Here’s a deck of 100 cards.

How it works

The deck is a model of how a flu season can go for you. The proportion of flu cards in the deck represents the chance that an adult your age who isn’t vaccinated gets sick with flu in a typical season: 10 flu cards out of 100 means about a 10% chance. Counts are rounded to whole cards.

Age	Flu cards, unvaccinated	Flu cards, vaccinated
18–49	10	6
50–64	15	9
65+	8	5

A typical season. How many flu cards each age gets, and the hospital and death odds on the back of each card, come from CDC’s estimates of flu illness, hospitalization, and death by age, averaged over 13 seasons from 2010–11 to 2024–25. The two COVID-19 seasons are excluded. CDC’s rates are averages across everyone, including the many people who got vaccinated, so they understate the risk for someone who isn’t vaccinated. We scale CDC’s rates up to estimate the risk for unvaccinated people, using each age group’s vaccination rate and the vaccine’s typical effectiveness, following the method CDC uses to estimate the illness prevented by vaccination.

Sick with flu means symptomatic flu illness as CDC estimates it, which counts everyone who gets sick with flu, including people who never see a doctor. CDC says flu usually comes on suddenly, with fever or chills, body aches, and fatigue, and most people recover in a few days to less than two weeks. People with flu can spread it starting about a day before they feel sick.

Hospital stays and deaths. For people of each age who get sick with flu, the chance of a hospital stay (counting those who die there) and the chance of dying come from the same CDC estimates. Older adults get sick with flu less often than younger adults, but far more of them end up in the hospital or die when they do.

Age	Chance of ending up in the hospital, if you get flu	Chance of dying, if you get flu
18–49	about 1 in 180	about 1 in 5,200
50–64	about 1 in 94	about 1 in 1,500
65+	about 1 in 11	about 1 in 100

The vaccine prevents about 40% of flu illness, so the wizard replaces about 40% of the flu cards with blank ones. That is the median of CDC’s season-by-season estimates of how well the vaccine prevents flu illness serious enough to see a doctor, since 2010–11. It works better some years than others: CDC’s estimates have ranged from 19% to 60%, depending on how well the vaccine matches the flu strains going around that year. The deck uses the same effectiveness at every age, which is a simplification. The standard vaccine produces a weaker immune response in older adults, which is why CDC prefers high-dose, adjuvanted, or recombinant flu vaccines at 65 and older.

If you get flu anyway. Vaccinated people who get flu may have a milder illness. In studies of adults hospitalized with flu, vaccinated patients were less likely to need intensive care or to die, but these are observational studies: people who get vaccinated also tend to be healthier in other ways, and the studies can’t fully separate the two. The flu cards that remain after the swap are drawn a little less menacing to show this.

Free for most people. Most insurance plans cover the flu vaccine with no copay at an in-network provider, and Medicare Part B pays for it in full. The $15 Walgreens offer is a store promotion for myWalgreens members (free to join), not available in every state.

Caveats. Real seasons vary widely, from mild to severe. The deck shows an average season, not a forecast for this one or a personal risk estimate. Some chronic conditions, such as asthma, heart disease, diabetes and a weakened immune system, raise the risk of serious flu at any age, as does pregnancy.

To see the same numbers play out across 10,000 adults, try the flu season simulation.