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Pertussis prevention strategies should be reevaluated
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CHICAGO — Recent pertussis outbreaks in the US have highlighted the need for increased focus on prevention and immunization, according to a speaker here at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy.
C. Mary Healy, MD, assistant professor at Baylor College of Medicine in Houston, said that pertussis was a vaccine success story after introduction in the 1950s. She noted that the infection is now reduced by about 95%.
“However, immunity wanes over 5 to 10 years,” she said. “This is an infection with high attack rates, and one that often goes unrecognized. The result has been a slow but inexorable increase in pertussis since 1976.”
The increase was punctuated by the outbreak in California in 2010, which had the highest number of reported cases since 1947, and had an attack rate of 23.4 per 100,000, according to Healy. She also highlighted smaller outbreaks in Michigan and Ohio in 2010 that did not receive as much attention.
“Improved detection methods may be driving the current resurgence, but it may be overly simplistic to attribute it just to that cause,” she said. She suggested that variations in Bordetella pertussis may also be contributing.
California responded by expanding and accelerating immunization programs for tetanus-diphtheria-acellular pertussis (Tdap) and diphtheria-tetanus toxoids and acellular pertussis vaccine (DTaP), and facilitating reimbursement for those immunizations. However, this may not be enough, according to Healy.
“As we all know, those who are most vulnerable are those who are too young to have finished the primary immunization series,” she said. “Those infants also have highest complication rate.”
Healy also noted that Hispanics are at a particularly high risk for the infection, which she suggested may be due to increased family contact in that community. This point highlights the fact that infants are infected with pertussis by the mother in 33% of cases, by the father in 16% and by a sibling in 19%.
Healy discussed three immunization strategies to reduce pertussis incidence: neonatal, maternal and cocooning.
She suggested that all present the usual challenges, including resistance to the practice of immunization, safety and difficulty in implementation.
“Neonatal immunization with the monovalent acellular pertussis vaccine should be investigated,” she said. “As for maternal immunization, safety is a big consideration, as is timing to gain the optimal antibody transfer.”
Cocooning presents the most difficulties because all infant caregivers should be targeted, according to Healy. “Post-partum women, fathers, contacts of infants and health care providers all need to be immunized in this strategy,” Healy said. “If it takes a village to raise a child, you better make sure the village is vaccinated.”
Healy concluded that maternal immunization is the most promising strategy overall, but that cocooning, while necessary, presents the biggest challenges.
For more information:
- Healy MC. #1077. Impact of Pertussis Outbreaks and Prospects for Prevention. Presented at: 51st ICAAC. Sept. 17-20, 2011. Chicago.
Disclosure: Dr. Healy reports receiving grants from Sanofi Aventis and Novartis and being on the advisory board of Novartis.
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