HEPATITIS B: A serious viral disease that affects the liver.

ROTAVIRUS: Causes severe diarrhea, mostly in babies and young children. It is often accompanied by vomiting and fever.

DIPHTHERIA: A bacterial disease that causes a thick covering in the back of the throat. It can lead to breathing problems, paralysis, heart failure and even death.

TETANUS: Also known as lockjaw, the bacteria cause painful tightening of the muscles, usually all over the body. Tetanus leads to death in up to two cases out of 10.

PERTUSSIS: The bacterial disease, also known as whooping cough, causes severe coughing spells, vomiting and disturbed sleep. It can lead to weight loss, incontinence, rib fractures and passing out from violent coughing, pneumonia and hospitalization due to complications. In 2004, there were more than 25,000 cases of pertussis in the United States.

HAEMOPHILUS INFLUENZA B (HIB): A bacterial disease that usually strikes children younger than 5. It's spread from person to person and can cause serious illness if it lodges in the lungs or bloodstream. Before HIB vaccine, the disease was the leading cause of bacterial meningitis (infection of the brain and spinal cord covering) among children younger than 5, sometimes causing lasting brain damage and deafness.

PNEUMOCOCCAL INFECTIONS: A serious bacterial illness that is responsible for about 200 deaths each year among children younger than 5. Before a vaccine was available, pneumococcal infection caused more than 700 cases of meningitis, 13,000 blood infections and about 5 million ear infections each year.

INFLUENZA: The flu virus spreads from infected persons to the nose or throat of others. Can cause high fevers and seizures in children.

MEASLES: Caused by a virus that results in rash, cough, runny nose, eye irritation and fever. It can lead to ear infection, pneumonia, seizures, brain damage and death.

MUMPS: A viral disease marked by fever, headache and swollen glands. It can lead to deafness, meningitis, painful swelling of the testicles or ovaries, and, rarely, death.

RUBELLA: Also known as German measles, it's a virus that causes rash, mild fever and arthritis (mostly in women). If a woman gets rubella while she is pregnant, she could have a miscarriage or her baby could be born with serious birth defects.

VARICELLA: Commonly known as chickenpox, varicella is usually mild but can be serious, especially in young infants and adults. It causes a rash, itching, fever and fatigue, and it can lead to severe skin infection, scars, pneumonia, brain damage or death. Before the vaccine, about 11,000 people were hospitalized for chickenpox each year in the United States.

HEPATITIS A: A serious liver disease caused by a virus, HAV, that is usually spread by close personal contact and sometimes by eating food or drinking water containing HAV.

MENINGITIS: A serious bacterial illness caused by infection of the fluid surrounding the brain and spinal cord. Meningococcal disease also causes blood infections. About 1,000-2,600 people get meningococcal disease each year in the United States, killing 10 percent to 15 percent. Of those who survive, another 11 percent to 19 percent lose their arms or legs, become deaf, have problems with their nervous systems, become mentally retarded or suffer seizures or strokes.