Pertussis Immunity Lasts Only Few Years After DTaP Immunization

By Will Boggs MD

January 06, 2015

NEW YORK (Reuters Health) - The average duration of protection against pertussis after diphtheria-tetanus-acellular pertussis (DTaP) immunization is only about three years, according to a review and meta-analysis of a dozen studies.

"There was suspicion in the vaccine community that duration of protective immunity for DTaP was shorter than originally anticipated, but this meta-analysis demonstrates just how short that might be," Ashleigh McGirr from the University of Toronto in Canada told Reuters Health by email.

Several reports have suggested that waning immunity of vaccinated individuals may contribute to the recent resurgence of pertussis in several countries.

McGirr and Dr. David N. Fisman undertook a review and meta-analysis to estimate the duration of protective immunity to pertussis after three and five doses of DTaP. They identified six five-dose studies and six three-dose studies conducted in the U.S., Germany, Italy, Sweden, and Senegal.

The final regression model showed that each year since the last dose of DTaP increased the odds of pertussis by 33%, with no meaningful differences between the three- and five-dose regimens.

Based on this model, the average duration of vaccine protection from DTaP, assuming 85% vaccine efficacy, would be about three years, and only 10% of children vaccinated with DTaP would remain protected 8.5 years after their last dose, according to the January 5 Pediatrics online report.

"Providers and policy makers may consider immunizing adolescents at an earlier age," McGirr said. "Similarly, repeat booster immunizations may be necessary to achieve herd immunity and prevent the transmission of pertussis."

"Physicians should be aware that duration of protective immunity to DTaP may not be as long as originally thought," she concluded. "They may need to counsel patients on the appropriateness of adolescent and adult boosters."

Dr. Nicole Guiso, from the Pasteur Institute in Paris, France, told Reuters Health by email, "Subunit vaccines are not inducing a long time immunity. It was well known; furthermore, the duration of immunity after infection is also short . . . it is difficult to do better than nature. Remember that you can have the disease two to three times in your life."

"First of all, we need to increase herd immunity and to obtain over 90% vaccine coverage for primary and first boosters," she said. "Afterward we need, as for diphtheria, to introduce a booster for adolescents and for adults. Not necessarily every 10 years. If the herd immunity is high enough the interval between vaccinations can be increased."

"(It is) important to follow recommendations and maintain a very high vaccine coverage," Dr. Guiso concluded.

SOURCE: http://bit.ly/14qiJM3

Pediatrics 2015

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