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Are you being nudged to get your flu shot? If you’re a healthy young adult who takes care of yourself, you may think you are naturally protected from the flu. In a recent survey by Student Health 101, nearly all students who responded (96 percent) said they believe that healthy lifestyle choices will help protect them from flu infection this season. Is this true?

Only to a relatively minimal degree. Healthy behaviors serve us very well in many ways—but they cannot substitute for a flu vaccine. It’s tempting to believe otherwise, because we are routinely subjected to inaccurate and misleading messages about how immunity works. You have probably come across claims that a particular food product or dietary supplement can “boost” your immune system. Few of these claims are backed by evidence. What they boost instead is our false sense of protection against a common and contagious virus. The flu is at best an inconvenience that disrupts students’ academic performance, extracurriculars, and relationships. At worst, it’s a serious and life-threatening disease, even to some young, otherwise healthy adults.

ExposureExposure to the flu is almost inevitable

“There’s nothing you can do to resist the flu besides getting vaccinated,” says Dr. Paul Offit, professor of vaccinology and professor of pediatrics at the University of Pennsylvania School of Medicine.

“You can not go outside, you can stay by yourself in your room, you can live in a protective bubble.  But if you enter the world, you’re going to be exposed [to influenza viruses]. You can’t avoid getting infected just by having a healthy immune system, although it will give you the best chance of fighting a disease. And you’re not going to have natural immunity before you’ve been exposed.”

It’s true that if we are chronically stressed out, exhausted, or malnourished, our immune function probably won’t be as good as it could be. “Does this increase our chance of getting severely infected? Yes,” says Dr. Offit.

BoostWhy we can’t “boost” our immune system

It may seem intuitive that if we can lower our immunity by becoming physically and emotionally run-down, we can also strengthen it by taking care of ourselves. Surprisingly, that doesn’t follow—at least, not in the ways we might expect.

While healthful habits help us in all sorts of ways, they cannot equip us with the antibodies that could fight off a specific virus. Reasonably healthy people already have normal immune function, and this is not “boosted” by taking extra care of ourselves.

“There’s no going above normal,” says Dr. Ben Kruskal, chief of infectious diseases at Harvard Vanguard Medical Associates /Atrius Health, Boston. “You can only fill your gas tank as full as it gets. If you pay a bit more for fancy gas that will maybe give you slightly better mileage or speed. But it can’t turn your Toyota into a racecar.”

AntibodiesHealthy habits don’t generate antibodies

The scientific highlights the unique role of vaccines. “What we know now is that [healthy behaviors like] good diet and good sleep are not enough to prevent all illnesses. Influenza and other vaccine-preventable infections are good examples. If the immune system has not seen a particular infection before, it cannot mount the high-quality, fully protective immune responses needed for protection,” says Dr. Timothy Lahey, associate professor of medicine and associate professor of microbiology and immunology at the Geisel School of Medicine, Dartmouth College, New Hampshire.

“Sure, it helps not to be malnourished, but a good diet is no substitute for an effective vaccine. The influenza epidemic of 1918 is a great example: The highest rates of mortality and morbidity occurred among young healthy people who, unlike their elders, had no immunological memory of that strain of influenza [because their immune systems had not encountered it before] and therefore perished in droves.”

VaccineHealthy behavior + vaccine = protection

“Fortunately, in 2015 people with good common sense do not need to choose between a healthy diet and the miracle of vaccines,” says Dr. Lahey.

“Good diet and sleep [help] prevent illnesses, and so they are good to get. To add to that protection, vaccines can stave off lethal infections like influenza, measles, tetanus, and human papillomavirus, which can afflict even the most well-fed and well-rested person.”

Flu virus

Can you get the flu from the flu shot?

You will likely hear people say the flu vaccine gave them the flu. It can look that way, but they are mistaken. Here’s how we know this for sure:

  • The viruses in the flu shot have been killed. They can’t make copies of themselves, so they can’t make people sick.
  • The nasal spray form of the flu vaccine is live and weakened so that it can’t cause infection. The viruses cannot reproduce at body temperature, survive in the lungs, or cause the flu.

