[Analysis of vaccination strategy against COVID-19 in Spain. The scientific basics (may 2022).]

After about a year and a half (at the moment these lines are being written) since the start of the massive vaccination campaign in which, thanks to the high coverage achieved in all groups eligible for vaccination, it has been possible to significantly reduce the morbidity and mortality due to COVID-19, it is important to review the scientific basics that have supported the recommendations implemented to date and those that could be adopted in the near future taking into consideration the epidemiological situation. The objective of this article is, therefore, to address the foundations of some of the technical decisions proposed by the Committee on Programme and Registry of Vaccinations (National Immunization Technical Advisory Group in Spain) and the Technical Working Group on Vaccination against COVID-19. Throughout the eleven updates of the Vaccination Strategy against COVID-19 in Spain, several issues pose intense debate as the vaccination intervals between doses, the convenience of using different types of vaccines, the use of heterologous schemes of vaccination, the benefits of hybrid immunity and the use of a fourth dose (second booster dose) for selected populations. All this without forgetting essential aspects of safety of vaccines. This article is divided into the following sections: Vaccination intervals;Heterologous or mixed scheme;Hybrid immunity (vaccination after infection and infection after vaccination [breakthrough]);Second booster dose.

Predictions of three mathematical models related with the COVID-19 Vaccination Strategy in Spain. June 2021

The Ministry of Health has coordinated three studies that have estimated the impact of the COVID-19 Vaccination Strategy in Spain. The models aim to help how to establish priority population groups for vaccination, in an initial context of dose limitation. With the same epidemiological and vaccine information, the results of this three different mathematical models point in the same direction: combined with physical distancing, staggered vaccination, starting with the high risk groups, would prevent 60% of infections, 42% of hospitalizations and 60% of mortality in the population. These models, which can be adapted to the new available scientific evidence, are dynamic and powerful tools for the evaluation and adjustment of immunization programs, promoting research on this field, and helping to achieve more efficient results in health.

Impact of vaccination against COVID-19 in children aged 5-11 years: a mathematical model

On November 25, 2021, the European Medicines Agency (EMA) authorized the presentation of Comirnaty vaccine (Pfizer- Biontech) for children between 5 and 11 years of age. In our country, this vaccination began on December 15, after it was approved by the Public Health Commission. A mathematical model has been developed to evaluate the possible impact of this vaccination and contribute to assessing the risk-benefit balance. The model parameters were adjusted including all those characteristics that may influence the impact of childhood vaccination. The results indicate this vaccination involves a significant reduction in the number of infections, and to a lesser extent in the number of hospitalizations and deaths. This reduction will be more important in a future epidemic wave, when this population has been fully vaccinated. Mathematical models can be very powerful tools to predict the impact of vaccination in different epidemiological situations, and help to adjust vaccination programs to be more efficient.