Influenza virus: Underestimated enemy respiratory infections and deaths are directly affected. Influenza is an acute respiratory infectious disease caused by the influenza virus, and it is also one of the huge health threats that humans face every year. Influenza spreads rapidly and can cause seasonal epidemics every year, mainly caused by influenza A and B viruses. On a global scale, seasonal influenza epidemics can cause 3-5 million severe cases and 29000-650000 respiratory disease related deaths every year. Influenza viruses directly invade the respiratory system of the human body and can cause various life-threatening serious complications such as viral pneumonia, secondary bacterial pneumonia, and acute respiratory distress syndrome. According to a research analysis, influenza infection increases the susceptibility to pneumonia by about 100 times within a week. Among children aged 0-14, compared to those who have not contracted the flu, symptomatic flu infected children have a significantly increased risk of developing pneumonia within 30 days of onset, especially within one week after infection, with a 8.3 fold higher risk of developing pneumonia. The burden beyond the respiratory tract should not be underestimated. In some cases, influenza infection may also cause various non respiratory complications - affecting the heart, central nervous system, and other organs or systems. Research has found that for people aged 40 and above, the risk of myocardial infarction and stroke increases by about 10 and 8 times, respectively, within 3 days after influenza virus infection. In a retrospective cohort analysis, patients with type 2 diabetes had a 74% increased risk of abnormal blood glucose events during influenza infection. In addition, more than one fifth of elderly people aged 65 and above suffer from the loss of independence caused by influenza. Influenza puts enormous pressure on the healthcare system and society. It is estimated that on average, more than 25000 people worldwide are hospitalized with influenza every day. A retrospective analysis showed that the hospitalization rate and cost of influenza patients with complications were 1.5 times and 2 times higher than those without complications. According to a systematic review and meta-analysis in China, children under the age of 5 have the highest hospitalization rates and outpatient visits for influenza like diseases due to influenza. People over 65 years old and under 5 years old are the main sources of influenza incidence and death burden, with the average economic burden of the elderly being the heaviest. Influenza vaccine: Prevention is not limited to influenza vaccination, which is a very effective and cost-effective method for preventing influenza and related complications. It is generally recommended that high-risk groups such as pregnant women, children aged 6 months to 5 years, the elderly, and those with underlying diseases, healthcare workers, and caregivers receive influenza vaccines once a year. The results of a multicenter prospective intervention study in China show that vaccination with influenza vaccine and pneumococcal polysaccharide vaccine, whether administered alone or in combination, can significantly reduce the risk of acute exacerbation of chronic obstructive pulmonary disease and pneumonia in patients, and reduce related hospitalization rates. At the same time, it can also significantly reduce medical costs. In addition to reducing the risk of influenza infection, early vaccination against influenza in patients with myocardial infarction or high-risk coronary heart disease can reduce the combined risk of all cause death, myocardial infarction, or stent thrombosis, and reduce the risk of all cause death and cardiovascular death at 12 months. Therefore, receiving influenza vaccine may be considered as part of hospitalization after myocardial infarction.