Incidence of acute respiratory infections in preschool children in an outpatient setting before and during Covid-19 pandemic in Lombardy Region, Italy oleh Chiara Mameli, Marina Picca, Roberto Buzzetti, Maria Elisabetta Pace, Raffaele Badolato, Claudio Cravidi, Gian Vincenzo Zuccotti, Paola Marchisio, for the Italian Society of Paediatrics Lombardy Section