Table 2.

Incidence of Severe and Nonsevere Pertussis, Overall and by Centers for Disease Control and Prevention Diagnostic Case Criteria

Category	No. of Infants	Person-time, mo	Incidence Rate per 1000 Person-months (95% CI)	Incidence per 1000 Infants (95% CI)
All positive Bordetella pertussis PCR assaysa
All pertussis	8	6654.5	1.14 (.57–2.28)	3.96 (1.84–7.50)
Nonsevere pertussis	5	6654.5	0.75 (.31–1.81)	2.47 (.90–5.48)
Severe pertussis	3	6654.5	0.43 (.14–1.33)	1.48 (.38–4.03)
Infants meeting CDC confirmed pertussis diagnostic criteria
All pertussis	5	6654.5	0.75 (.31–1.81)	2.47 (.90–5.48)
Nonsevere pertussis	2	6654.5	0.29 (.07–1.14)	0.99 (.17–3.27)
Severe pertussis	3	6654.5	0.43 (.14–1.33)	1.48 (.38–4.03)
Infants meeting CDC probable pertussis diagnostic criteria
All pertussis	2	6654.5	0.29 (.07–1.14)	0.99 (.17–3.27)
Nonsevere pertussis	2	6654.5	0.29 (.07–1.14)	0.99 (.17–3.27)
Severe pertussis	0	6654.5	0.0 (NA)	0.0 (NA)

Abbreviations: CDC, Centers for Disease Control and Prevention; CI, confidence interval; NA, not applicable; PCR, polymerase chain reaction.

^a Any infant meeting the syndromic screening definition with a positive PCR test.