Undervaccination linked to increased pertussis risk

UNDERVACCINATION with the diptheria, tetanus toxoids and acelluar pertussis (DTaP) vaccine appears to be associated with an increased risk of pertussis (whooping cough) in children 3 to 36 months of age, according to a study* by Institute for Health Research at Kaiser Permanente Colorado, Denver.

Children undervaccinated for three or four pertussis vaccine doses are 18 to 28 times more likely to contract the infection, commonly known as whooping cough.

Kaiser Permanente researchers used the Vaccine Safety Datalink – a collaborative effort among the Centers for Disease Control and Prevention and eight managed care organizations – in this study to analyze the immunization records of 323,247 children born between 2004 and 2008. Seventy-two patients with laboratory-confirmed cases of pertussis, commonly referred to as whooping cough, from this group were compared to four times as many children of the same age and gender who were not infected with whooping cough.

The diptheria, tetanus toxoids, and acelluar pertussis (DTaP) vaccine protects against whooping cough. It is given in a series to children at two months, four months, six months and 15-18 months of age and as a booster before kindergarten.

 “Undervaccination is an increasing trend that potentially places children and their communities at an increased risk for serious infectious disease,” according to the study.

The study involved children born between 2004 and 2008 and cared for at eight managed care organizations. Each child with laboratory-confirmed pertussis (72 patients) was matched to four randomly selected control patients for a total of 288 controls.

Undervaccincation was defined as missing any of four scheduled doses of the DTaP vaccine. Of 72 case patients with pertussis, 34 (47.22%) were undervaccinated for DTaP vaccine by the date of pertussis diagnosis compared to 64 (22.2%) of the control patients.  Children undervaccinated for three or four doses of DTaP vaccine were 18.56 and 28.38 times more likely, respectively, to have received a diagnosis of pertussis than children who were age-appropriately vaccinated, the study reports. 

"A growing number of parents are choosing to have their children follow alternative vaccination schedules," said lead study author Jason Glanz, Ph.D., a senior scientist at at Kaiser Permanente's Institute for Health Research. "Recent whooping cough outbreaks have raised concerns that undervaccination may place children at risk for serious infectious diseases. The findings of this study indicate that those concerns have merit. Children, and the larger community, are more likely to contract these types of diseases if they are not vaccinated according to recommended guidelines."

Pertussis is a highly contagious bacterial disease that causes uncontrollable, violent coughing and can be deadly in infants, especially those under two months of age who are too young to be fully vaccinated. In 1976, there were just over 1,000 reported cases of pertussis in the U.S. By 2012, it climbed to 41,880 cases. The DTaP vaccine has been shown to be 98% effective in preventing whooping cough.

“Undervaccination with DTaP vaccine increases the risk of pertussis among children 3 to 36 months of age,” the study concludes.

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