Is it time to revise the schedule for pertussis vaccination?

June 14, 2012

Findings of a new study suggest that the current schedule of acellular pertussis vaccination is not sufficient to prevent outbreaks of the disease. The rate of vaccine failure rose as the interval from the last dose increased. Should earlier or more frequent booster doses be recommended?

Findings of a new study suggest that the current schedule of acellular pertussis vaccination is not sufficient to prevent outbreaks of the disease.

Although widespread vaccination of children has greatly reduced the incidence of pertussis, the disease remains prevalent, with outbreaks peaking every 2 to 5 years. Currently, the acellular pertussis vaccine is given at 2, 4, 6, and 15 to 18 months and 4 to 6 years, with a booster at 10 to 12 years.

Recent data suggest that the vaccine is not as effective as previously believed, and its long-term durability has not been determined. After a large pertussis outbreak in California in 2010, researchers at Kaiser Permanente Medical Center examined the incidence of pertussis and the effectiveness of the acellular pertussis vaccine in a well-vaccinated, well-defined population.

Of 171 cases of clinical pertussis identified, 132 were in pediatric patients; 81% were fully vaccinated, 11% were undervaccinated, and 8% were never vaccinated. The highest incidence of disease was in children aged 8 to 12 years, which corresponded with the interval since the last scheduled vaccine at 4 to 6 years. The vaccine was 41% effective in protecting children aged 2 to 7 years but only 24% effective for children aged 8 to 12 years. In teens aged 13 to 18 years, the vaccine was 79% effective.

The findings indicate that the durability of the acellular pertussis vaccine is limited and that susceptibility to infection increases as the interval from the last doses increases. The current recommendation for booster shots at 10 to 12 years of age may be too late to provide protection for this age group, the researchers suggest. Earlier or more numerous booster doses either as part of routine immunization or for outbreak control should be considered.

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