Study: Infants most likely to catch whooping cough from siblings

Study: Infants most likely to catch whooping cough from siblings
Study: Infants most likely to catch whooping cough from siblings

A new study from the Centers for Disease Control and Prevention (CDC) suggests that infants most commonly catch pertussis from their siblings. The research, published online in the journal Pediatrics, is in contrast to previous studies that found mothers to be the main source of transmission.

“Knowing where they are getting their disease from is important so we can target our approach accordingly,” lead author Tami H. Skoff, an investigator with the CDC, told Reuters Health.

Pertussis – also known as whooping cough because of the sound patients make while gasping for air – is a highly contagious and potentially fatal respiratory disease, occurring most frequently in infants and children. It can be a prolonged illness – lasting up to 10 weeks in some – and can be especially dangerous to babies under one year of age. In 2012 there were 20 pertussis-related deaths, the majority of which were infants younger than 3 months.

Although overall the number of reported cases of whooping cough was down from 2012 figures, CDC researchers reported an increase in pertussis cases in teens 13 through 16 years of age in 2013 and 2014. To determine if the infant source of infection was linked to the increase in teen infections, Skoff and her colleagues analyzed data collected between 2006 and 2013 from 1,306 infant whooping cough cases in seven states.

Study results showed a change in transmission pattern that raises concerns about how we protect against pertussis. The findings revealed that 66.6 percent of cases were passed on by family member. The researchers found that 35.5 percent of the cases came from siblings, 20.6 percent originated from mothers, and 10 percent stemmed from fathers.

According to the researchers, mothers were the main source of infection for infants until 2008. Given that whooping cough is becoming more common in older children, Skoff and the research team were not surprised by the new findings.

“It makes sense that we are seeing this transition from mothers to siblings as the source of infection,” Skoff said.

Another reason for the shift, noted the study authors, is the switch in the 1990s from the traditional whooping cough vaccine to the newer one. Known as DTaP, the new vaccine was developed out of concerns about rare neurological problems tied to the older vaccine. The only problem is that the new vaccine doesn’t last as long.

“The vaccine is very effective in the short term,” Skoff told HealthDay. However, the CDC estimates that whooping cough immunity slowly weakens each year after the child’s final dose at age 5.

And that points to another issue: Kids who have been vaccinated and come down with whooping cough may not be very sick and unknowingly pass the disease to an infant, who is at greater risk for becoming severely ill. Of babies younger than 1 year who get whooping cough, half require hospitalization, according to the CDC.

Skoff advised that the best way to protect infants from pertussis is for mothers to get a whooping cough booster – known as Tdap – during the third trimester of pregnancy. The vaccine has proven to be safe, she said, and infants are born with some of the mother’s immune system antibodies, which would offer short-term protection until they are old enough to get their first DTaP shot.

“You are providing direct protection to the mom and direct protection to the infant,” Skoff explained.


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