Why do we hear that every year? There are a few reasons why every flu season could be the worst. One is that the vaccine for the flu is based on a projection (you could call it a guess) of what viral strains we might be exposed to in the upcoming winter season. The problem is that it is hard to guess (project). So one can get the vaccination and still get the flu, because the actual strain is different from the projected strain that the vaccine was supposed to fight.
Another reason is that more and more people are traveling on airplanes to more and more destinations. Airline travel is a major transmission vector for flu viruses. One way to avoid getting sick on a plane is to coat the insides of your nasal passages with almost any edible oil before taking off. Put the oil on cotton swabs and store them in a plastic bag to use when you get on the plane. The oil prevents your nasal passages from drying out and cracking from the air conditioning on the plane during the flight. Viruses can enter cracked nasal passages and gain entry to your body—keeping them coated will help prevent that.
Another interesting reason for more flu viruses could be attributed to antibiotics, which are often given for flu upper respiratory infection– even though they were designed for bacterial infections. In a 2017 joint Harvard and MIT study published in the journal Cell Host and Microbe, it was shown that antibiotics reduce the ability of immune cells to kill bacteria. This logically leads one to ask if antibiotics impair the immune system in general and if they may also lead to more viral infections and upper respiratory infections in general. Also, research studies have shown that antibiotics can impair the immune response to viruses after they are administered.
The best defense against a flu virus turns out to be a healthy immune system. If your immune system is healthy then it can outperform any vaccine or antibiotic. These therapies were designed for people whose immune systems cannot perform to their full potential.