Modeling of vaccination and contact tracing as tools to control the Covid-19 outbreak in Spain

    According to a computational model by the Universitat de Lleida, the IREC and the Hospital Clínico de Barcelona, the protection measures would reduce Covid-19 infections by 19% more than vaccination alone.


    Researchers from the Universitat de Lleida (UdL), in collaboration with scientists of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM) and the Hospital Clínico de Barcelona, have developed a computational model to decipher the effects of vaccination and protection social measures against Covid-19, taking Spain as a case study.

    Starting from the basis that it is vital to identify strategies that allow the resumption of economic and social activities, protecting life and health systems, the scientists have used computational P System models, which carry out calculations using biologically-inspired processes. These models, which until now had not been used in human epidemiology, have served in this case to assess the effects of vaccination and the tracing of contacts with positive Covid-19 at the population level under different epidemiological scenarios and protection measures (social distancing, mask wearing and hand hygiene).

    Screenings on the Cappont campus (Photo: Universitat de Lleida).

    The results of the model, which have been published in the international journal Vaccines, show that reinforcing vaccination with protective measures would reduce infections by an additional 19%. On the other hand, they suggest that without the application of these measures, in a simulation period of 80 days, 56% of the Spanish population would contract the disease with a mortality of 0.4%. Assuming that 20% of the population were protected by vaccination in late summer 2021, the model estimates that at least 45% would have contracted the disease with a mortality rate of 0.3%. Both percentages would decrease significantly after the adoption of social measures, especially in combination with the tracing of at least 40% of the contacts.

    The model also shows that if 40% of the population can be vaccinated, even without protection social measures, the percentage of people who contract the disease would go from 56% to 34% and that of fatalities from 0.41% to 0.16%, compared to an unvaccinated population. With additional measures, the figures would fall to 14.5% of infected, 19% less, and mortality would be reduced to 0.10%.

    The scientific publication of this research is available at:

    The new computational model developed for the SARS-CoV-2 pandemic using the available epidemiological information is available at: