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.