National Infant Immunization Week is April 23-30 this year. This week, the History of Vaccines blog features posts about several diseases that can be prevented by vaccination of infants.
Although its name is not as well known as those of diseases like chickenpox or measles, rotavirus is the most common cause of severe diarrhea in children and infants worldwide. Before a vaccine was introduced in the United States, the disease caused more than 400,000 doctor visits and 200,000 emergency room visits each year, causing as many as 60 deaths annually in U.S. children younger than five. Globally, rotavirus kills more than 500,000 children each year, with most deaths in developing countries.
The virus spreads easily among children, and can also be passed from children to those with whom they’re in close contact. Rotavirus spreads via the fecal-oral route — that is, from the waste of an infected person to the mouth of another individual. This can occur via contamination on hands or objects like toys.
Rotavirus can be prevented by vaccination, with the first dose of the vaccine series recommended at two months of age. Efforts are also being made to make rotavirus vaccine available throughout the developing world. Mexico was one of the first countries to receive rotavirus vaccine in 2006; by the 2009 rotavirus season, death rates from diarrheal disease had dropped in both the target population for vaccination (children younger than 11 months old, where the rate dropped by 40%) and among children between one and two years of age (by almost 30%). The fact that death rates dropped even in a part of the population that is not targeted by the vaccine suggests that herd immunity benefited the unvaccinated inviduals: with fewer infections to begin with, the disease circulated less in the population, leaving less opportunity for exposure.
Contrary to the lesser-known rotavirus, pertussis (or as it’s more commonly called, “whooping cough”) has once again become a common source of concern, primarily because of the widespread 2010 California outbreak. The disease is caused by the Bordetella pertussis bacterium, although as with other bacterial diseases like diphtheria, the bacterium itself isn’t the cause of illness. Instead, it secretes a toxin that paralyzes parts of respiratory cells, causing inflammation in the respiratory tract. The end result and most widely known symptom is a bout of rapid coughing followed by the characteristic “whooping” sound that gives the disease its common name. Coughing fits can last as long as two and a half months, sometimes even longer; pertussis is sometimes called the “100-day cough.”
More than half of children younger than one year of age who catch pertussis require hospitalization; globally, the disease causes about 300,000 deaths each year.
Pertussis can be prevented by vaccination. The first dose of the five-dose vaccine series (DTaP, which also protects against diphtheria and tetanus) is recommended at two months of age. Adults are also recommended to receive a booster Tdap dose (tetanus, diphtheria, and pertussis) vaccine every 10 years, as immunity from the vaccine is not lifelong.