Here’s why some people may get sick after a flu shot:

  • They may have a bad cold or another respiratory illness.
  • They may have been infected by a flu virus that wasn’t in the vaccine.
  • They may have been exposed to a flu virus shortly before or after getting vaccinated; it takes up to two weeks for the vaccine to become fully effective.

Can you get the flu from a bird or pig? 
Influenza viruses are constantly mutating (evolving), “so there are lots of opportunities for drastic changes,” says Dr. Carlton-Smith. In certain circumstances, flu viruses can mutate in ways that enable them to transmit from birds or animals to humans. Still, that source of infection is unlikely. “If you work on a swine farm or have a bird coop on your roof, you should be careful about touching the animals’ mouths or noses, and wash your hands well,” says Dr. Kruskal.

Do sleep & stress management protect us from the flu?

Does stress management protect us from the flu?

De-stressing offers limited protection against the flu
It is important for many reasons to manage our stress. But in terms of susceptibility to the flu, the benefits of stress management are difficult to measure and are probably pretty small.

“The worst personal and academic stress—your girlfriend broke up with you, your grandmother just died, you’re failing your classes—may mean you are maybe 5 percent more likely to get sick enough from the flu that it keeps you from your normal activity, like going to class or a party,” says Dr. Kruskal.

Stress management is extremely valuable for our health and wellbeing. For strategies, check out Stress & the student body in this issue. Stress management does not substitute for a flu shot.

Does sleep protect us from the flu?

Adequate sleep offers little protection against infection 
The extent to which our sleep determines our susceptibility to infection is probably relatively small, says Dr. Kruskal. “If you want to protect your house against termites, it helps that it is structurally sound with a good paint job and no cracks. But those do not protect against termites in the way that an anti-termite spray treatment does.” For humans, getting adequate sleep is necessary, part of being structurally sound—but that does not in itself protect us from the (viral) invasion.

That said, sleep can affect your immune function
Chronic sleep deprivation is a state of extended stress that appears to impact immune function and general health, according to a 2012 study in the European Journal of Physiology. But we don’t really know how that works. Scientists have a lot to learn about how sleep protects our health in general. “We all believe good sleep is critical to good health, and there are some illnesses like hypertension that are known to be more frequent among people with chronically bad sleep. In time the mechanisms will be worked out, but to date many remain the stuff of conjecture,” says Dr. Lahey.

Sleep is vital for our health and wellbeing. It does not equip us with flu virus antibodies, however, so it cannot substitute for a flu shot.

Do exercise & healthy eating protect us from the flu?

Does physical activity protect us from the flu?

Physical activity offers little protection against infection 
“There’s no really good data on how and whether physical activity protects against infection. It may have a small effect,” says Dr. Kruskal. “Imagine a SWAT team in peak physical condition. Let’s say you work out consistently, you’re very muscular, you eat and sleep well. Those habits are not going to substitute for body armor if someone shoots you.” Of course, those healthy habits serve us very well in other ways. (Student Health 101 is naming Dr. Kruskal our expert consultant in analogy.)

That said, physical activity may affect the immune system 
Physical activity is another excellent way to cope with stress, and exercise seems to affect the immune system in direct ways too, according to the National Library of Medicine. There are theories about how this works, but no conclusions yet. For example, exercise raises body temperature, and maybe that makes life uncomfortable for some disease organisms. (Fever is believed to be helpful in this same way.) But again, don’t count on your workouts for flu protection.

Physical activity is a powerful medicine and essential for our health and wellbeing. It does not substitute for a flu shot.

Does healthful eating protect us from the flu?

Healthful eating offers limited protection against infection 
“Eating a very, very healthy diet will not give you better immunity than if you eat a reasonably healthy diet,” says Dr. Kruskal. Again, if your immune system is functioning normally, you can’t “boost” it.

If you’re malnourished, that’s different
“Malnourishment is clearly associated with vulnerability to a variety of diseases, for instance tuberculosis. It stands to reason, then, that maintaining a healthy diet can help prevent or ameliorate infections and other illnesses as well,” says Dr. Lahey. Again, the data are limited about how that works. Most of us are not malnourished, so we won’t be taking that immunity hit in the first place.

