Kutatás vezetője: Dr. Karsai János
Intézmény: University of Szeged
Leírás: A Varicella vírus gyerekkorban bárányhimlőt okoz, majd a szervezetben maradva, felnőttkorban kiújulva övsömör alakulhat ki. A hatás a teljes társadalmat érinti és egész életen át tart. A bonyolult hatásmechanizmus is különösen fontossá teszi modellvizsgálatokat és a megfelelő védőoltási stratégiák kialakítását. Korábbi kutatásainkban a hazai adatok felhasználásával egyszerű modellt készítettünk, kvalitatív vizsgálatokat végeztünk, és megvizsgáltuk a rendszer paramétereinek valamint az adatgyűjtés pontosságának hatását is. A projektben hibrid korstrukturált modellt építünk, és a különböző védőoltási stratégiák hatását vizsgáljuk. Foglalkozunk az indirekt hatások következményeivel is. Matematikai újdonság a reprodukciós számok segítségével a küszöbdinamika kiterjesztése a modellekre.
Varicella
Varicella causes not only the chickenpox, but also the herpes zoster. Almost every individual infected by varicella becomes susceptible to herpes zoster later in life due to reactivation of the latent virus. Immunity is waning in time, but boosting by re-exposure may prolong this immune period. Increased vaccination thus reduces this exogenous boosting effect, and may provide other indirect consequences as well, such as delaying the age at infection through reduced exposure to the virus. While chickenpox is typically a childhood disease, zoster effects elder age groups, thus an age structured model incorporating a realistic contact pattern is necessary. All these factors make varicella vaccination modelling more challenging.
The problem
Varicella is one of the most common infectious diseases of children, caused by the initial infection with varicella zoster virus (VZV), which can be effectively prevented by vaccine. It is the cause of chickenpox in children, but it is more dangerous if contracted at an older age. In Hungary, the vaccine is marketed for more than 15 years, but not part of the mandatory vaccination schedule, and vaccine uptake is relatively low. Varicella has high incidence and affects a large number of children: the average number of reported varicella cases is more than 40 000 per year, according to the KSH (Central Statistical Bureau) reports. Incorporation of varicella vaccination into the mandatory vaccination schedule is currently being under introduction in Hungary, planned from September, 2019. However no modelling studies have been done to carefully assess its impact on the future disease dynamics as well as the costs vs benefits.
Preliminaries
In our former project, based on the specialties of varicella infections, we built models with and without age-structure. We investigated the qualitative properties of the simple models, and fitted the parameters to the available annual and monthly reports available in Hungary. We incorporated different vaccination strategies into the models without age structure and detected the phenomena agreeing the observations in the real situations. Finally, we developed programming framework for further studies.
