流行性感冒（Influenza）Photo by Andrea Piacquadi,See www.pexels.com.

Influenza (the flu) is an acute respiratory infection caused by influenza viruses. The influenza virus is mainly classified into types A, B, and C, with types A and B being the primary pathogens responsible for seasonal outbreaks. After infection, patients typically experience fever, cough, sore throat, muscle aches, and marked fatigue. For children, older adults, and individuals with weakened immune systems or chronic diseases, influenza can lead to severe complications such as pneumonia, myocarditis, and encephalitis, and may even be life-threatening.

According to data from the World Health Organization (WHO), influenza causes hundreds of thousands of deaths globally each year. The continuous mutation of the influenza virus and its ability to spread across regions necessitate annual adjustments in the vaccine composition based on the most recent circulating strains, resulting in variable vaccine effectiveness.

The effectiveness of the influenza vaccine is typically between 40% and 60%, and its performance is influenced by several factors:

1. Virus strain matching: The viral strains used in the vaccine must closely match the circulating strains of the current season; otherwise, the level of protection will be significantly reduced.
2. Population characteristics: The immune response to the vaccine varies among different age groups and health statuses. Older adults and individuals with underlying health conditions may have a weaker immune response, which can diminish the vaccine’s protective effect.
3. Type of vaccine: Common influenza vaccines include inactivated vaccines, live attenuated vaccines, and recombinant vaccines. Each type has its own strengths and weaknesses regarding immunogenicity and side effects, and clinical decisions are made based on the characteristics of the target population.
4. Severity of the flu season: In seasons where the virus spreads more widely and the circulating strains are more virulent, the vaccine may provide more significant protection. Even if it does not completely prevent infection, it can effectively alleviate symptoms and reduce the risk of complications.

Although the protective efficacy of the influenza vaccine may vary from year to year, annual vaccination has been proven to be one of the most effective measures for preventing influenza and its complications. Vaccination not only reduces the risk of individual infection and severe illness but also, through herd immunity, helps to decrease the transmission of the virus in the community, thereby protecting those with lower immunity or who cannot be vaccinated.

In addition to vaccination, several other measures can effectively help prevent influenza infection:

• Enhance personal hygiene: Regularly washing your hands with soap and water—especially after coughing, sneezing, or coming into contact with public areas—can significantly reduce the risk of virus transmission.
• Maintain proper respiratory etiquette: Cover your mouth and nose with a tissue or your elbow when coughing or sneezing, and dispose of used tissues promptly to reduce the spread of virus-laden droplets.
• Avoid crowded places: During peak flu seasons, try to avoid crowded or poorly ventilated locations to lower the likelihood of infection.
• Maintain a healthy lifestyle: Adequate sleep, a balanced diet, and regular exercise can help boost your immune system, enabling your body to better fend off viral infections.

For those already infected with influenza, in addition to symptomatic treatment, early use of antiviral medications (such as oseltamivir or zanamivir) can reduce the severity of the illness, shorten the recovery period, and decrease the risk of complications when administered at the onset of symptoms. Moreover, getting ample rest and ensuring adequate fluid intake are critical supportive care measures during recovery.

In summary, tackling influenza—a seasonal disease—requires a comprehensive approach to prevention. Regular vaccination, good personal hygiene, and timely treatment can significantly reduce the health risks associated with the illness, thereby safeguarding your health and that of those around you.

Reference: CDC - Flu Prevention