Current whooping cough vaccine less reliable than its predecessor

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This week, scientists in Australia reported in the Journal of the American Medical Association that children given the DTaP — the current vaccine used to prevent whooping cough — were four times more likely to contract whooping cough than children given the DTwP, which is an older version of the vaccine. The DTwP was found to still be effective in preventing whooping cough ten to twelve years after vaccination.

Whooping cough, or pertussis, is a highly contagious bacterial infection of the respiratory tract that can cause severe illness or death, particularly in infants younger than two months old, which is when the fist DTaP vaccination is recommended. There has been a sharp increase in the number of whooping cough cases in the United States. More than 20,000 cases have been reported so far in 2012, while only 8,500 were reported in all of 2011. The suspicion that the current vaccine is less effective, combined with the fact that there is a strong anti-vaccination movement in the US, may help explain the sharp increase in cases.

When the whooping cough vaccine was first introduced in the 1940s, it cut the number of cases from over 200,000 a year to just a few thousand a year in the 1970s. In order to combat the possible side effects of DTwP (which could range from mild pain and swelling to — more rarely — neurological problems), scientists developed the DTaP in the 1990s.

The vaccine schedule currently recommended is for children under the age of seven to receive the DTaP series, and then a booster of TDaP when they are 11 or older. A study done by Kaiser Permanente Vaccine Study Center in Oakland, California, determined that while the DTaP was 90% effective immediately after vaccination, it was less than 50% effective five years later.

The Centers for Disease Control and Prevention are going to study the issue of DTaP’s waning effectiveness, and will determine if earlier or more frequent TDaP booster shots are needed to maintain immunity. Adults should also receive the TDaP in order to protect against the loss of effectiveness of the DTaP over time and to protect those around them who may be vulnerable to whooping cough.

Sources: NPR, American News Report, Kaiser Permanente