What Signals the Start of Flu Season?
Oct 02, 2017
One might think that flu season starts with the arrival of vaccine in the local pharmacy or provider’s office. Others might believe that flu season in the U.S. begins with the first case of lab verified flu. While flu viruses are most common during the fall and winter months, influenza activity can begin as early as September or October and last as late as May.
The CDC monitors certain key flu indicators (like outpatient visits of influenza-like illness, lab results and reports of flu hospitalizations and deaths). When these indicators rise and remain elevated for a number of consecutive weeks, than “flu season” is said to have begun.
In preparation for flu season, the Centers for Disease Control and Prevention (CDC) and the National Foundation for Infectious Diseases (NFID) kick off their annual flu vaccine campaign each September with a special press conference which emphasizes the importance of flu vaccination.
The reality is that influenza is difficult to predict. No one knows when it will peak, how many people will suffer or die, or even how effective the flu vaccine will be.
However, what experts do know is that the flu is inevitable, yet preventable. Every year there is suffering, hospitalizations and even deaths, but much of that could be prevented if more people were protected through annual vaccination.
Flu is a fickle and unpredictable virus.
This was the message Dr. Bill Schaffner delivered during the news conference last week. Since 2010, flu-related hospitalizations in the U.S. typically range from 140,000 to 710,000 each year, killing between 12,000 and 56,000 people each year. While the exact number may differ drastically from year to year, this just highlights how dangerous and unpredictable influenza is.
Now is the ideal time to get a flu shot. You want to be vaccinated weeks before possible exposure, because it can take about two weeks post-vaccination for your body to build the proper immune response from the vaccine.
Everyone should consider flu vaccination – even healthy individuals.
The flu vaccine is recommended for everyone 6 months and older. It not only helps to reduce the risk of flu illness and serious complications for the person getting vaccinated, but it also helps to reduce the amount of flu circulating in the community. By reducing the incidence of flu, we can help protect those who might be more susceptible to serious flu illness, such as young infants too young to get vaccinated, pregnant women and older individuals who may be more susceptible to flu infection, and individuals with certain medical conditions, like heart disease, asthma and diabetes, who are at increased risk of complications from flu.
Too often people mistakenly believe that if they are healthy they don’t need a flu vaccine. Or, they don’t realize how dangerous the flu can be and consider it akin to a bad cold. However, influenza is a contagious respiratory illness with no cure. Once the virus takes hold, all we can do is treat the symptoms. While antiviral drugs are recommended to try to lessen symptoms and shorten the time one is stick by a day or two, the reality is that influenza must run it’s course. This is why Dr. Northrop could do nothing but watch while his otherwise healthy adult sister succumbed to influenza and died.
Why choose vaccination if it can’t guarantee you won’t get flu?
We often hear people explain that they won’t get a flu shot because it doesn’t guarantee that they won’t get the flu. While it is true that the flu vaccine isn’t a 100% guarantee, the annual flu vaccine is typcially about 40-60% effective. Therefore, getting your annual flu vaccine means you will reduce your chances of getting the flu by 40% to 60% as compared to someone who does not get vaccinated. It also means that flu vaccination can significantly reduce the risk of flu-associated hospitalization and death (especially among children and older adults).
As an example, last year’s flu vaccine effectiveness was deemed to be approximately 42% effective overall. While that may not sound overly impressive, it is estimated that flu vaccination last year prevented about 5.4 million cases, 2.7 million flu-related doctor’s visits and 86,000 hospitalizations last season. But last year only about 46.8% of the U.S. population 6 months and older received a flu vaccine. Now imagine if more people had been vaccinated. The CDC estimates that if overall flu vaccination coverage had been just 5 percentage points higher, another 490,000 illnesses and 7,000 hospitalizations could have been prevented.
What determines flu vaccine effectiveness?
There are a lot of factors that can determine vaccine effectiveness – such as a person’s individual immune response (or lack of immune response in some cases), the type of vaccine they received, when they received it, whether the vaccine was properly handled in transit and in storage, as well as whether the vaccine they received contained the strains that became the most prevalent strains throughout the season. However, even a vaccine that is just 40% effective has the ability to reduce the amount of circulating influenza. (For more information about flu vaccine effectiveness, check the CDC website here.)
