Polio
Although people rarely think of polio any more and some think that it has already been eradicated, there were just over 2,000 cases of polio around the world in 2006. Most cases are now concentrated in just a few countries, including Nigeria, India, Pakistan, and Somalia.
Before the polio vaccine began to be used in 1955, polio outbreaks were common in the United States too though. Polio is caused by a virus and although many children who become infected don't develop any symptoms, about 1 in 200 who are infected develop paralytic polio. Many of these children have a permanent disability and 5 to 10% do not survive.
During regular outbreaks in the United States, there were up to about 21,000 cases of paralytic polio each year. Parents feared polio so much that swimming pools and playgrounds used to be closed during summers when there were epidemics.
Mass immunization campaigns in the few remaining countries where polio is a problem and continued immunization in all other parts of the world should soon mean that the goal of eradicating polio is a reality.
Rubella
Rubella is also known as German measles or "three day measles" and unlike most of the other vaccine preventable infections, this viral disease is usually pretty mild. In fact, many people with rubella don't even have any symptoms. The rest have lymphadenopathy (swollen glands), a rash, and low grade fever that typically lasts for three days.
If rubella is so mild, then why do we need a rubella vaccine?
The main reason is that up to 80% of babies who are born to mothers who have rubella during their first trimester of pregnancy often develop congenital rubella syndrome, with an increased risk of miscarriage. These babies are usually born with many birth defects, including cataracts, deafness, glaucoma, heart defects, hepatitis, low birth weight, mental retardation, microcephaly (a small head), and thrombocytopenic purpura (low platelet counts in their blood).
During a rubella outbreak in 1964 to 1965, there were about 20,000 cases of congenital rubella syndrome. Rubella is now rare in the United States since the introduction of the rubella vaccine in 1969 (it is a part of the MMR vaccine), but is still a problem in the rest of the world, with over 250,000 cases in 2006.
Tetanus
Most parents associate tetanus with "lockjaw" and needing a tetanus shot if you step on a rusty nail.
Infection in newborns (neonatal tetanus with an infected umbilical stump) used to be the most common type of tetanus infections, and was quite serious, as up to 95% of the babies died. These infections were already on the decline when the tetanus vaccine was introduced in 1938 though, because of improved delivery conditions and hygiene.
Tetanus is caused by toxins produced by the Clostridium tetani bacteria. Spores of the C. tetani bacteria are commonly found in soil and in the intestines of many animals. The spores can easily contaminate cuts, scrapes, and other wounds -- especially dirty wounds.
Unlike all other vaccine preventable illnesses, tetanus is not contagious.
Good hygiene and continued vaccination with the tetanus vaccine (the T in the DTaP and Tdap vaccines) has lead to low levels of tetanus in the United States. It is still a big problem around the world though.
