Whooping Cough Vaccine Loses its Effectiveness, Study Says

The whooping cough (pertussis) vaccine losses efficacy over time, according to a new study. A worrying fact given some prior outbreaks involving the dangerous bacteria.

In fact, said the LA Times, California saw a massive outbreak in 2010 that left about 1,000 sick in Los Angeles alone, sickened 9,000 state-wide. Now, nationally, we are expected to see the largest pertussis caseload in over 50 years.

The emerging study, just published in the New England Journal of Medicine, was conducted by researchers at the Kaiser Permanent Vaccine Study Center in Oakland. The team reviewed the data of 277 who tested positive for the whooping cough bacteria between 2006 and 2011. These data were compared with over 3,000 children who tested negative and another 6,000 matched controls, said The LA Times.

The study suggests that outbreaks are erupting with greater frequency because the DTaP shot—the vaccination that protects against whooping cough—decreases in efficacy following the fifth and last recommended dose, which is typically received when children are five years of age, explained The LA Times. As we’ve explained, whooping cough is a highly infectious condition marked by an unstoppable urge to cough.

The research revealed that, compared with the controls, those children who developed pertussis had received their fifth dose earlier. The team concluded that for each year following the fifth dose, the DTaP vaccine drops in efficacy by 42%, said The LA Times.

This means, explained the team, if the DTaP vaccine starts out with 95% efficacy—a figure The LA Times described as the group’s most optimistic estimate—that efficacy will fall to 79% after five years. Meanwhile, in a separate study, the federal Centers for Disease Control and Prevention (CDC) arrived at similar numbers and reached similar conclusions.

The study authors said the issue may involve a new DTaP vaccine introduced in the early 1990s, which was then considered superior to its predecessor because it caused less side effects.

The authors point out that the current vaccine is the best protection for children against pertussis, but say that more research is needed to improve the shot, writing that, “our findings highlight the need to develop new pertussis-containing vaccines that will provide long-lasting immunity,” according to The LA Times.

We previously wrote that the sometimes-fatal bacterial respiratory infection was making a comeback, with the outbreak occurring in four states several years ago, despite mandatory vaccinations for children of school age.

We’ve also previously written that, pertussis, long considered a childhood illness, occurs in substantial numbers of cases in adolescents and adults whose immunity has diminished. A fairly recent vaccine called T/dap, a combined tetanus, diphtheria, and pertussis formulation, was designed for people between the ages of 19 and 64 for this purpose.

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