue to generate more understanding about COVID-19 vaccines.’

It may be that COVID-19 certification is a useful way to encourage vaccine complacent groups, such as young people and men, to get vaccinated. However, certification alone is not a silver bullet for improving vaccine uptake 

Dr Tobias Rüttenauer,

Finally, the authors point to several issues associated with certificates that policymakers should consider. This includes the risk of exacerbating inequalities among communities that have lower uptake, generating inequality in access to public spaces where COVID-19 vaccine roll-out is staggered by age and vaccine eligibility differences, entrenching digital divides if passes are electronic, and data privacy concerns.

This study received funding from The Leverhulme Trust and European Research Council. It was conducted by researchers at the Leverhulme Centre for Demographic Science, Nuffield College and Pandemic Sciences Centre, University of Oxford. Click here to read the full article.