Myths and Truths about Seasonal Influenza and the Flu Vaccine

Influenza patient

Washington, D.C., 14 May 2019 (PAHO)- Seasonal influenza, also known as flu, is an illness that can lead to serious complications requiring hospitalization and can even cause death. People often fail to recognize its severity, mistaking it for a cold, but each year around 772,000 people are hospitalized, and between 41,000 and 72,000 die as a result of influenza in the Region of the Americas.

Vaccination is the most effective way to prevent serious complications. Although there is a moderately effective vaccine — given the constant changes in circulating viruses that make it necessary to annually update its composition—it is estimated that only half of the at-risk population gets vaccinated each year in the countries of the Region that report data.

In an article published in PAHO’s latest Immunization Newsletter, which has been distributed globally for 40 years, experts from the Pan American Health Organization (PAHO) explain the myths and truths about influenza and the flu vaccine.

Vaccinating patient against the flu

Myth 1: The flu is like a cold. FALSE

Seasonal influenza is characterized by initial symptoms of high fever, cough, chills, muscle and joint pain, and headache. It can cause severe complications that require hospitalization and can even cause death. Colds are caused by other viruses, with symptoms such as runny nose, scratchy throat and perhaps a little fever.

Myth 2: Influenza can be a very serious, mortal illness. TRUE

Certain population groups are more at risk of complications from influenza (pregnant women, children under the age of 5, the elderly, health workers, and people with chronic diseases such as diabetes, and pulmonary and heart diseases), but children and young people with no risk factors can also have complications. Studies show that patients hospitalized with influenza who have not been vaccinated are two to five times more likely to die than those who have been previously vaccinated.

Health care workers are at greater risk of infection and transmission due to their contact with patients. This is why vaccination is crucial for this group.

Myth 3: The vaccine can cause influenza. FALSE

Influenza vaccines have been used for decades. They are safe and cannot cause influenza. Neither of the two types of existing vaccines—the injection containing inactivated viruses, or the nasal spray vaccine made from live (attenuated) viruses—can cause the disease. It takes the body about two weeks after being vaccinated to be protected, and during this time a person may be infected by influenza or other respiratory viruses that can cause flu-like symptoms, leading them to mistakenly believe that they contracted influenza from the vaccine.

Myth 4: Adverse events related to the vaccine are serious. FALSE

As with any vaccine or medication, there are adverse events associated with the influenza vaccination. However, the most common vaccine-related side effects are mild: mainly pain and redness at the injection site.

Myth 5: The flu vaccine is not effective. FALSE

The effectiveness of the vaccine (in terms of the protection it offers) tends to be moderate (around 40-60%) and changes every year. It depends on age, health condition, and how well the viruses used for the vaccines match those that are circulating. Vaccination of pregnant women is essential to protect their babies, since the vaccine is not recommended in children under 6 months old.

In the 2017-18 season in the United States, the vaccine prevented an estimated seven million illnesses, 109,000 hospitalizations, and 8,000 flu-related deaths. Furthermore, the evidence suggests that if a person is vaccinated against the flu and still becomes infected, the disease will be less serious than if they had not been vaccinated—that is, it will prevent complications, hospitalization, or even death.