How Effective Is the Flu Shot in an ‘Off’ Year?

Out of nowhere, you feel like you got hit by a truck. Your body aches, and though your temperature is skyrocketing, you can’t pack on enough blankets to ease up those teeth-rattling chills. You know the feeling.

Flu can really knock you on your ass, and in some cases, it can even be deadly. That’s why experts recommend you get the flu shot each season, which can start up as early as October and end as late as May. (One thing: the flu infects your lungs, nose, and throat. Suffering from a puking-and-pooping bug instead? Check out Your Stomach Flu Survival Guide.)

The flu shot can help prevent the flu or decrease its severity. But this year, that prick is not be as protective as you might think.

Your Flu Shot Might Not Be Effective This Year

By November 2014—“early” flu season—about 31 percent of adults ages 18 to 49 rolled up their sleeves for a shot, according to Centers for Disease Control and Prevention (CDC) estimates. The problem with this year’s season, though, is that the vaccine may not be doing a whole lot of good.

A new report from the CDC found that so far this season, the flu shot was only 23 percent effective. That means that people who were vaccinated were 23 percent less likely to see their doctor because of the flu than their unvaccinated peers.

If that sounds low to you, it’s because it is: For each of the previous two seasons, early or interim estimates of the effectiveness of that year’s vaccine hovered around 60 percent. In fact, over the last 10 years, there was only one season that wrapped up worse than where we are right now.

Why Is This Year Different?

To understand what went wrong with this year’s vaccine, we need to take a look at how the shots are manufactured. In February of each year, experts select three or four flu strains that research suggests will be the most common the next season. Typically, they’re the ones that circulate the most during that time.

Then the vaccines are manufactured—most often, they’re grown and replicated in eggs. Then they’re prepared and purified before they can be used.

The whole process can take about 6 months from when the viruses are first chosen to when the vaccines are shipped out. And that’s the problem.

The type of flu that’s causing such a problem this season is a particular H3N2 strain—a mutated version that wasn’t yet around when the manufacturing of the vaccine first began last February.

“The influenza viruses are always changing, but for one to appear kind of late in the season, and then to quickly become the predominant virus, that may be related to the particularly low effectiveness of this year’s vaccine,” says Brendan Flannery, Ph.D., an epidemiologist with the CDC.

In this case, the virus probably underwent several mutations that left it quite different from the strain included in the vaccine, he says. As a result, our immune responses to that vaccine don’t end up protecting ourselves very well to that virus.

If You Haven’t Gotten Pricked, Should You Still Get the Shot?

The short answer: yes. That’s because even though effectiveness is low, vaccination still can prevent some infections, as well as reduce the risk of severe sickness or hospitalizations, says Flannery.

What’s more, we’re not even close to done with flu season. According to CDC data, flu season most often peaks in February.

And as the season progresses, different strains tend to circulate more. In particular, as flu season winds to a close, that’s when the B strains tend to pop up. Experts believe that those strains may be more closely matched with what was in this year’s vaccine.

“That’s one of the reasons we still recommend that people who haven’t gotten vaccinated do get vaccinated,” said Flannery. “We hope that the vaccine will prevent more of the influenza B infections if we do have a second wave or if we have a late wave of influenza B viruses.”

How Can You Feel Better, Faster?

The mutated H3N2 strains mean that more people who got the flu shot are actually coming down with the flu than in previous years. So what can you do if you’re among the unlucky ones?

First, don’t write off the flu just because you got the shot. If you feel yourself coming down with symptoms like fever, headache, cough, aches, and chills, get in touch with your doctor.

Your doc can write you a prescription for antiviral drugs, such as Tamiflu or Relenza. Antiviral drugs work by attacking an important part of the flu virus called neuraminidase, says Flannery. This stops the virus from replicating, which can prevent you from getting sicker and shorten the duration of your symptoms.

These drugs work best if they’re started within 48 hours of feeling sick. So if you notice the symptoms come on, don’t try to wait them out before getting your doctor involved.

And if you’re considered “high risk,” antiviral treatment can be especially important, says Flannery. That includes people with chronic lung conditions like asthma, chronic heart conditions, and metabolic conditions like diabetes.

You can also help reduce flu symptoms similar to how you’d treat a cold: That means getting a lot of rest, drinking enough fluids, and taking OTC pain meds like Advil or Tylenol to reduce fever and pain. (Check out The Cheat Sheet for OTC Pain Pills to see which might work best for you.)

What Does This Mean for Future Flu Seasons?

It’s uncommon for flu vaccines to provide as little effectiveness against the H3N2 viruses as they’re doing this year, says Flannery.

But the flu viruses are always changing, which means it’s possible that another mutated strain could arise next year, too.

The way flu vaccines are made now is a 6-month endeavor, so it misses out on including late-season game-changers in the mix. The solution down the line, then, may be a whole new process.

“Right now, the part of influenza that changes so much is exactly the part that our immune system recognizes and we put into vaccines,” says Flannery.

So researchers are now looking into developing a vaccine that isn’t dependent on that evolving part. This would be known as a “universal” vaccine. The good thing about it is that you wouldn’t necessarily need to get the shot each year.

But don’t get too excited: More research is needed, and its potential clinical implications are still years down the road.