Flu Shot: When Is Flu Season?

The CDC recommends getting a flu shot at the start of each year's influenza season. Flu season starts around September and ends in April in the U.S. It varies all over the world based on the climate. It typically starts in the fall and ends in the spring.

The flu shot can be administered via injection or a nasal spray. It contains dead or inactive influenza viruses that cannot cause an infection. The vaccine leads to the vaccinated person’s immune system creating antibodies that fight off the virus. That is how all vaccines work.

You might be wondering why you must get a new flu shot every year, while you only have to get vaccines for other diseases once. The viruses that cause the flu mutate rapidly, so new strains constantly emerge. This limits the vaccine's effectiveness because it only protects against the strains that it was developed for. As a result, the vaccine may only provide about 40% to 60% protection against the virus.

However, the protection that a flu shot provides extends beyond preventing the infection. It also prepares the vaccinated person’s immune system to fight off the virus, so they are less likely to develop complications or need significant medical treatments if they get infected. Children below the age of five, people over 50, and pregnant people have a higher risk of developing complications due to the flu.

Understanding the flu season

The influenza virus can be spread throughout the year, but the risk of getting it peaks during the fall and winter months, typically in December and February. The vaccines made to combat the virus each season are developed to protect against the strains of the viruses that are expected to have the most significant impact. Flu vaccines used in the U.S. typically protect against four strains of the flu virus.

Other respiratory infections share similar seasons with the flu, and some even share similar symptoms. For example, the rhinovirus (a.k.a. the common cold) has a similar peak season. It also shares symptoms with influenza, like a runny nose, sneezing, and a sore throat. Flu vaccines are available throughout the year, and each year’s vaccine is developed to protect against the specific strains of the viruses that are spreading the most.

Benefits

According to the CDC, the benefits of getting a flu vaccine every season include:

• The flu vaccine reduces a person’s risk of becoming infected with the influenza virus by up to 60 percent
• People who have been vaccinated often report less severe symptoms than those who have not been vaccinated
• The vaccine reduces the need for hospitalization by up to 80% in adults and 74% in children
• The vaccine significantly reduces the risk of an influenza infection becoming life-threatening
• The vaccine reduces the risk of people with chronic health issues, like heart disease, developing complications due to the flu