The epidemiology of invasive group a streptococcal infection and potential vaccine implications: United States, 2000-2004

Background. Invasive group A Streptococcus ( GAS) infection causes significant morbidity and mortality in the United States. We report the current epidemiologic characteristics of invasive GAS infections and estimate the potential impact of a multivalent GAS vaccine. Methods. From January 2000 through December 2004, we collected data from Centers for Disease Control and Prevention's Active Bacterial Core surveillance (ABCs), a population-based system operating at 10 US sites ( 2004 population, 29.7 million). We defined a case of invasive GAS disease as isolation of GAS from a normally sterile site or from a wound specimen obtained from a patient with necrotizing fasciitis or streptococcal toxic shock syndrome in a surveillance area resident. All available isolates were emm typed. We used US census data to calculate rates and to make age- and race-adjusted national projections. Results. We identified 5400 cases of invasive GAS infection (3.5 cases per 100,000 persons), with 735 deaths ( case-fatality rate, 13.7%). Case-fatality rates for streptococcal toxic shock syndrome and necrotizing fasciitis were 36% and 24%, respectively. Incidences were highest among elderly persons (9.4 cases per 100,000 persons), infants (5.3 cases per 100,000 persons), and black persons (4.7 cases per 100,000 persons) and were stable over time. We estimate that 8950-11,500 cases of invasive GAS infection occur in the United States annually, resulting in 1050 1850 deaths. The emm types in a proposed 26-valent vaccine accounted for 79% of all cases and deaths. Independent factors associated with death include increasing age; having streptococcal toxic shock syndrome, meningitis, necrotizing fasciitis, pneumonia, or bacteremia; and having emm types 1, 3, or 12. Conclusions. GAS remains an important cause of severe disease in the United States. The introduction of a vaccine could significantly reduce morbidity and mortality due to these infections.