Studies have shown that vaccine-preventable disease levels are at or near record lows. Despite the fact that most infants and toddlers have received all recommended vaccines by age 2, many under-immunized children remain, leaving the potential for outbreaks of disease. Many adolescents and adults are under-immunized as well, missing opportunities to protect themselves against diseases such as Hepatitis B, influenza, and pneumococcal disease; or these adolescents and adults forget to update their vaccinations.

The reason for outbreaks in this day and age is often due to lack of opportunity for people to receive immunizations and when those who receive them don't maintain a schedule in keeping them up to date.

So what is a vaccine? Whenever a disease-causing microorganism enters the body, the immune system mounts a defense, producing proteins to fight off the foreign substance. Vaccines stimulate the body's immune system by introducing a weakened form of a particular germ or virus, making the body think it is being invaded by a foreign organism. If a person who has been vaccinated is later exposed to the virus, he or she will be protected because the body already has the necessary antibodies to ward off infection.

The problem not updating your vaccinations occurs in situations when the virus changes form, which is very common with the flu or influenza virus.

Influenza, a virus that targets the respiratory tract by binding to the surface of cells, weakens the immune system, making the body vulnerable to more serious infections, such as pneumonia. Influenza viruses are like chameleons in that they are constantly changing the patterns on their outer surface to avoid being targeted by antibodies. This rapid mutation rate is the reason seasonal flu vaccines must be changed annually. Each year, world health authorities create a flu vaccine that protects against three types of seasonal flu -- two subtypes of type A flu and one subtype of type B.

Another important vaccine is for pneumococcal pneumonia. This vaccine is recommended if you fall under the following criteria:

-65 years old or older

-Have a serious long-term health problem such as heart disease, sickle cell disease, alcoholism, lung disease (not including asthma), diabetes, or liver cirrhosis

Your resistance to infection is lowered due to; HIV infection or AIDS, Lymphoma, leukemia, or other cancers, Cancer treatment with x-rays or medicines, Treatment with long-term steroid medicines. Bone marrow or organ transplant, Kidney failure or kidney syndrome.

-Damaged spleen or no spleen

-You are an Alaskan Native or from certain Native American populations

Medical authorities also recommend that all babies and children younger than 2 years old get the pneumococcal vaccine.

Pneumococcal pneumonia can infect the upper respiratory tract and can spread to the blood, lungs, middle ear, or nervous system. Pneumonia can be caused by a variety of viruses, bacteria, and sometimes fungi and is caused by bacteria called Streptococcus pneumoniae. Pneumococcus is spread through contact between people who are ill or who carry the bacteria in their throat. You can get pneumococcal pneumonia from respiratory droplets from the nose or mouth of an infected person. It is common for people, especially children, to carry the bacteria in their throats without being sick.

Symptoms include high fever, cough, shortness of breath, rapid breathing, and chest pains.

The pneumococcal vaccine is the only way to prevent getting pneumococcal pneumonia.

Another important vaccine is the herpes zoster of shingles. This vaccine was approved and released in May 2006 and reduces the risk of shingles in people ages 60 years and older. Shingles, which is caused by the varicella-zoster virus, is the same virus that causes chickenpox. After an attack of chickenpox, the virus lies dormant in certain nerve tissue. As we age, the virus can reappear in the form of shingles. Shingles are often characterized by clusters of blisters that can cause severe pain that may last for weeks, months, or years.

Shingles also often cause a rash on one side of the body, the left or right. The rash appears in a band, a strip, or a small area. Shingles is most common in older adults and people who have weak immune systems because of stress, injury, certain medicines, or other reasons. Most people who get shingles will get better and will not get it again.

There is no cure for shingles, this is why doctors are recommending the vaccination for those qualified candidates.

Last is the Hepatitis B vaccination, which is recommended for all infants, older children and adolescents who were not vaccinated previously, and adults at risk for HBV infection.

Hepatitis B is a disease caused by the hepatitis B virus, a virus that infects the liver and causes inflammation. Originally known as "serum hepatitis", the disease has caused epidemics in parts of Asia and Africa, and it is endemic in China. About a third of the world's population, more than 2 billion people, have been infected with the hepatitis B virus.

Transmission of hepatitis B virus results from exposure to infectious blood or body fluids containing blood. Possible forms of transmission include (but are not limited to) unprotected sexual contact, blood transfusions, re-use of contaminated needles