June 2010 California Pertussis Update

Pertussis Background

• Pertussis is the most poorly controlled vaccine-preventable disease Incidence increasing since the 1990s Cyclical: peaks every 2-5 years as numbers of

susceptible people increase enough to allow sustained transmission; last peak year 2005 with 25,616 U.S. cases, a 45 year high

• Adults are vulnerable to pertussis 27% of reported cases are among adults Pertussis immunity wanes 5 to 10 years after DTaP*

series (immunity from disease wanes in 15 years) ~25% of cough illness lasting >2 weeks is pertussis

• First pertussis vaccines (Tdap)† for adolescents and adults licensed in 2005; uptake suboptimal

*Diphtheria and tetanus toxoids and acellular pertussis vaccine†Tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine

Typical Symptoms of Pertussis

• Three-stage bacterial illness (catarrhal, paroxysmal and convalescent) that lasts 4-12 weeks

• Typical symptoms paroxysmal cough lack of fever no systemic illness coryza; no pharyngitis posttussive vomiting posttussive whoop absolute lymphocytosis

• Adults with pertussis often report feeling as if they’re choking on something, sweating episodes

Pertussis in Young Infants

• Initially infant looks deceptively well; coryza, no fever, mild cough

• Leukocytosis with lymphocytosis• Apneic episodes• Seizures• Respiratory distress• Pneumonia• Adenovirus or RSV coinfection can confuse

picture

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

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Pertussis resurgence since the 1990s

• Genetic changes in B. pertussis; greater virulence?

• Variable vaccine efficacy (acellular pertussis vaccines licensed in 1991 for 4th/5th doses; entire series in 1996)

• Waning of vaccine-induced immunity and lack of natural booster events

• General availability of better laboratory tests• Greater awareness of pertussis by clinicians

Number of reported pertussis cases by onset year ― California,

1913-2009

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5,000

10,000

15,000

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25,000

1913 1923 1933 1943 1953 1963 1973 1983 1993 2003

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Number of reported pertussis cases, by year, California, 1976-2009

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Hospitalized Pertussis cases by age – California, 1998-2009

Number of pertussis cases, hospitalizations and deaths, by onset year

– California, 2003-2009

§2009 data provisional

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Deaths

California Pertussis Cases - 2010• As of 6/15/2010, there have been 910 pertussis

cases reported in 2010, a 4-fold increase from the number of reported cases during the same time period in 2009; an additional 600 cases are under investigation

• From January through June of 2005 there were 1,261 pertussis cases; these data suggest the disease burden is at or above the levels seen in 2005, which was a 45 year high in cases

• Other states are reporting 2010 increases to CDC, but none reporting increases similar to those in California

• Possible differences in states with and without middle school Tdap vaccination requirement

Children's Hospital Central CaliforniaLaboratory Confirmed Cases of Pertussis (6/17/10)

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19

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-07

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-07

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Dec

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-08

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r-08

May

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Month of Diagnosis

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2010

X=2009 death (symptom onset)X=2010 death (symptom onset)

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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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California Pertussis Deaths• Five deaths in 2010 to date• All CA pertussis deaths (~3/year) since 1996,

except one, have been in infants <3 months of age; age at symptom onset ranged from 5 days – 8 weeks

• 80% Hispanic (50% of birth cohort Hispanic)• The mean WBC of fatal cases in 1998-2009 was

75,000 (range 15,000-148,000) Pertussis toxin elicits a dose-dependent leukocytosis

• Of those with known status, all had pulmonary HTN Increases in leukocyte mass can diminish blood flow by

increasing vascular resistance; however, pulmonary HTN is generally initiated and maintained by many factors

• Risk factor study being conducted

Age-specific pertussis rates by race/ethnicity -- California, 2010

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<1 1-6 7-9 10-18 19-64 65+

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White

Hispanic

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Black

2008 Infant Pertussis Hospitalization Costs in California• In 2008, there were 222 hospitalizations in infants

<1 year of age with the diagnosis code for pertussis 96% were <4 months of age at admission Median length of stay 3.5 days (range 1—52 days) 2 deaths 73% Medi-Cal payer 63% Hispanic 22% White 5% Black 3% API

• Charge data is listed for 202 hospitalizations, of these: Mean total charge: $46,328 Median total charge: $18,966 Range $2,876--$798,748

Pertussis Mitigation• Promote the use of Tdap - particularly in those

who have contact with infants Free vaccine through 9/30/2010 for birth hospitals with

postpartum Tdap policies; encourage ED use of Tdap Work with payers re: Tdap reimbursement

• Clinician education CDPH Tdap recommendations Pertussis signs and symptoms Treatment recommendations for infants with severe

pertussis Accelerated DTaP schedule for infants

• Public education Vaccination/cocooning Pertussis signs and symptoms Keep ill people away from infants

Pertussis Transmission to Infants• Adults transmit pertussis to infants

Among 264 known source-cases:Almost 50% were parents, most often mothers51% were adults >19 years of age

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.

Pertussis incidence by age -- California, 2010

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<1 1-6 7-9 10-18 19-64 65+

age group

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Cases and incidence of laboratory confirmed pertussis cases by age –

California, 2008

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All ages

Pertussis incidence by age group (excluding infants)-- California, 2005-2010

Pertussis incidence by age group (excluding infants) – U.S. 2004-2008