Current Epidemiology and Trends in Invasive Haemophilus influenzae Disease-United States, 2009-2015.

Background: Following Haemophilus influenzae serotype b (Hib) conjugate vaccine introduction in the 1980s, Hib disease in young children dramatically decreased, and epidemiology of invasive H. influenzae changed. Methods: Active surveillance for invasive H. influenzae disease was conducted through Active Bacterial Core surveillance sites. Incidence rates were directly standardized to the age and race distribution of the US population. Results: During 2009-2015, the estimated mean annual incidence of invasive H. influenzae disease was 1.70 cases per 100000 population. Incidence was highest among adults aged ≥65 years (6.30) and children aged <1 year (8.45); many cases in infants aged <1 year occurred during the first month of life in preterm or low-birth-weight infants. Among children aged <5 years (incidence: 2.84), incidence was substantially higher in American Indian and Alaska Natives AI/AN (15.19) than in all other races (2.62). Overall, 14.5% of cases were fatal; case fatality was highest among adults aged ≥65 years (20%). Nontypeable H. influenzae had the highest incidence (1.22) and case fatality (16%), as compared with Hib (0.03; 4%) and non-b encapsulated serotypes (0.45; 11%). Compared with 2002-2008, the estimated incidence of invasive H. influenzae disease increased by 16%, driven by increases in disease caused by serotype a and nontypeable strains. Conclusions: Invasive H. influenzae disease has increased, particularly due to nontypeable strains and serotype a. A considerable burden of invasive H. influenzae disease affects the oldest and youngest age groups, particularly AI/AN children. These data can inform prevention strategies, including vaccine development.

Generalisability of vaccine effectiveness estimates: an analysis of cases included in a postlicensure evaluation of 13-valent pneumococcal conjugate vaccine in the USA.

OBJECTIVES: External validity, or generalisability, is the measure of how well results from a study pertain to individuals in the target population. We assessed generalisability, with respect to socioeconomic status, of estimates from a matched case-control study of 13-valent pneumococcal conjugate vaccine effectiveness for the prevention of invasive pneumococcal disease in children in the USA. DESIGN: Matched case-control study. SETTING: Thirteen active surveillance sites for invasive pneumococcal disease in the USA. PARTICIPANTS: Cases were identified from active surveillance and controls were age and zip code matched. OUTCOME MEASURES: Socioeconomic status was assessed at the individual level via parent interview (for enrolled individuals only) and birth certificate data (for both enrolled and unenrolled individuals) and at the neighbourhood level by geocoding to the census tract (for both enrolled and unenrolled individuals). Prediction models were used to determine if socioeconomic status was associated with enrolment. RESULTS: We enrolled 54.6% of 1211 eligible cases and found a trend toward enrolled cases being more affluent than unenrolled cases. Enrolled cases were slightly more likely to have private insurance at birth (p=0.08) and have mothers with at least some college education (p<0.01). Enrolled cases also tended to come from more affluent census tracts. Despite these differences, our best predictive model for enrolment yielded a concordance statistic of only 0.703, indicating mediocre predictive value. Variables retained in the final model were assessed for effect measure modification, and none were found to be significant modifiers of vaccine effectiveness. CONCLUSIONS: We conclude that although enrolled cases are somewhat more affluent than unenrolled cases, our estimates are externally valid with respect to socioeconomic status. Our analysis provides evidence that this study design can yield valid estimates and the assessing generalisability of observational data is feasible, even when unenrolled individuals cannot be contacted.

On-site availability of Legionella testing in acute care hospitals, United States.

We surveyed 399 US acute care hospitals regarding availability of on-site Legionella testing; 300 (75.2%) did not offer Legionella testing on site. Availability varied according to hospital size and geographic location. On-site access to testing may improve detection of Legionnaires disease and inform patient management and prevention efforts.

National burden of invasive methicillin-resistant Staphylococcus aureus infections, United States, 2011.

