Abstract
In 2005, meningococcal conjugate vaccine (MenACWY) was recommended for routine use among adolescents aged 11–18 years. This report describes the epidemiologic features of meningococcal disease and trends in meningococcal disease incidence following MenACWY introduction in the United States.
Incidence rates and case-fatality ratios by age group and serogroup during 2006–2015 were calculated using data from the National Notifiable Diseases Surveillance System (NNDSS); changes in incidence during this time were evaluated. Additionally, 20-year trends (1996–2015) in age- and race-standardized incidence were examined using data from Active Bacterial Core surveillance (ABCs).
During the years 2006–2015, 7924 cases of meningococcal disease were reported to NNDSS, resulting in an average annual incidence of 0.26 cases per 100000 population; 14.9% of cases were fatal. Among cases with serogroup information, 2290 (35.8%) were serogroup B, 1827 (28.5%) were serogroup Y, 1457 (22.8%) were serogroup C, 436 (6.8%) were serogroup W, and 392 (6.1%) were other serogroups. The incidence of serogroups A, C, W, and Y combined declined 76% among persons aged 11–20 years from 2006–2010 to 2011–2015 (P < .0001). From 1996 through 2015, the incidence of meningococcal disease declined among all age groups and predominant serogroups.
Declines in meningococcal disease incidence in the United States have been observed among all age groups and predominant serogroups (B, C, and Y). Reductions in the incidence of meningococcal disease due to serogroups A, C, W, and Y among adolescents suggest an impact of the MenACWY vaccine program in this age group.
Meningococcal disease, caused by the bacterium Neisseria meningitidis, is an important cause of bacterial meningitis and sepsis. It develops rapidly, typically in previously healthy people, and results in high morbidity and mortality. In the United States, the incidence of meningococcal disease has declined annually since a peak of disease in the late 1990s, and is currently at a historic low [1, 2].
In 2005, the first quadrivalent (serogroups A, C, W, and Y) meningococcal conjugate vaccine (MenACWY) was licensed, and recommended by the Advisory Committee on Immunization Practices (ACIP) for routine use in adolescents aged 11–18 years; in 2010 a booster dose was added for adolescents at 16 years of age to address concerns about waning immunity [1]. By 2015, vaccine coverage with ≥1 dose of MenACWY among adolescents aged 13–17 years had reached 81.3%; however, coverage with ≥2 doses of MenACWY among adolescents aged 17 years was only 33.3% [3].
Two serogroup B meningococcal (MenB) vaccines were licensed in 2014 and 2015 and approved for use in persons aged 10–25 years [4, 5]. In 2015, the ACIP recommended that adolescents and young adults aged 16–23 years may be vaccinated with a MenB vaccine to provide short-term protection against most strains of serogroup B meningococcal disease [6]. This recommendation for individual clinical decision making was made, in part, because of the current low incidence of meningococcal disease [6].
Surveillance for meningococcal disease is essential to monitor and evaluate changes in disease incidence, to understand the burden of meningococcal disease, and to inform meningococcal disease prevention activities and vaccine policy discussions. This report describes the epidemiologic features of meningococcal disease and trends in meningococcal disease incidence following MenACWY introduction in the United States.
METHODS
Surveillance
The Centers for Disease Control and Prevention (CDC) receives reports of meningococcal disease cases through 2 surveillance systems. Passive surveillance is conducted by all states and territories, and cases are reported electronically to CDC through the National Notifiable Diseases Surveillance System (NNDSS). In addition, active, population- and laboratory-based surveillance is conducted through Active Bacterial Core surveillance (ABCs), a component of the CDC’s Emerging Infections Program [7]. For this analysis we included meningococcal disease cases reported to NNDSS during 2006–2015 and ABCs during 1996–2015.
