Effectiveness of Postpartum Tdap

Immunization in California Hospitals

K. Winter, K. Harriman, R. Schechter, J. Chang, J. Talarico

California Department of Public Health

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

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

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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.

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

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

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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?

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

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

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

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)

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

2006 2009

Hospitals with Tdap policy (n=48) 46.8 (34.1-59.5) 23.8 (14.7-33.0)

Hospitals with no Tdap policy (n=145) 29.7 (23.7-35.8) 35.7 (29.0-42.3)

Overall pertussis incidence in infants <4 months of age statewide and in facilities with and without a postpartum

Tdap policy – California, 2006-2009

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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.

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

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