I haven’t gotten a flu shot EVER and I haven’t gotten any other shots other than tetanus once every 15 years or so in 35+ years.   I also haven’t had the flu in at least 15 years — unlike many people who get the flu vaccine and then get sick.
Dr. Mercola wrote at Pregnant Nurse Fired for Refusing Flu Shot:

Nurse Fired by Placing Baby’s Safety First…

… The nurse, Dreonna Breton, who has already had two miscarriages, told her employer she did not want to get a flu shot this year due to the potential risks to her baby, noting the lack of vaccine safety studies done in pregnant women. She submitted letters from both her obstetrician and primary care doctor in support of her decision, and offered to wear a mask throughout the flu season.
Personnel exempted from the flu vaccine due to religious reasons typically wear masks, and it’s an effective way to protect both yourself and your patients not only from influenza but other flu-like respiratory infections as well.
Her employer disagreed, however, and told her she’d be fired as of December 17 if she didn’t get vaccinated before then. A spokesman for Horizons Healthcare Services told CNN that “it’s unconscionable for a health care worker not to be immunized.”
This responsible pregnant mother did her research, and subsequently rejected a pharma product. The hospital administration at Horizons Healthcare Services fired her for this. If you would like to express your unhappiness with the hospital, as well as your commitment to not going there and telling others not to as well, we encourage you to do so. ….

I called Horizons and the operator also got her flu shot.  When I asked why, she offered to take my info down and promised that somebody would get back to me.  I’ll update if that happens, which is unlikely.
Here are Dr. Mercola’s recommendation on flu prevention and staying healthy:

Guidelines for Natural Flu Prevention

It’s important to remember that your immune system is your primary line of defense against any virus, so keeping your immune function high should be at the top of your list if you want to avoid influenza or other flu-like illness. The following guidelines can help keep your immune system in optimal working order so that you’re far less likely to acquire the infection to begin with or, if you do get sick with the flu, you will be better prepared to move through it without complications and soon return to good health.

  • Optimize Your Vitamin D levels. As I’ve previously reported, optimizing your vitamin D levels is one of the absolute best strategies for avoiding infections of ALL kinds, and vitamin D deficiency may actually be the true culprit behind the seasonality of the flu – not the flu virus itself. This is probably the single most important and least expensive action you can take. Regularly monitor your vitamin D levels to confirm your levels are within the therapeutic range of 50-70 ng/ml.Ideally, you’ll want to get all your vitamin D from sun exposure or a safe tanning bed, but as a last resort you can take an oral vitamin D3 supplement. According to the latest review by Carole Baggerly (GrassrootsHealth.org), adults may need as much as 8,000 IUs a day.
  • Avoid Sugar/Fructose and Processed Foods. Sugar impairs the function of your immune system almost immediately, and as you likely know, a healthy immune system is one of the most important keys to fighting off viruses and other illness. Be aware that sugar (typically in the form of high fructose corn syrup) is present in foods you may not suspect, like ketchup and fruit juice.
  • Optimize Your Gut Flora. The best way to do this is avoid apply the step above by avoiding sugars, processed foods and most grains, and replacing them with healthy fats and taking regular amounts of fermented foods, which can radically improve the function of your immune system
  • Get Enough Rest. Just like it becomes harder for you to get your daily tasks done if you’re tired, if your body is overly fatigued it will be harder for it to fight the flu. Be sure to check out my article “Guide to a Good Night’s Sleep” for some great tips to help you get quality rest.
  • Have Effective Tools to Address Stress. We all face some stress every day, but if stress becomes overwhelming, then your body will be less able to fight off the flu and other illness. If you feel that stress is taking a toll on your health, consider using an energy psychology tool such as the Emotional Freedom Technique, which is remarkably effective in relieving stress associated with all kinds of events, from work to family to trauma.
  • Get Regular Exercise. When you exercise, you increase your circulation and your blood flow throughout your body. The components of your immune system are also better circulated, which means your immune system has a better chance of finding an illness before it spreads. Be sure to incorporate high-intensity interval exercises like Peak Fitness into your routine.
  • Take a Good Source of Animal-Based Omega-3 Fats. Increase your intake of healthy and essential fats like the omega-3 found in krill oil, which is crucial for maintaining health. It is also vitally important to avoid damaged omega-6 oils that are trans fats and in processed foods as it will seriously damage your immune response.
  • Wash Your Hands. Washing your hands will decrease your likelihood of spreading a virus to your nose, mouth or other people. Be sure you don’t use antibacterial soap for this – antibacterial soaps are completely unnecessary, and they cause far more harm than good. Instead, identify a simple chemical-free soap that you can switch your family to.
  • Tried and True Hygiene Measures. In addition to washing your hands regularly, cover your mouth and nose when you cough or sneeze. If possible, avoid close contact with those who are sick and, if you are sick, avoid close contact with those who are well.
  • Use Natural Immune Boosters. Examples include oil of oregano and garlic.
  • Avoid Hospitals. I’d recommend you stay away from hospitals unless you’re having an emergency and need expert medical care, as hospitals are prime breeding grounds for infections of all kinds. The best place to get plenty of rest and recover from illness that is not life threatening is usually in the comfort of your own home.

Common sense.  And I suppose that’s how I’ve avoided the flu in so many years.