Information on meningococcal disease cases collected through NNDSS has historically been limited, with a high proportion of data either unknown or missing for key variables (eg, 49.2% of cases with unknown serogroup and 49.6% with missing/unknown case outcome). Since 2005, information for meningococcal disease cases has been supplemented in NNDSS using data from ABCs or data received directly from state health departments, improving the completeness of serogroup and outcome information to 81.0% and 83.1%, respectively; NNDSS data prior to 2006 were excluded from this analysis due to missing data for these key variables.
Cases reported through NNDSS were classified by state and local public health personnel according to the Council of State and Territorial Epidemiologists (CSTE) case definition. A confirmed case was defined as isolation of N. meningitidis from a normally sterile body site (eg, blood, cerebrospinal fluid [CSF]) or from purpuric lesions. A probable case was defined as detection of N. meningitidis–specific DNA in a specimen obtained from a normally sterile body site using a validated polymerase chain reaction (PCR) assay, or detection of N. meningitidis capsular polysaccharide antigen in formalin-fixed tissue by immunohistochemistry or in CSF by latex agglutination. Beginning in 2015, cases identified by PCR were considered confirmed cases. All cases classified as confirmed (n = 6843 [86.4%]), probable (n = 359 [4.5%]), or with an unknown case classification status (n = 722 [9.1%], all due to data transmission issues in California during 2006–2010) were included in this analysis.
The area under surveillance for N. meningitidis in ABCs included California (3 counties in the San Francisco Bay region, 1996–2015), Colorado (5 counties in the Denver metropolitan area, 2000–2015), Connecticut (statewide, 1996–2015), Georgia (8 counties, 1996; statewide, 1997–2015), Maryland (statewide, 1996–2015), Minnesota (statewide, 1996–2015), New Mexico (statewide, 2004–2015), New York (7 counties, 1997–1998; 15 counties in the Albany and Rochester areas, 1999–2015), Oregon (statewide, 1996–2015), and Tennessee (5 counties, 1996–1999, 11 counties, 2000–2009, 20 counties, 2010–2015). In 2015, the total population under surveillance was approximately 43.5 million, or 13.7% of the United States population. A case of meningococcal disease in ABCs was defined as the isolation of N. meningitidis from a normally sterile site (eg, blood, CSF) in a surveillance-area resident. Epidemiologic and clinical information was abstracted from medical records. Regular laboratory audits were conducted to identify cases missed during routine surveillance.
Laboratory Methods
Serogrouping of N. meningitidis isolates was performed at state public health laboratories. Isolates for cases reported through ABCs were sent to CDC, where slide agglutination serogrouping and serogroup-specific real-time polymerase chain reaction (real-time PCR) were performed [8, 9]. If the CDC slide agglutination or PCR testing confirmed the state serogroup result, that result was used as the final serogroup. If the CDC slide agglutination and PCR both differed from the state serogroup, the CDC result was used as the final serogroup. If an isolate was nonviable or contaminated on arrival at CDC after sending 2 times, the result from the state laboratory was used.
Statistical Analyses
Incidence rates were calculated using bridged-race population estimates produced by the US Census Bureau in collaboration with the National Center for Health Statistics as denominators. Population denominators by month of life for infants aged <1 year were calculated by dividing the population estimate for infants <1 year of age by 12. Incidence rates are reported as cases per 100000 population.
For trend analyses during 1996 through 2015, estimates of the number of cases in the 50 states were calculated from ABCs data, standardizing for age and race. Missing race data were multiply imputed by using sequential regression imputation methods [10]. For incidence rate calculations, an ABCs site was included only if data were collected for the complete year. Oregon has reported higher incidence rates of serogroup B and overall meningococcal disease because of hyperendemic serogroup B disease that was first reported in 1994 [11, 12]. Accordingly, incidence from the 9 ABCs sites (excluding Oregon) was standardized, by race and age group, to the United States population. Cases from Oregon were then added back to calculate the final standardized incidence rate and estimated annual burden of disease in the United States.
