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SWIFTWATER, Pa. -- A new study released today in the April issue of Pediatric Infectious Disease Journal about the transmission of pertussis -- commonly known as whooping cough -- found that household members were the source for 71 to 82 percent of cases among infants for whom a source case could be identified. The study demonstrates the importance of vaccination of close contacts of infants to reduce the number of infant pertussis cases and potentially save lives.
The study, the first simultaneous evaluation of infant pertussis conducted in four countries [including the United States], was led by researchers at the University of North Carolina, Chapel Hill (UNC-CH) and was supported by sanofi pasteur, the vaccines business of the sanofi-aventis Group. This study was conducted over a 20-month period and found that, among infants with pertussis for whom the source could be identified, parents were the source of 55 percent of cases, followed by siblings (16 percent), aunts/uncles (10 percent), friends/cousins (10 percent), grandparents (6 percent), and part-time caregivers (2 percent). In previous studies, identifying the source of infection was hindered by incomplete case data and less comprehensive laboratory evaluation of contacts.
Pertussis is a highly contagious bacterial infection. The disease is spread though airborne droplets that are transmitted when an infected person coughs or sneezes.Â It may start with symptoms similar to a mild cold or a dry cough that persists and eventually worsens. The infected person may look and feel healthy between episodes of coughing. If left untreated, pertussis can be spread for several weeks. At particular risk are newborns who have not been vaccinated or fully vaccinated against the disease. They are more vulnerable to severe pertussis and face the possibility of serious complications and even death.Â In fact, more than 90 percent of pertussis deaths have occurred in infants.
While pertussis cases in all age groups have been rising, it is important to know how the disease is spread, particularly to infants who are too young to be vaccinated themselves, so that steps can be taken to prevent infections in these vulnerable infants and potentially save lives, said Annelies Van Rie, MD, assistant professor of epidemiology in the UNC School of Public Health. It is troubling to learn that infants are often infected with pertussis by their own family members, who are often unaware of having pertussis themselves.
The number of reported cases of pertussis has been rising across the United States, heightening concern in the public health and medical communities. This is partly because pertussis immunity from early childhood vaccinations eventually wears off, leaving adults and adolescents susceptible to the disease. The most current data from the United States Centers for Disease Control and Prevention (CDC) indicate that the number of pertussis cases increased between the 1980s and 2005. While the number of cases increased in all age groups, reports of pertussis have increased most dramatically among adolescents and adults. Most adolescents and adults are not diagnosed with pertussis because they frequently have milder disease.
The Advisory Committee on Immunization Practices (ACIP) of the CDC now recommends that adults and adolescents be given a tetanus-diphtheria-pertussis booster (Tdap) in place of the tetanus-diphtheria (Td) booster to reduce the burden of pertussis in this country. Since 2005, Adacel vaccine has offered pertussis protection for individuals 11 through 64 years of age, and is currently the only pertussis booster vaccine for both adolescents and adults in the United States.
Ongoing research, such as this study, demonstrates that adolescents and adults can transmit pertussis to infants and that pertussis immunization of adolescents and adults would not only have an effect on their own health, but would also protect young infants from pertussis. said Van Rie. Those who have an infant at home or who come into contact with infants at work should be immunized against pertussis.