IMPORTANCE: Estimating the US burden of methicillin-resistant Staphylococcus aureus (MRSA) infections is important for planning and tracking success of prevention strategies. OBJECTIVE: To describe updated national estimates and characteristics of health care- and community-associated invasive methicillin-resistant Staphylococcus aureus (MRSA) infections in 2011. DESIGN, SETTING, AND PARTICIPANTS: Active laboratory-based case finding identified MRSA cultures in 9 US metropolitan areas from 2005 through 2011. Invasive infections (MRSA cultured from normally sterile body sites) were classified as health care-associated community-onset (HACO) infections (cultured ≤ 3 days after admission and/or prior year dialysis, hospitalization, surgery, long-term care residence, or central vascular catheter presence ≤ 2 days before culture); hospital-onset infections (cultured >3 days after admission); or community-associated infections if no other criteria were met. National estimates were adjusted using US census and US Renal Data System data. MAIN OUTCOMES AND MEASURES: National estimates of invasive HACO, hospital-onset, and community-associated MRSA infections using US census and US Renal Data System data as the denominator. RESULTS: An estimated 80,461 (95% CI, 69,515-93,914) invasive MRSA infections occurred nationally in 2011. Of these, 48,353 (95% CI, 40,195-58,642) were HACO infections; 14,156 (95% CI, 10,096-20,440) were hospital-onset infections; and 16,560 (95% CI, 12,806-21,811) were community-associated infections. Since 2005, adjusted national estimated incidence rates decreased among HACO infections by 27.7% and hospital-onset infections decreased by 54.2%; community-associated infections decreased by only 5.0%. Among recently hospitalized community-onset (nondialysis) infections, 64% occurred 3 months or less after discharge, and 32% of these were admitted from long-term care facilities. CONCLUSIONS AND RELEVANCE: An estimated 30,800 fewer invasive MRSA infections occurred in the United States in 2011 compared with 2005; in 2011 fewer infections occurred among patients during hospitalization than among persons in the community without recent health care exposures. Effective strategies for preventing infections outside acute care settings will have the greatest impact on further reducing invasive MRSA infections nationally.

An assessment of the screening method to evaluate vaccine effectiveness: the case of 7-valent pneumococcal conjugate vaccine in the United States.

The screening method, which employs readily available data, is an inexpensive and quick means of estimating vaccine effectiveness (VE). We compared estimates of effectiveness of heptavalent pneumococcal conjugate vaccine (PCV7) against invasive pneumococcal disease (IPD) using the screening and case-control methods. Cases were children aged 19-35 months with pneumococcus isolated from normally sterile sites residing in Active Bacterial Core surveillance areas in the United States. Case-control VE was estimated for 2001-2004 by comparing the odds of vaccination among cases and community controls. Screening-method VE for 2001-2009 was estimated by comparing the proportion of cases vaccinated to National Immunization Survey-derived coverage among the general population. To evaluate the plausibility of screening-method VE findings, we estimated attack rates among vaccinated and unvaccinated persons. We identified 1,154 children with IPD. Annual population PCV7 coverage with ≥1 dose increased from 38% to 97%. Case-control VE for ≥1 dose was estimated as 75% against all-serotype IPD (annual range: 35-83%) and 91% for PCV7-type IPD (annual range: 65-100%). By the screening method, the overall VE was 86% for ≥1 dose (annual range: -240-70%) against all-serotype IPD and 94% (annual range: 62-97%) against PCV7-type IPD. As cases of PCV7-type IPD declined during 2001-2005, estimated attack rates for all-serotype IPD among vaccinated and unvaccinated individuals became less consistent than what would be expected with the estimated effectiveness of PCV7. The screening method yields estimates of VE that are highly dependent on the time period during which it is used and the choice of outcome. The method should be used cautiously to evaluate VE of PCVs.

