Haemophilus Influenzae Type b Vaccine Shortage and Surveillance for Invasive Haemophilus Influenzae Disease — United States, 2007-2008

Background:
The prolonged shortage and ongoing deferral of Haemophilus influenzae type b (Hib) vaccine booster dose may put the United States at risk of a resurgence of Hib disease in children <5 years. Surveillance for H. influenzae (H flu) disease is crucial for identifying and responding to any increases in Hib incidence, and serotyping of H flu isolates is critical for distinguishing Hib disease from disease due to non-b H flu.

Objectives:
To evaluate completeness of serotype information in cases of H flu reported to CDC among children <5 in the US.

Methods:
We merged H flu cases (defined as isolation of H flu from a normally sterile site) reported from January 2007 to October 2008 through the National Notifiable Diseases Surveillance System (NNDSS) and the Active Bacterial Core surveillance system (ABCs). We evaluated the completeness of serotype data for reported cases in children <5 years.

Results:
We identified 748 H flu cases among children <5 years; 48 (6.0%) were serotype b and 278 (37.2%) were missing serotype information. Among the 49 jurisdictions reporting H flu cases in children <5 years, 19 (39%) were missing serotype data on more than 50% of cases and 7 (14%) were missing serotype data for all reported cases. Among the five jurisdictions fully covered by ABCs surveillance, the median proportion of cases with missing serotype data was 0%; among the 42 jurisdictions not participating in ABCs the median was 50.0%.

Conclusions:
A similar evaluation in 2006 found NNDSS data were missing serotype information for 48% of H flu case reports. Serotype reporting has improved somewhat since then. However, serotype was still missing in 37% of 2007-2008 cases. Hib surveillance requires timely investigation and reporting of all H flu cases, and increased efforts to serotype all cases of H flu in children <5 years.