1. Department of Pediatrics, Pavlov First Saint Petersburg State Medical University, 197022 St. Petersburg, Russia
2. Department of Infectious Diseases, Pavlov First Saint Petersburg State Medical University, 197022 St. Petersburg, Russia
3. Smorodintsev Research Institute of Influenza, 197376 St. Petersburg, Russia
4. Infectious Diseases Department No. 7, N.F. Filatov Children’s City Clinical Hospital No. 5, 192289 St. Petersburg, Russia