Eat healthfully anyway 
You know the drill: lots of fruits and vegetables, whole grains, and moderate amounts of the right kinds of fats and proteins (favor plant-based sources over animal-based). Don’t overdo highly processed foods, as these tend to be high in sugar, saturated fats, and salt.

Healthful eating is a gift to our bodies and great for our health and wellbeing. Nevertheless, it does not provide flu antibodies.

What’s missing from alternative treatments and lifestyle practices?

Alternative treatments and practices probably won’t help 
Can alternative medicine and lifestyle practices help your immune system resist infection? Although some practitioners say yes, the vast majority of such claims are not supported by evidence. For example, there is no evidence that massage therapy, detox cleanses, or eating organic can improve our immunity.

The homeopathic treatment Oscillococcinum is sometimes cited as a flu remedy, but an analysis of multiple studies in Cochrane Database Systematic Reviews (2004) concluded that the evidence isn’t there.

Yoga and meditation 
Yoga, meditation, and biofeedback are associated with a physiological relaxation response. “Again, the studies are small and not rigorously designed. We don’t have enough information on whether these practices offer any protection against infectious or chronic disease,” says Dr. Kruskal. These practices can be very helpful for other reasons, of course.

Some alternative treatments and lifestyle practices may help you feel good. They do not serve as a flu shot.

What are the side effects of the flu shot?

“The flu shot is incredibly safe, and has been shown time and time again to confer protection against a lethal disease. Yet generally well-meaning people decline it and other measures designed to keep our most fragile citizens safe from harm,” says Dr. Lahey.

Some people have a mild reaction to the flu vaccine. Here’s what that can look like:

  • The flu shot can cause pain and redness at the injection site and sometimes a low fever. 
  • The nasal spray sometimes causes mild upper respiratory symptoms, like sniffles.

Allergic to eggs? Modern flu vaccines won’t cause symptoms. Although the vaccine development process involves eggs, these days there is no risk of contamination.

How contagious is the flu? (and other basics)

“I’ve got the flu” is not just another way of saying “I feel rotten.” There are lots of reasons for feeling rotten. The flu—influenza—is a specific disease caused by a particular group of viruses. The flu is not the same as the common cold (which can also feel horrible).

Influenza is very contagious. If you have the flu, you can pass on the virus to half the people you come in contact with. Every year, up to 20 percent of people in the US get the flu.

You can catch the flu virus in four ways:

  1. Via droplets in the air from infected people coughing or sneezing around you
  2. By handling something previously handled by an infected person (e.g., a doorknob).
  3. By putting your mouth on something that someone infected has touched with their mouth (e.g., drinking from the same cup, taking a bite of their sandwich).
  4. By direct contact, such as kissing or shaking hands.

You get sick pretty quickly after you’ve been exposed to the virus, usually within four days. Other people can catch the flu from you before you even realize you’re sick.

The flu makes some people very sick. Every year hundreds of thousands of Americans are hospitalized and 30,000 die. That can include young, otherwise healthy people.

If you have the flu:

  • You will feel miserable for a week or even two
  • You will probably have a high fever
  • Your head and body will ache
  • You will have a cough, sore throat, and a stuffed-up nose
  • You may vomit or have diarrhea

Which is better for us: the vaccine or natural exposure?

There are only two sure ways to reduce your risk of getting the flu:

  1. Get vaccinated:  The annual flu vaccine is safe. It stimulates your immune system to produce antibodies to the three or four flu viruses that are likely to be predominant this season. Ask at your student health center.
  2. Get the flu: You’ll be miserably sick for a week or two. In 2014, about one in six undergraduates said that having a cold, sore throat, or the flu had damaged their academic performance (National College Health Assessment survey). But the flu virus, like the vaccine, will produce antibodies that will protect you against being re-infected by the flu virus that made you sick.

“The vaccine provides the same immunity that’s induced by natural infection without your having to pay the price of natural infection,” says Dr. Offit. “‘Natural’ is not always good. Smallpox is natural.”

