Effectiveness of Postpartum Tdap Immunization in California Hospitals

1. Effectiveness of Postpartum Tdap Immunization in California Hospitals K. Winter, K. Harriman, R. Schechter, J. Chang, J. TalaricoCalifornia Department of Public Health

2. Background – Pertussis in infants • Pertussis is an acute and prolonged cough illness caused by Bordetella pertussis • Most severe disease occurs in infants <3 months of age • >60% of infected infants <1 year are hospitalized • All pertussis deaths in CA since 1998 have been in infants <3 months of age (n=43) • Infants do not start DTaP series until 2 months of age and are not fully protected until 18 months

3. Pertussis hospitalizations in infants <1 year, by age in weeks –California, 2008

4. Background – Postpartum Tdap • Source of pertussis infection in infants has been linked to parents, most often mothers, in 20%-55% of cases* • First pertussis vaccine for adolescents and adults licensed in 2005 (Tdap) • Advisory Committee for Immunization Practices recommended vaccination of close contacts of infants as part of ‘cocooning’ strategy in 2006 *Bisgard KM, et al. Infant pertussis: who was the source? Pediatr Infect Dis J 2004; 23(11):985-989. Wendelboe AM, et al. Transmission of Bordetella pertussis to young infants. Pediatr Infect Dis J 2007; 26(4):293-299.

5. Background – Pertussis on the rise • Pertussis is cyclical with peaks occurring every 3-5 years. • Last peak occurred in 2005 when >3,000 cases were reported and 8 infants died in California • Data suggests that 2010 will be another peak year in California • 3 times as many cases were reported from January 1-May 31, 2010 as the same period in 2009 • 5 infants have died, all <3 months of age • This year we have an intervention: Tdap

6. Epidemic curve of pertussis cases by month of report and deaths by month of onset– California, 2009-2010 X X 2009 death X 2010 death X X X X X X X

7. Study Questions • Is postpartum Tdap vaccination an effective strategy to reduce transmission of B. pertussis to young infants? • How many birthing facilities in California have policies to administer Tdap vaccine to postpartum women?

8. Methods • Distributed survey to Infection Preventionists and Labor and Delivery Managers at California hospitals with >50 births/year (n=267) • Does facility have a postpartum Tdap policy? • When (month/year) was it implemented? • Also obtained a brief description of the policy and description of any barriers to implementation • Attempted to identify birth hospital for all reported pertussis cases <4 months of age born 2006-2009 in California • For cases born 2006-2008: Matched pertussis cases to birth record (vital statistics) using name and DOB to identify birth hospital • For cases born 2009: Birth hospital reported on case report form

9. Methods, continued • Calculated annual rate of pertussis among infants born in each facility (# cases/total births) • Compared pertussis incidence before and after Tdap policy implementation • If month of implementation was unknown, assumed to be January • Evaluated incidence over time in all hospitals

10. Results • 744 infants <4 months of age were infected with pertussis • 537 (72%) hospitalized • 10 (1%) died • Hospital of birth identified in 620 (83%) • 214 of 267 (80%) facilities with >50 births responded to survey • 53 (25%) implemented a postpartum Tdap policy by the end of 2009 • First Tdap policy was implemented in January 2007 • 161 (controls) had no policy or were in process of implementation

11. Results, continued • Pertussis incidence after postpartum Tdap policy implementation: • Declined or remained at 0 in 42 (79%) facilities • Increased in 11 (21%) facilities • Overall incidence in all facilities with a Tdap policy declined significantly after policy implementation • Before Tdap policy: 41.7 cases/100,000 births (95% CI 34.4-49.0) • After Tdap policy: 19.2 cases/100,000 births (95% CI 12.7-25.6)

12. Results, continued • Pertussis incidence over time also declined significantly in hospitals with a postpartum Tdap vaccination policy from 2006 (when no postpartum Tdap policies existed) to 2009 (when 53 policies existed) • Increase in incidence was observed in control hospitals

13. Overall pertussis incidence in infants <4 months of age statewide and in facilities with and without a postpartum Tdap policy – California, 2006-2009

14. Conclusions • Decline in pertussis incidence observed in facilities with a postpartum Tdap vaccination policy suggests that vaccinating new mothers may reduce transmission to infants. • Although recommended in 2006, only ¼ of birthing hospitals had implemented a postpartum Tdap policy by 2009. Additional efforts are needed to encourage facilities to adopt cocooning policies.

15. Data limitations • Pertussis incidence for infants born late in 2009 incomplete (onset in 2010) • Vaccine uptake in facilities with a Tdap policy was unknown • Maternal vaccination status for infant cases unknown

16. Recommendations • To increase postpartum Tdap uptake, CDPH is now recommending no minimum interval between Td and Tdap • CDPH also providing a limited quantity of free Tdap vaccine to birthing facilities to help establish cocooning programs • Include hospital of birth on case report form for infants <1 year of age • Identify hospitals with highest rates of pertussis and encourage to adopt postpartum Tdap policies