For the record, there is no way a flu vaccine can actually give you the flu.
Inactivated flu vaccine viruses have been “killed” and include only broken up parts of the inactive virus. Therefore, the flu vaccine cannot cause the flu. However, since it takes about two weeks after vaccination for antibodies to develop in response to the vaccine, it is still possible for an individual to get the flu or another respiratory virus during that time. They may have even been exposed prior to getting vaccinated.
While some people may experience symptoms such as fever, muscle pain, general discomfort or weakness after receiving a flu vaccine, these side effects typically last 1-2 days after vaccination and are much less severe than actual flu illness. If you were to have influenza, your symptoms would be more severe and would likely last a full 5-7 days. Even if you were to get the flu after being vaccinated, it’s likely that your symptoms would be less severe, which could reduce the risk of hospitalization or death.
This is why the CDC recommends people get vaccinated early in fall, before flu season begins, and preferably by the end of October, if possible. Getting vaccinated later, in the flu season, even into January, can still be beneficial as flu viruses have been known to circulate into May. By why wait?
What do we need to know about this year’s flu vaccine?
For the 2017-2018 flu season, the CDC recommends injectable influenza vaccines such as an inactivated influenza vaccine or recombinant influenza vaccines. Once again, nasal spray flu vaccine – also known as live attenuated influenza vaccine or LAIV – is not recommended for use this season. To learn more about which vaccine options are available for the 2017-2018 season, click here.
Flu vaccines are only as useful as the society that takes advantage of them.
Last season’s overall vaccination rate of about 46.8% is pretty typical. But in analyzing the data we can see that even small increases in vaccination rates can make a big impact. For instance,
- Flu vaccination coverage in children last year – a year where we lost 106 children to flu – was about 59%. Sadly, most of the children who died were otherwise healthy and unvaccinated. However, a study in the journal Pediatrics, showed how flu vaccination reduced the risk of flu-associated death by nearly 65% in healthy children and 51% in children with underlying high-risk medical conditions. If we could raise childhood vaccination rates we could save lives.
- Flu vaccination coverage among older individuals increased last year, but was still only about 45.4% among people 50 and older, and 65.3% among adults 65 and older. Since these adults are at greater risk for more severe complications due to flu, getting older family members and nursing home residents could make a significant impact.
- Flu vaccination coverage among pregnant women hovers around 50% from year to year, but flu vaccination is known to protect both a woman and her baby both during and after pregnancy. One study found that flu vaccination in pregnancy reduced the risk of flu-associated acute respiratory infection by about 50%. There are even studies that show that flu vaccine in a pregnant woman can reduce the risk of flu illness in her baby by up to 50% as well. And this protective benefit was observed for up to four months after birth. What expectant mother wouldn’t want to help protect her baby in this way? We simply must do a better job at communicating these benefits to pregnant women.
- Of course, flu vaccination is critical for people who already suffer with chronic health conditions, and studies have shown that vaccination can reduce hospitalizations among people with diabetes by 79% and chronic lung disease by 52%.
- A study in Clinical Infectious Diseases showed that flu vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among adults hospitalized because of influenza.
There are plenty of reasons to get a flu shot and a sufficient supply of flu shots available.
If you haven’t received your annual flu shot yet, check the Flu Vaccine Finder and make a plan to get yourself and your family members vaccinated before the flu finds it’s way into your community.
For more information about flu vaccines, check out these resources:
- CDC Flu Information
- Frequently Asked Flu Questions 2017-2018 Influenza Season
- To view a recording of the CDC/NFID press conference, click here. To read a transcript of the news conference, click here. For more vaccine coverage data from last season (2016-2017), see the online summary report.
Note: This content originally appeared in Vaccinate Your Family’s Immunization Alerts e-newsletter, sent March 31, 2021. You can sign up for future alerts on our website. April 9, 2021: An update was made to...
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