Influenza

How is the flu spread?²

The flu is spread when droplets of an infected person enter an uninfected person's eyes, nose, or mouth. Additionally, flu may be transmitted through objects or surfaces (fomites). If an uninfected person were to come into contact with these fomites and then touch their eyes, nose, or mouth, they may become infected.

Symptoms^2,3

Symptoms of the flu can range in variety and severity. It is important to note that individuals who are infected may be able to pass on the disease before they show symptoms. Symptoms appear between 1 and 4 days after infection. Most symptoms clear up within 5-7 days; however, some symptoms may last for weeks.

Complications^2,4

In some cases, the flu may worsen and lead to complications. These complications can be especially dangerous for very young children/infants, immunocompromised individuals, and the elderly.

Flu Vaccines

Flu vaccines can prevent you from getting sick, especially during peak flu seasons.

How are flu vaccines made?^5,6

The flu changes each year, so production and development of flu vaccines varies year to year. Each year, in collaboration with the World Health Organization (WHO), the CDC predict the worst flu strains for the upcoming flu season. These recommendations are passed along to production sites to begin producing vaccines. All vaccines are tested for safety and effectiveness before distribution. More information on the three methods of flu vaccine production can be found here.

Flu Vaccine Effectiveness⁷

The flu is dynamic and varies year to year. Effectiveness, or the amount of disease prevented by the vaccine, ranges from 10% to 60%. The flu vaccine consistently confers some protection each year. For a deeper look into the flu vaccine's effectiveness over time, see here.

When should I receive my flu vaccines?⁸

Individuals older than 6 months can and should receive a flu vaccine each year as soon as they are available (~October of each year).

Individuals aged 6 months to 8 years old who have never received a flu shot should receive 2 doses, spaced 4 weeks apart. Otherwise, only 1 dose of any available type of flu vaccine is necessary each year.

How do I know if I'm vaccinated against the flu?

Vaccination records are your best bet in knowing your vaccination status.

Flu Vaccine Safety⁹

Safety profiles for flu vaccine are robust and the large majority of side effects are mild and temporary. Inactivated, (or killed) flu vaccines may be associated with Guillain–Barré Syndrome (GBS), depending on certain vaccine combinations and other underlying conditions. Estimates of GBS are roughly 1-2/1,000,000 persons. It should be noted that an individual's risk of GBS after influenza may be higher compared to after receiving a vaccination.

If you have any questions or concerns regarding safety, your physician will have the most up to date information and can help you make the best decision.

Flu Vaccine Side Effects¹⁰

Due to the wide variety and variance in flu vaccines, side effects, while mostly mild, may vary.

Inactivated Influenza Vaccine Side Effects

These are killed vaccines. Common side effects include:

Cell Culture-based Inactivated Vaccines Side Effects

These are killed vaccines that are egg-free.

Recombinant Vaccines Side Effects

Live, Attenuated Influenza Vaccine Side Effects

The Bottom Line

The flu can be dangerous, especially for young children and older adults. Vaccinations can prevent you or your family from catching the flu while also protecting those around you.