What is diphtheria?

Short Answer

There are two types of diphtheria: respiratory (which affects the lungs and breathing tubes) and cutaneous (affecting the skin). It’s caused by a bacterium that is spread through direct person-to-person contact with the discharge from an infected person’s nose, throat, or skin, or through contaminated food or objects. Respiratory diphtheria symptoms include a low-grade fever, with a grayish “coating” on the tonsils, pharynx, or inside the nose. Cutaneous diphtheria causes infected skin lesions that can look different from person to person. Diphtheria is fatal for as many as one in five children. The diphtheria vaccine is 97% effective in preventing the disease, with booster shots needed every 10 years to maintain immunity.

Source:

http://www.cdc.gov/vaccines/vpd-vac/diphtheria/fs-parents.html

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002575/

http://www.cdc.gov/vaccines/vac-gen/side-effects.htm

Symptoms & Incubation
Symptoms begin to appear two to five days after coming in contact with the bacteria, and can include:
• Bluish coloration of the skin
• Bloody, watery drainage from nose
• Breathing problems
• Grayish coating on the tonsils, pharynx, or inside the nose
• Chills
• Croup-like (barking) cough
• Drooling (suggests airway blockage is about to occur)
• Fever
• Hoarseness
• Painful swallowing
• Skin lesions (usually seen in tropical areas)
• Sore throat (may range from mild to severe)
Complications
The grayish coating on the throat can get so thick that it blocks the airway, preventing the person from breathing.
The diphtheria toxin can attack the heart, causing abnormal heart rhythms and even heart failure. It can also attack the nerves, which leads to paralysis.
About one out of 10 people who get diphtheria dies. In children younger than 5 years, as many as one out of five children who get diphtheria will die.
Transmission
Diphtheria spreads through respiratory droplets (such as those produced by a cough or sneeze) of an infected person or someone who carries the bacteria but has no symptoms. Diphtheria can also be spread through contaminated objects or foods (such as contaminated milk). In warm climates, skin lesions tend to contribute more to disease transmission. A person can spread the disease for up to two weeks after infection.
High-risk Populations
Sporadic cases are more likely to occur among adults whose immunity has weakened. Children are less likely to become infected because of sustained high vaccine coverage for children in the U.S. Unvaccinated or inadequately vaccinated people who travel to countries where diphtheria is endemic are at increased risk.

Vaccine
The DTaP vaccine combines the vaccines for diphtheria and two other serious diseases: tetanus and whooping cough (pertussis). The vaccine helps the body to build up protection against the diphtheria toxin. Most children (about 97 children out of 100) who get all doses of the vaccine will be protected against diphtheria.
Safety & Side Effects
The DTaP vaccine is very safe, and it is effective at preventing diphtheria, tetanus, and whooping cough. Vaccines, like any medicine, can have side effects. But severe side effects from the DTaP vaccine are very rare.
Mild side effects are seen in about one quarter of children and include fever, and redness, swelling, and/or tenderness at the injection site. These discomforts occur more often after the fourth and fifth doses of the DTaP series than after earlier doses.
Sometimes the fourth or fifth dose of DTaP vaccine is followed by swelling of the entire arm or leg in which the shot was given, for one to seven days (up to about one child in 30).
Other mild side effects include fussiness (up to about one child in three), tiredness or poor appetite (up to about one child in 10), and vomiting (up to about one child in 50). These problems generally occur one to three days after the shot.
More uncommon, moderate side effects include seizure (about one child out of 14,000) and high fever of 105 degrees Fahrenheit or higher (about one child out of 16,000).
Schedule
Children should get five doses of the DTaP vaccine at the following ages for best protection:
• One dose each at 2 months, 4 months, and 6 months;
• A fourth dose at 15 through 18 months; and
• A fifth dose at 4 through 6  years of age.

It is safe to get the DTaP vaccine at the same time as other vaccines, even for babies.
A diphtheria booster is needed every 10 years after the fifth childhood dose, to extend protection through adulthood.
Since the Vaccine Was Introduced…
Before the diphtheria vaccine, there were about 100,000 to 200,000 cases of diphtheria each year in the U.S. As many as 15,000 people died each year from the disease. Cases dropped quickly after the vaccine. While there hasn’t been a case of diphtheria in the U.S. since 2003, it’s still prevalent in other countries.