Every year, whenever the peak influenza season comes, there will be a number of influenza cases. Therefore, besides of children has a need to receive vaccination, it is recommended that teenagers and adults are also need to receive seasonal influenza vaccination to reduce the admission rates and death cases due to influenza-associated complications. In addition, the apparent symptoms of COVID-19 and influenza are similar. Both illnesses cause respiratory tract diseases, including fever, runny nose and sore throat, so it is difficult to distinguish between COVID-19 and influenza according to merely the clinical symptoms. As a result, even though children go out less often during the COVID-19 epidemic, parents should still stay alert.

Vaccination is one of the most effective ways to prevent seasonal influenza and associated complications, so people aged 6 months or above should receive seasonal influenza vaccination. For children under 9 years of age who have never received such vaccination before are recommended to receive 2 doses of seasonal influenza vaccination in the 2020-21 season.

New influenza strains appear from time to time and at irregular intervals. As the vaccine composition is updated every year in accordance with the circulating strains, it is suggested that people should receive seasonal influenza vaccination annually. After vaccination, it takes around two weeks for the body to develop antibodies to prevent the disease. Therefore, seasonal influenza vaccine should be given at least two weeks before the beginning of influenza season for proper protection during the influenza season.

The quadrivalent influenza vaccines (Northern Hemisphere winter disease) recommended by the World Health Organization (WHO) for the 2021-22 season contain the following:

• A/Victoria/2570/2019 (H1N1) pdm09-like virus
• A/Cambodia/e0826360/2020 (H3N2)-like virus
• B/Washington/02/2019 (B/Victoria lineage)-like virus
• B/Phuket/3073/2013 (B/Yamagata lineage)-like virus