To assess the risk of pertussis by time since vaccination in children in Minnesota and Oregon who received 5 doses of acellular pertussis vaccines (DTaP).
These cohort analyses included Minnesota and Oregon children born between 1998 and 2003 who had 5 DTaP doses recorded in state Immunization Information Systems. Immunization records and statewide pertussis surveillance data were combined. Incidence rates and risk ratios for pertussis were calculated for the 6 years after receipt of the fifth DTaP dose.
The cohorts included 224 378 Minnesota children and 179 011 from Oregon; 458 and 89 pertussis cases were identified in Minnesota and Oregon, respectively. Pertussis incidence rates rose each year of follow-up: 15.6/100 000 (95% confidence interval [CI]: 11.1–21.4) at year 1 to 138.4/100 000 (CI: 113.3–166.9) at year 6 (Minnesota); 6.2/100 000 (CI: 3.3–10.6) in year 1 to 24.4/100 000 (CI: 15.0–37.8) in year 6 (Oregon). Risk ratios increased from 1.9 (CI: 1.3–2.9) in year 2 to 8.9 (CI: 6.0–13.0) in year 6 (Minnesota) and from 1.3 (CI: 0.6–2.8) in year 2 to 4.0 (CI: 1.9–8.4) in year 6 (Oregon).
This evaluation reports steady increase in risk of pertussis in the years after completion of the 5-dose DTaP series. This rise is likely attributable in part to waning immunity from DTaP vaccines. Continuing to monitor disease burden and vaccine effectiveness in fully vaccinated children in coming years will be important to assess ongoing risk as additional cohorts vaccinated solely with acellular pertussis vaccines are introduced.
Comments
Letter to Editor: Waning Immunity to Pertussis following 5 doses of DTaP
Waning Immunity to Pertussis following 5 doses of DTaP
Dear Editor , We read with interest the article by Sara Y Tartof et al on waning immunity to pertussis. It is a large scale cohort study with aim of finding out the rate at which the immunity against pertussis is decreasing. With respect to the current study, we have the following observation:
1. The authors have not described the population under study as to which community had higher incidence of pertussis, what were the living conditions of the population, whether there was any overcrowding or poor hygiene and sanitation facilities in their locality.
2. The authors have taken the data from other state agencies like IIS and National Notifiable Disease Surveillance System retrospectively and the authors themselves admit to the fact that the data regarding the vaccines was missing at places, which we feel, makes the study an underpowered study.
3. Were the laboratory kits used for diagnosis of pertussis standardized? ( whether supplied by same manufacturer all over the state)
4. The authors are attributing the increasing incidence of pertussis to waning immunity to DTaP vaccine. Well, demonstration of decreasing antibody levels would have contributed substantially to the study.
5. It seems that this study is propagating the requirement of a booster dose of aP vaccine. However in developing countries, where the risk of pertussis is higher and cases are more likely to be fatal, greater weight needs to be given to vaccine efficacy. If acellular vaccine has been shown to be less effective than a high-efficacy whole-cell vaccine, we would like to put forward a case for relook at the whole-cell vaccine rather than burdening the population with additional booster doses of acellular vaccine and thereby increasing the cost of administration of vaccines.
Conflict of Interest:
None declared