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Even before covid passports were introduced, an international team of scientists from several European universities and institutes (including Wrocław, Warsaw, Trento, Vienna, Maribor, Malta and Crete) had decided to see how they might affect the coronavirus outbreak. In mid-May a publication that summarises the outcome of this analysis was released.

"The introduction of these passports," the researchers write, "is widely seen as a way to open up the economy and return to normal life, despite the ongoing epidemic." Unfortunately, a new mathematical model shows that the epidemic cannot be extinguished if passport holders are given only minimal or no restrictions.

This is for two reasons. Firstly, no vaccine prevents infection 100% of the time, so a fraction of those vaccinated are susceptible to infection and could potentially spread the virus. Finally, immunity does not last forever, it declines over time, and although we currently do not know how long the vaccine will protect us, an additional dose will probably be necessary.

In addition, new, more infectious variants of coronavirus may emerge to break down immune protection (although this latter possibility is not included in the model).

All this means that passport holders, freed from most restrictions and enjoying greater freedom, could become one of the vectors of transmission of the virus in Europe.

The mathematical model confirms this. In doing so, the researchers took into account many parameters: the effectiveness of current vaccines, the rate of vaccination, the estimated infectivity of the virus and the duration of immune protection. They also took into account the proportion of people who do not get vaccinated, as well as the level of restrictions for passport holders and the rest of the population.

Within a very wide range of these parameters, the epidemic first gradually dies out (as a result of an increasing proportion of vaccinated people), but... does not disappear, after a certain time it resurges. The number of infections starts to increase exponentially again, despite the fact that considerable restrictions are maintained for the unvaccinated.

It is passport holders, who, often unwittingly, will spread the virus, who will play an important role in this next wave of infections.

"At the current vaccination rate, some restrictions should also be maintained for passport holders to avoid further waves, " says co-author of the analysis Ph.D. Ewa Szczurek, a researcher at the University of Warsaw.

"In the real time horizon (up to two years), those in power have a lot of options," believes Ewa Szczurek. "They can start with giving passport holders a lot of freedom, while maintaining restrictions for others. However, in order to avoid further waves, they will have to impose more restrictions on the vaccinated over time, although the closer these restrictions are to those imposed on the rest of the population, the more it goes against the idea of the passport, which is supposed to guarantee greater freedom." Therefore, researchers believe that in the long term, passports will have to be abandoned and the same restrictions imposed on everyone.

The mathematical model suggests that the minimum level of these restrictions on social contact under favourable conditions should not be less than around 30%. In other words, the restrictions should be such that they reduce the number of social contacts by a third compared with the pre-pandemic situation.

"However, if we vaccinated sooner and if there were fewer people who do not want or cannot get vaccinated, the situation would look better," explains Ewa Szczurek. Another solution is to introduce passports only for a short period of time and to test those who are vaccinated. The idea is to avoid a situation where a passport is issued to someone who is not really immune to the infection.

"Covid passport holders should be tested extensively and regularly for antibody levels to detect vaccinated individuals who have lost or never gained immunity. Finally, temporary passports whose renewal depends on high antibody levels or recent (re-)vaccination could be considered," the researchers write.

"We are working on extending this work by looking at the delta variant, which will undoubtedly be dominant across Europe in a short while and will bring a fourth wave of infections," adds Ewa Szczurek.

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And once the pandemic is over, how do we assess the impact and the damage? How do we develop an action plan? The Periscope project brings together the best scientists and experts from 32 European universities, research institutes and think tanks. Gazeta Wyborcza is the only medium cooperating with them. The Periscope project is funded by the European Commission under the Horizon2020 programme.

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Translated by Chris Borowski

This is a translation of the article from July 1, 2021.

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