JAMA   
November 28, 2012, Vol 308, No. 20
http://jama.ama-assn.org/current.dtl

Original Contribution
Association of Childhood Pertussis With Receipt of 5 Doses of Pertussis Vaccine by Time Since Last Vaccine Dose, California, 2010
Lara K. Misegades, PhD, MS; Kathleen Winter, MPH; Kathleen Harriman, PhD, MPH, RN; John Talarico, DO, MPH; Nancy E. Messonnier, MD; Thomas A. Clark, MD, MPH; Stacey W. Martin, MSc
JAMA. 2012;308(20):2126-2132. doi:10.1001/jama.2012.14939.

ABSTRACT
Context  In 2010, California experienced its largest pertussis epidemic in more than 60 years; a substantial burden of disease was noted in the 7- to 10-year-old age group despite high diphtheria, tetanus, and acellular pertussis vaccine (DTaP) coverage, indicating the possibility of waning protection.

Objective  To evaluate the association between pertussis and receipt of 5 DTaP doses by time since fifth DTaP dose.

Design, Setting, and Participants  Case-control evaluation conducted in 15 California counties. Cases (n = 682) were all suspected, probable, and confirmed pertussis cases among children aged 4 to 10 years reported from January through December 14, 2010; controls (n = 2016) were children in the same age group who received care from the clinicians reporting the cases. Three controls were selected per case. Vaccination histories were obtained from medical records and immunization registries.

Main Outcome Measures  Primary outcomes were (1) odds ratios (ORs) for the association between pertussis and receipt of the 5-dose DTaP series and (2) ORs for the association between pertussis and time since completion (<12, 12-23, 24-35, 36-47, 48-59, or ≥60 months) of the 5-dose DTaP series. Logistic regression was used to calculate ORs, accounting for clustering by county and clinician, and vaccine effectiveness (VE) was estimated as (1 − OR) × 100%.

Results  Among cases and controls, 53 (7.8%) and 19 (0.9%) had not received any pertussis-containing vaccines, respectively. Compared with controls, children with pertussis had a lower odds of having received all 5 doses of DTaP (OR, 0.11; 95% CI, 0.06-0.21 [estimated VE, 88.7%; 95% CI, 79.4%-93.8%]). When children were categorized by time since completion of the DTaP series, using an unvaccinated reference group, children with pertussis compared with controls were less likely to have received their fifth dose within the prior 12 months (19 [2.8%] vs 354 [17.6%], respectively; OR, 0.02; 95% CI, 0.01-0.04 [estimated VE, 98.1%; 95% CI, 96.1%-99.1%]). This association was evident with longer time since vaccination, with ORs increasing with time since the fifth dose. At 60 months or longer (n = 231 cases [33.9%] and n = 288 controls [14.3%]), the OR was 0.29 (95% CI, 0.15-0.54 [estimated VE, 71.2%; 95% CI, 45.8%-84.8%]). Accordingly, the estimated VE declined each year after receipt of the fifth dose of DTaP.

Conclusion  Among children in 15 California counties, children with pertussis, compared with controls, had lower odds of having received the 5-dose DTaP series; as time since last DTaP dose increased, the odds increased, which is consistent with a progressive decrease in estimated vaccine effectiveness each year after the final dose of pertussis vaccine.

Pertussis remains a poorly controlled vaccine-preventable disease in the United States, despite a well-established childhood vaccination program and high coverage.1 Although infants have substantially higher rates of pertussis compared with other age groups, data from the National Notifiable Diseases Surveillance System reflect a recent increase in the number of reported pertussis cases among children aged 7 to 10 years. In 2010, this age group had the second highest incidence of pertussis in the United States.2 The changing epidemiology raises important questions about possible waning protection from the childhood acellular pertussis vaccine series.

After the diphtheria, tetanus, and whole-cell pertussis (DTwP) vaccine was introduced in the late 1940s, a dramatic decline occurred in the number of reported pertussis cases. However, whole-cell vaccine was commonly associated with local adverse events (eg, redness, swelling, and pain at the injection site) and less commonly with more serious adverse events.3– 4 These safety concerns prompted development and licensure of diphtheria, tetanus, and acellular pertussis (DTaP) vaccines, which were recommended by the Advisory Committee on Immunization Practices in 1992 for childhood booster doses at 15 to 18 months and 4 to 6 years of age and in 1997 for the complete 5-dose series, including the primary doses at 2, 4, and 6 months of age.5 In 2006, an adolescent booster dose (Tdap) was recommended at age 11 to 12 years.6 Recent studies have demonstrated waning protection following the current 5-dose DTaP schedule, but no study, to our knowledge, has compared fully vaccinated with unvaccinated children to estimate the durability of protection afforded by the childhood series.7– 8

In 2010, California experienced its largest pertussis epidemic in more than 60 years; more than 9000 pertussis cases were reported and 10 infants died.9 Concordant with national trends, a substantial burden of disease (67.9 cases per 100 000) occurred in 7- to 10-year-olds despite high DTaP coverage.2 Concern about the number of cases in California and the increasing burden of pertussis among 7-to 10-year-olds prompted a large-scale assessment of the long-standing pertussis childhood vaccination program. The objectives of the investigation were to evaluate the association between pertussis and receipt of 5 DTaP doses by time since the fifth DTaP dose.

Editorial
Acellular Vaccines and Resurgence of Pertussis
Eugene D. Shapiro, MD
JAMA. 2012;308(20):2149-2150. doi:10.1001/jama.2012.65031.

Extract
Pertussis is a highly contagious, vaccine-preventable disease for which a whole-cell vaccine (killed bacteria), in combination with toxoids against diphtheria and tetanus (DTwP), was introduced for immunization of children in the United States in the 1940s. With the eventual widespread use of DTwP vaccine, the national annual incidence of reported cases of pertussis decreased at least 150- to 200-fold, with only 1010 reported cases in 1976.1 Because of high rates of both local and systemic adverse events associated with DTwP vaccine, acellular pertussis vaccines (DTaP) that contain a small number of purified antigens of Bordetella pertussis and have far fewer adverse effects replaced DTwP vaccine in the 1990s. The DTaP vaccine is currently recommended for both primary (3 doses administered at 2, 4, and 6 months of age) and booster (2 doses administered at 15 to 18 months and 4 to 6 years of age) immunizations.2 In 2005, formulations suitable for adolescents and adults (Tdap vaccine) were approved, and an additional 1-time booster dose is recommended…