The relationship between COVID-19 certification and vaccine uptake

Many countries have either introduced or are contemplating introducing compulsory coronavirus disease 19 (COVID-19) certification. These certificates could be obtained using proof of complete vaccination, negative PCR test, etc. The certificates are aimed at helping return, gradually, to common day-to-day activities like accessing hospitals, gyms, large social events, indoor hospitality, etc.

Study: The impact of mandatory COVID-19 certificates on vaccine uptake: Synthetic Control Modelling of Six Countries. Image Credit: Robert Avgustin/ Shutterstock

But, what is the effect of vaccine certificates on vaccine uptakes? There is a lack of empirical research on this topic, and most of the evidence we have is anecdotal. A new study has been published on the medRxiv* preprint server that seeks to fill this research gap by analyzing the impact that the introduction of COVID-19 certificates has had on vaccine uptake.

A new study

Some recent review studies have concluded that the quality and quantity of existing studies are low. There is no evidence that certification has brought about an increase in vaccine uptake. Analyzing this relationship is important because vaccine uptake remains low in some sub-groups of individuals (youth, men, and some ethnic minorities). It would be useful to understand if certification can overcome at least some of the vaccine hesitancy. Moreover, vaccination helps not only the immunized but also the community by reducing the risk of transmissions.

The data for this study was collected from a few different sources. Our World Data provided information on COVID-19 related health indicators, Oxford COVID-19 Government Response Tracker (OxCGRT) provided country-level information on non-pharmaceutical interventions, and the European Centre for Disease Prevention and Control (ECDC) provided information on age-related issues. The last data point was the 28^th of September 2021.

Six countries were selected based on data availability and the fact that they implemented COVID-19 certification between May and August 2021. These countries were Denmark, France, Germany, Israel, Italy, and Switzerland. These six countries were compared against a list of twenty other countries that served as the control group.

Main findings

The main outcome variable used for the analysis was the daily COVID-19 vaccine doses administered per capital, using a seven-day smoothed moving average. The key finding was that the COVID-19 certification led to a quick rise in vaccination rates. The effect was quite significant before implementation and persisted after implementation as well. The results, however, varied depending on the pre-implementation vaccine uptake levels and the reasons for implementation.

Countries such as France, Italy, and Israel with lower pre-intervention uptake rates, showed more pronounced effects. In the case of Germany, which had high uptake rates, no significant effect was observed. The same was in the case of Denmark, where the intervention was implemented at a time of low vaccine supply. Scientists opine that it is not easy to gauge the impact of certification on COVID-19 infections, but overall, vaccine certificates should decrease infection rates by encouraging people to get vaccinated.

Researchers conducted a detailed age-specific analysis and observed that the highest uptake was noted for those below twenty years of age, followed by those in the 20-29 age range. Targeted interventions had some interesting effects as well. When a certificate was required to access particular events (nightclubs, events >1,000 people), Switzerland's youngest group showed the highest uptake.

When the certification was extended to other settings, e.g., hospitality and leisure, an increase was observed in older age groups. Scientists mentioned that these findings should be interpreted concerning the levels of vaccine uptake, vaccine hesitancy, people's trust in the government and its programs, and the overall pandemic trajectory. They also highlighted that certification, by itself, is not a silver bullet to raise vaccine uptake. Certification should be combined with other measures, such as geographically targeted interventions.

Conclusion

This study provides the first empirical assessment of the relationship between COVID-19 certification and vaccine uptake and shows that certification could increase vaccine uptake. Scientists highlight that while interpreting the results, one should also consider additional factors like age eligibility changes and pandemic trajectories. However, it has certain limitations that include the inability to isolate the effect of confounders (socioeconomic status and ethnicity) and lack of access to granular data on age-based uptake for all countries.

It must also be noted that the vaccine certificates were introduced in different countries for different reasons. France, Italy, and Israel incentivized vaccine uptake using certification for entry into desirable events or settings. Belgium, on the other hand, wanted to avoid the reinstatement of restrictions. If the current study results were to be transferred to other settings, these contextual aspects should be carefully considered.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Dr. Priyom Bose

Priyom holds a Ph.D. in Plant Biology and Biotechnology from the University of Madras, India. She is an active researcher and an experienced science writer. Priyom has also co-authored several original research articles that have been published in reputed peer-reviewed journals. She is also an avid reader and an amateur photographer.