The bacteria for diphtheria are present in the eye, nose, and throat discharge of an infected person and are spread by close contact with another person. It is very unlikely that your child will ever be exposed to this disease because there is now only an average of five cases per year in the United States.
Tetanus is unique because it is the only vaccine preventable illness that cannot be spread from person to person. The bacteria are found in the soil and are spread to humans when dirt enters a break in the skin. Thus, the likelihood of contracting tetanus is entirely related to the number of dirty wounds your child experiences and how those wounds are managed. Appropriate care of wounds with extensive washing is important in preventing your child’s exposure to tetanus.
While tetanus is not common in the United States, it is a significant cause of death internationally.
Worldwide, tens of thousands of infants die every year from neonatal tetanus. We still have vivid memories of seeing newborn children die from tetanus when we was practicing in Africa during our training. These infections could be prevented by immunizing pregnant women. After the mothers developed appropriate antibodies, they would pass them on to their children as part of the maternal transfer of antibodies that occurs late in pregnancy. If the babies had some antibodies at birth, they might be better able to fight off neonatal tetanus.
Pertussis is spread by droplets from coughing. Unfortunately, it is easy to spread the infection. First, infected individuals are contagious for two to six weeks. Second, the infection starts out mildly and does not seem serious at first, so the antibiotics that would stop the spread of the infection are delayed. Some research suggests that up to 80 percent of unimmunized household members will develop the disease.
As for your particular child, it depends on how common pertussis is in your community. Epidemics occur every two to five years in many communities. This is probably because the immunity wanes in adolescents and adults and they can be reinfected, starting the infection cycle all over again.