Monday, May 20, 2013

Pertussis: Effectiveness Of Whole Cell vs Acellular Vaccine in Teenagers


Credit CDC Pink Book


# 7293


The dramatic drop in Pertussis (aka Whooping Cough) - as shown in the chart above  - began in the early 1940s following the introduction of the first whole-cell pertussis vaccine (combined with diphtheria and tetanus toxoids).


Before the vaccine was available, more than 160,000 cases  (and about 5,000 deaths) were recorded annually across the nation, but by 1976 the number of reported cases reached a record-low of 1,010 cases, a decrease of 99%


But over the past decade the number of cases has steadily risen, and in 2012 more than 40,000 cases were reported in the United States.


Similar increases have been reported in the UK (see UK: Whooping Cough Numbers Decline After Record Year), and Australia


The reasons behind these increases are complex, and not completely understood, but some factors are believed to be:

  • lower vaccination uptakes
  • the move away from whole cell pertussis vaccines to safer acellular vaccines in the 1990s
  • evolutionary changes in the Bordetella pertussis bacteria.


In 2010 California was hit particularly hard by a sudden resurgence in Pertussis cases, which resulted in more than 9,000 cases, the most in over 60 years, including 10 infant deaths. The following chart shows California’s dramatic upswing in Pertussis since the 1980s.



Last year, we began to see more studies suggesting that the newer acellular pertussis vaccine – introduced in the 1990s for safety reasons – might not be as protective as the older vaccine (see JAMA: Waning Pertussis Vaccine Effectiveness Over Time).


Today, we’ve another study, this time from Kaiser Permanente in California, that looked at children (ages 10-17) born between 1994 and 1999, and how they fared during the 2010 outbreak. 


Some of these children only received the older whole cell vaccine – while some had a combination of the older and newer vaccine – and some only received the newer acellular vaccine.


The results are outlined in a press release this morning.


Kaiser Permanente

Whole-cell vaccine was more effective than acellular vaccine during CA pertussis outbreak

OAKLAND, Calif., May 20, 2013 — Whole-cell pertussis vaccines were more effective at protecting against pertussis than acellular pertussis vaccines during a large recent outbreak, according to a new Kaiser Permanente study published in Pediatrics.


Teenagers who were vaccinated with four doses of acellular vaccines were at almost six times higher risk of pertussis than were those who had received four doses of whole-cell vaccines. Persons who received mixed whole-cell and acellular vaccines had an intermediate level of risk between those who received all whole-cell or all acellular vaccines. Those who received mixed vaccines were at nearly four times higher risk of pertussis than were those who received all whole-cell vaccines.

(Continue . . . )


The full study appears in Pediatrics.

Comparative Effectiveness of Acellular Versus Whole-Cell Pertussis Vaccines in Teenagers

  • Nicola P. Klein,
  • Joan Bartlett,
  • Bruce Fireman,
  • Ali Rowhani-Rahbar,
  • and Roger Baxter
Pediatrics peds.2012-3836; Published online May 20, 2013 (10.1542/peds.2012-3836)


While the newer acellular vaccine appears to be protective in the short run, over time its effectiveness appears to drop dramatically.


Complicating matters further, earlier this year researchers at St. Christopher’s Hospital for Children in Philadelphia, PA reported that  11 of 12 isolates of B. Pertussis they examined in 2011-2012 using Western blot analysis failed to detect Pertactin (see NEJM: Pertactin Resistant Bordetella Pertussis – United States).


Pertactin (PRN) is a membrane protein that facilitates the attachment of Bordetella pertussis bacteria to epithelial cells in the trachea, and is one of the prime components of the acellular pertussis vaccine introduced in the 1990s.


The researchers state, "To our knowledge, this finding represents the first reported occurrence of pertactin-negative variants of B. pertussis in the U.S.”

Similar pertactin-negative strains have been reported in Japan, France, and Finland. Pertactin-negative strains reportedly remain infectious in humans, and retain lethality in laboratory testing on mice.


While the long-term solution to this problem will have to await the development of newer, longer-lasting, and more broadly protective pertussis vaccines, for now following the CDC’s  Pertussis Vaccination Guidelines remains your best strategy to protect yourself and your family.


And for more on Pertussis, visit the CDC’s Pertussis page.