“I hope there will be a time that we can be informed consumers of health care products, and connect logic instead of fear-mongering to our decisions about good interventions like flu shots. I get one every year and feel no qualms about it,” says Dr. Lahey.

The flu vaccine is far safer and more convenient than natural flu infection. Getting vaccinated in general is one of the most effective—and easiest— behaviors that protect and nourish our health.

What’s wrong with vitamin supplements and “natural” flu remedies?

Vitamin supplements do not protect us from infection 
Do not fall for the hype. “You can put yourself in the best position possible by making sure you eat healthy, etc., but when you walk into GNC and buy a vitamin that says it boosts immunity, I think that’s largely nonsense,” says Dr. Offit. “If this industry was regulated by the FDA (the US Food and Drug Administration), they wouldn’t be on the shelf.”

And manufacturers may regret their claims to the contrary 
In 2008, the manufacturers of Airborne, a vitamin and herbal supplement that had been marketed as “boosting” the immune system and improving germ resistance, agreed to refund $23.3 million to consumers as a penalty for their false advertising. “There’s no credible evidence that what’s in Airborne can prevent colds or protect you from a germy environment. Airborne is basically an overpriced, run-of-the-mill vitamin pill that’s been cleverly, but deceptively, marketed,” said David Schardt, a senior nutritionist from the Center for Science in the Public Interest (CPSI).

Vitamin supplements do not substitute for a flu shot. Should you take them for other reasons? Probably not. Increasing evidence suggests that for most of us, vitamin supplements are a waste of money and may even do more harm than good. (For people on certain restrictive diets, vitamin supplements may be necessary.)

Can you get the flu despite the flu shot?

How the flu vaccine works 
There are hundreds of strains of influenza. New strains of the flu emerge frequently, and existing strains can become more or less common in our environment. That’s why scientists develop a new flu vaccine every year. It is designed to protect people against the three or four strains of influenza that are expected to be most common in the upcoming flu season. That selection is based on data assembled from World Health Organization influenza centers globally.

How much difference does the flu vaccine make? 
The predictions are usually accurate. The flu shot is on average 60 percent effective, says the Centers for Disease Control and Prevention (CDC). “Flu vaccines are always useful even if they are not as effective as hoped,” says Dr. Charles Carlton-Smith, a research fellow specializing in virology and immunology at Massachusetts General Hospital. Here’s why:

  • The flu vaccine may stimulate the immune system to recognize similar flu strains to those in the vaccine (this is known as cross-strain protection).
  • The vaccine can take up to two weeks to become fully effective. If you are exposed to the flu in this period, your symptoms will likely be milder than they would have been without the vaccine.
  • The immunity you receive in this year’s flu vaccine may help protect you against flu infection in future years.

Why the flu vaccine is not infallible 
The most common circulating flu virus in the 2014–15 flu season was under the radar when the vaccine was being developed, so the vaccine was not designed to protect against it. That’s why last year’s vaccine was less effective than usual.

Solve the Outbreak

By the Centers for Disease Control and Prevention (CDC)

Sonya Mendoza

Sonya Mendoza: Third-year undergraduate at Northern Illinois University majoring in biological sciences; Student Health 101 Student Advisory Board 2015-16.

“It’s a problem-solving game. The player collects information, analyzes data, and solves the case, which is about finding the cure for deadly diseases and ultimately saving lives.”

Not everyone is looking to get into medicine, but this app helps students become well informed on real-life scenarios in an engaging way. 
Rating: 4/5 stars

Since hypothetical zombie outbreaks are in these days, the CDC’s realistic game is a refreshing way to experience what’s behind the scenes.
Rating: 5/5 stars

I’m a biology major with no set idea on what I want as a career, but the idea of being a disease detective is now catching my interest.
Rating: 4/5 stars

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Tabitha M Powledge, MS, is a science and medical journalist who has written for dozens of consumer and professional publications. She is founding editor of The Scientist, author of The Complete Idiot’s Guide to Microbiology, and writes On Science Blogs for the PLOS Blog Network.