An early start to the 2026 flu season brings with it many questions and misconceptions about vaccines, medication, and other respiratory illnesses such as COVID-19.
The Centers for Disease Control recently reported that the percent of positive influenza tests for the week of October 5 was 10 times higher than during the same period last year.
To separate fact from fiction, we spoke with Connor McKittrick, MD, senior instructor of family medicine in the University of Colorado Anschutz School of Medicine.
True or myth: Getting a flu vaccine mean you won’t get the flu.
Myth. This is not necessarily true, McKittrick says. Influenza vaccines are typically 40%-60% effective at preventing people from contracting the flu.
“This variability is due to the mutation potential of the influenza virus year over year and the fact that multiple strains of influenza can spread throughout the same year that may not be a great match for the influenza vaccine components for the year,” he says.
“The influenza vaccination is designed yearly to protect against three main groups of Type A and B influenza virus strains that tend to make people sick,” McKittrick continues. “The vaccine virus components that are selected for each year’s formulation are selected based on year-round flu virus surveillance from over 150 national influenza centers in more than 120 countries.”
True or myth: If you do get the flu after getting vaccinated, the vaccine has no effect on the severity or duration of symptoms.
Myth. Studies show that even when individuals contract influenza despite receiving the influenza vaccination, the risks of severe influenza-associated outcomes are significantly decreased, McKittrick says.
“A 2026 systematic review/meta-analysis published in Clinical Microbiology and Infection found that receiving the influenza vaccination leads to decreases in hospitalization rates by 42%, ICU admissions and intubation/ventilator support needs by 51%–55%, and death by 36%,” he says.
McKittrick counsels patients on the benefit of influenza vaccinations “not only on decreasing the risks of contracting the flu, but also on decreasing rates of influenza-associated severe outcomes even if they were to contract the flu despite receiving the influenza vaccination.”
True or myth: A flu vaccine can give you a false positive on a flu test.
This one is sort of true, McKittrick says — it depends on which influenza vaccination is administered. Injectable intramuscular vaccinations, which are either inactivated/killed vaccines or recombinant vaccines, have no live influenza components and do not cause false positive results.
“However, intranasal influenza vaccinations, which are attenuated, meaning the influenza virus within the vaccine is modified to make it significantly weaker and unable to cause serious illness but still trigger a protective immune response, can produce a false positive influenza test by detecting the vaccine virus rather than a true separate influenza virus infection,” he says. “Generally, virus shedding from the intranasal vaccine can last from two to 10 days and can be detected during this time frame.”
True or myth: You cannot have the flu and another respiratory illness, like COVID-19, at the same time.
Myth. You absolutely can have multiple respiratory illnesses at the same time, especially during respiratory season — fall, winter, and early spring — when influenza and COVID strains are circulating higher throughout the community, McKittrick says.
True or myth: Tamiflu only works if you take it within two days of symptom onset.
Generally true. Tamiflu (oseltamivir) works by inhibiting an enzyme called influenza neuraminidase, McKittrick says. This enzyme is found in the influenza virus and is responsible for releasing new viral particles from our own infected cells. By blocking this enzyme, Tamiflu limits viral spreading and allows our immune system a better chance to destroy the virus. Ideally, patients should start taking Tamiflu within two days of symptom onset to limit progression.
“It is important to block the replication/spread cycle of influenza while it is in the early stage of infection and still actively spreading, as this will help limit the severity of infection,” McKittrick says. “By starting within two days, individuals in the general population can shorten their illness duration by one to two days and up to three days in adults over 65 and those with chronic medical conditions. There can be a role for post-exposure prophylaxis with Tamiflu in asymptomatic high risk patient populations, and I encourage patients to discuss this with their medical providers if they have had exposure to influenza and think they would qualify.”
True or myth: Tamiflu negates the effects of a flu vaccine.
Myth. “Tamiflu does not interfere with your immune system’s antibody response to the vaccine,” McKittrick says. “If someone develops an influenza infection and has received the influenza vaccination, it is safe and generally recommended to take Tamiflu.”
