December 9, 2019

Some Flu Seasons Are Worse Than Others

Here’s Why — And What You Can Do About It


It’s December, which means more than half the country is in the middle of a dangerous game of flu roulette. That’s because less than half of Americans get the flu vaccine. Last year was one of the longest flu seasons ever, and it came on the heels of one of the worst flu seasons in recent memory, which broke records for the number of flu-related deaths and illnesses. Still, despite known risks and personal encounters with the nasty virus, most people don’t protect themselves. 
Even though there’s no such thing as winter without a flu outbreak, flu season inevitably catches people off guard — especially those who choose not to get a flu shot. On the other hand, it’s hard for people who consistently get the flu shot to appreciate the impact it has on their health — and the health of those around them. No one can know if they were among the 50% who avoided the flu because of the vaccination, or if they got a milder, less miserable case because their body already had some built-in defense. It’s also hard to quantify herd immunity and the individual role we each play in keeping the flu from those who can’t be vaccinated. Can one person really make a difference? The short answer is yes, when we realize that community is the sum of a lot of individuals.

Here’s a look at the factors that influence the severity of flu season each year and several things you can do to help minimize the flu’s impact.

  1. The strain of the flu. Every February, the U.S. Food and Drug Administration (FDA) determines which three or four flu strains to include in the next vaccination, and that triggers the production of vaccines for the following fall. In 2017-2018, the dominant strain was H3N2, which is known to cause more serious illnesses and tends to be less responsive to vaccination than other strains. Last year, the dominant strain was H1N1, which is more easily addressed by the flu shot and leads to less severe illness. The truth is that some years the prevalent virus strain is more potent and harder to fight with a vaccination. Regardless of the strain, those who get a flu shot will likely fare better than those who go unprotected.
  2. The number of people who get a flu shot. No matter how you look at it, the flu vaccine prevents millions of cases each year. During the 2017-2018 season, the vaccine prevented an estimated 7.1 million flu illnesses, 3.7 million medical visits, 109,000 hospitalizations and 8,000 deaths. It was the worst season we’ve seen in decades, but without the flu shot, it would have been even more catastrophic. Even still, only four in 10 adults were vaccinated that year, and it marked the lowest vaccination levels at every age group compared to the previous seven seasons. The following year, early season vaccinations rose by 7% — most likely out of fear — which helped to minimize the number of cases during the 2018-2019 season.
  3. Misconceptions about what constitutes an “effective” vaccination. Some people who get a flu shot and still get sick are quick to label the vaccination as ineffective, when it’s much more complicated than that. Many people who get sick with the flu would have gotten a lot sicker without a vaccination. For example, adults with the flu are 80% less likely to be admitted to the ICU. Flu vaccinations have also been tied to a lower incidence of cardiac events in people with heart disease, and they reduce the risk of flu-associated acute respiratory infection in pregnant women by half, in addition to protecting newborn babies from the flu in their first few months when they are too young to get a shot. It’s hard for a lot of people to grasp, but the effectiveness of the flu shot is about much more than whether or not you get the flu.
  4. The effectiveness of the current vaccination. Two factors influence the effectiveness of a flu vaccine: the age and health of the recipient and the match between the circulating flu virus and the vaccine. Every February, the FDA reviews flu data and determines the strains to include in the vaccination for the following season. Anticipating the most prevalent flu strains can be challenging, especially when there is a late-season strain that peaks after production for the next year has begun. This year, scientists updated last year’s vaccination to make an even better match against the H1N1 and H3N2 strains that are already circulating, and early indications show it’s a good match. When the flu vaccine mirrors circulating flu viruses, the vaccine reduces the risk of getting sick by about half. It’s important to understand, however, that even in years like 2017-2018 when the vaccine is not a good match, the effectiveness is typically around 40%.

There is no doubt that flu vaccinations directly influence the severity of the flu each season. The math is simple: If more people get vaccinated, fewer people get sick. If fewer people are sick, there’s less flu virus to spread, which reduces population illness rates dramatically.  Generally, everyone older than six months should get a flu vaccination, with rare exceptions for those with allergies, illness and specific chronic conditions. If you haven’t gotten your flu shot, it’s not too late. Protect yourself and your family today, and do your part to avoid a dangerous flu outbreak this season!