The Influenza virus changes all the time and travels around the world so fast that it is difficult to track, contain or control. Luckily, under most circumstances the 'flu' does not threaten your life. Other infectious diseases cause greater harm and can even kill. In fact, more people die from infectious diseases than from any other cause. While our bodies naturally defend themselves against harmful microbes, they can not win every battle.
Some microbes are just too strong or too numerous.
So we have had to be resourceful in combating disease. One of the means we have developed is vaccination, which builds up the body's defenses against disease before the disease attacks the body. Vaccinations are particularly important for infants as they are more vulnerable to the harmful effects of a disease. Through vaccination campaigns, one major disease, smallpox , has been eradicated and another, polio , is expected to be eradicated by the year 2000. B ecause of these advances , it seemed for a while as if we might be winning the struggle against disease.