Influenza and Influenza-Like Virus Infection in Children Under 14 Years of Age: An Investigation of 725 Cases in the 2021/2022 Influenza Epidemic Season in Poland

BACKGROUND: Influenza in children poses a significant health problem worldwide. In this study we investigated 725 cases of influenza and influenza-like virus infection in children under 14 years of age in the 2021/2022 influenza epidemic season in Poland. MATERIAL/METHODS: The material for the study (nose and throat swabs) was collected during the 2021/2022 epidemic season. We analyzed 725 samples from the National Influenza Center, Department of Influenza Research at the National Institute of Public Health NIH-NRI or at 16 Voivodship Sanitary Epidemiological Stations across Poland. Quantitative polymerase chain reaction (qRT-PCR) was applied to determine the influenza virus type and subtype (in RNA isolated from positive samples). RESULTS: This study shows the high incidence of influenza among children under the age of 14. Most confirmed infections were caused by influenza A. The genetic material of the A/H1N1/pdm09 subtype was not found among the analyzed samples. The highest number of influenza A infections was among the youngest children (the 0–4 years age group). The most common influenza-like virus was respiratory syncytial virus (RSV). The greatest number of cases caused by this respiratory virus was registered among the youngest children (0–4 years). CONCLUSIONS: This study, which shows the high incidence of influenza among children under the age of 14, highlights the importance of regular influenza vaccination. Since children often play a dominant role in spreading influenza virus in the community, regular vaccination can have both health and economic benefits for all age groups.