Changing disparities in invasive pneumococcal disease by socioeconomic status and race/ ethnicity in Connecticut, 1998-2008.

OBJECTIVES: We compared invasive pneumococcal disease (IPD) incidence by race/ethnicity and neighborhood poverty level and assessed their relative utility to describe disparities in IPD in 1998-1999 and again in 2007-2008, after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). METHODS: We conducted laboratory surveillance for pneumococcal isolates from sterile body sites and serotyped the isolates. Home address was geocoded to the census-tract level. Census-tract data on the percentage of people below poverty were grouped into three categories. The difference in the magnitude of incidence by race/ethnicity and by census-tract socioeconomic status (SES) (high poverty minus low poverty) was compared for 1998-1999 and 2007-2008 for PCV7 and non-PCV7 serotypes. RESULTS: In 1998-1999, incidence difference (all per 100,000 population) for PCV7 serotypes for black people compared with white people was 14.3 and by poverty level was 13.9. The highest rate was among white people in high-poverty tracts (77.3). By 2007-2008, there were only slight differences between rates for black and white people (0.7) and SES (1.4). In 1998-1999, the incidence difference for non-PCV7 serotypes was 4.7 between black and white people and 6.0 by SES. By 2007-2008, the differences were 11.6 and 11.7, respectively. Among those living in the highest-poverty tracts, white people had the highest rate (42.9). CONCLUSIONS: In the absence of vaccine, IPD incidence is higher among people living in higher-poverty census tracts and among black people. Emerging serotypes also follow this trend. Differences in neighborhood poverty levels reveal disparities in rates of IPD as large as those seen by race/ethnicity and could be used to routinely describe disparities and target prevention.

Socioeconomic and racial/ethnic disparities in the incidence of bacteremic pneumonia among US adults.

OBJECTIVES: We examined associations between the socioeconomic characteristics of census tracts and racial/ethnic disparities in the incidence of bacteremic community-acquired pneumonia among US adults. METHODS: We analyzed data on 4870 adults aged 18 years or older with community-acquired bacteremic pneumonia identified through active, population-based surveillance in 9 states and geocoded to census tract of residence. We used data from the 2000 US Census to calculate incidence by age, race/ethnicity, and census tract characteristics and Poisson regression to estimate rate ratios (RRs) and 95% confidence intervals (CIs). RESULTS: During 2003 to 2004, the average annual incidence of bacteremic pneumonia was 24.2 episodes per 100 000 Black adults versus 10.1 per 100 000 White adults (RR = 2.40; 95% CI = 2.24, 2.57). Incidence among Black residents of census tracts with 20% or more of persons in poverty (most impoverished) was 4.4 times the incidence among White residents of census tracts with less than 5% of persons in poverty (least impoverished). Racial disparities in incidence were reduced but remained significant in models that controlled for age, census tract poverty level, and state. CONCLUSIONS: Adults living in impoverished census tracts are at increased risk of bacteremic pneumonia and should be targeted for prevention efforts.

Evaluating the potential public health impact of a Staphylococcus aureus vaccine through use of population-based surveillance for invasive methicillin-resistant S. aureus disease in the United States.

We evaluated the potential effects of a hypothetical vaccine in preventing invasive methicillin-resistant Staphylococcus aureus (MRSA) disease in the United States. Using an active, population-based surveillance program, we estimated baseline disease rates in the United States and compared three distinct vaccination strategies which targeted adults > or =65 years of age, persons at risk for recurrent invasive infection, and patients at hospital discharge. The strategies were projected to reduce the burden of invasive MRSA disease by 12.1%, 13.9% and 17.6%, respectively; with the strategy of vaccinating both adults > or =65 years of age and all adults at hospital discharge having the greatest impact per dose. Our data suggest that availability of an effective S. aureus vaccine could result in substantial reductions in invasive MRSA disease incidence. As candidate vaccines are evaluated, these data will be important in determining the optimal vaccination strategy.