Statistical analysis was performed using SAS version 9.3 software (SAS Institute, Cary, North Carolina). Differences between proportions were tested using Pearson χ2 test or Fisher exact test. Differences in medians were assessed using the Wilcoxon rank-sum test.
RESULTS
Current Epidemiology: 2006–2015, National Notifiable Diseases Surveillance System Data
During the years 2006–2015, 7924 cases of meningococcal disease were reported in the United States, resulting in an average annual incidence of 0.26 per cases 100000 population; 14.9% of these cases were fatal. Incidence ranged from 0.13 cases per 100000 population to 0.79 cases per 100000 population (median, 0.25 cases per 100000) by state; incidence was highest in Oregon (0.79 cases per 100000 population). The incidence of serogroup B meningococcal disease was 0.31 cases per 100000 population in Oregon, compared to 0.07 per 100000 population in other states (P < .0001). Incidence varied by season, with more cases occurring during January (n = 870 [11.0%]), February (n = 917 [11.6%]), and March (n = 956 [12.1%]), and the fewest cases occurring during August (n = 422 [5.3%]) and September (n = 466 [5.9%]).
Table 1 shows the average annual cases, incidence, deaths, and case-fatality ratios associated with meningococcal disease by age group and serogroup during 2006–2015. Infants aged <1 year had the highest incidence of meningococcal disease (2.45 cases per 100000). Among cases in infants aged <1 year, nearly a quarter (n = 243 [24.8%]) of cases occurred among infants 2–3 months of age (3.64 cases per 100000). Case-fatality ratios were highest for serogroup W (20.9%) and serogroup C (20.2%), and lower among cases caused by serogroup B (11.5%) and serogroup Y (13.7%). Case-fatality ratios were highest among persons aged ≥85 years (28.0%) and decreased with lower age.
Average Annual Cases, Incidence (per 100000 Population), Deaths, and Case-Fatality Ratios Associated With Meningococcal Disease by Age Group and Serogroup, National Notifiable Diseases Surveillance System, United States, 2006–2015
| Age Group | Serogroup B | Serogroup C | Serogroup W | Serogroup Y | Total | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | |
| <1 y | 49 (1.22) | 4 | 9 (0.21) | 1 | 3 (0.08) | 0 | 14 (0.35) | 1 | 98 (2.45) | 7 (8.6) |
| 0–1 mo | 11 (1.60) | 1 | 1 (0.18) | 0 | 0 (0.01) | 0 | 2 (0.36) | 0 | 19 (2.77) | 2 (14.0) |
| 2–3 mo | 12 (1.83) | 1 | 2 (0.34) | 0 | 1 (0.13) | 0 | 3 (0.48) | 0 | 24 (3.64) | 1 (9.5) |
| 4–5 mo | 10 (1.44) | 1 | 1 (0.18) | 0 | 1 (0.09) | 0 | 3 (0.48) | 0 | 19 (2.77) | 1 (8.4) |
| 6–7 mo | 7 (1.06) | 0 | 2 (0.24) | 0 | 1 (0.09) | 0 | 2 (0.28) | 0 | 15 (2.26) | 0 (5.0) |
| 8–9 mo | 5 (0.78) | 0 | 2 (0.22) | 0 | 1 (0.10) | 0 | 2 (0.22) | 0 | 12 (1.81) | 1 (13.4) |
| 10–11 mo | 3 (0.51) | 1 | 1 (0.10) | 0 | 0 (0.03) | 0 | 2 (0.25) | 0 | 8 (1.21) | 1 (21.2) |
| 1 y | 16 (0.41) | 1 | 6 (0.15) | 0 | 2 (0.05) | 0 | 3 (0.08) | 0 | 36 (0.90) | 2 (5.9) |
| 2–4 y | 20 (0.16) | 2 | 9 (0.07) | 1 | 2 (0.01) | 0 | 3 (0.02) | 0 | 43 (0.35) | 4 (11.8) |
| 5–10 y | 12 (0.05) | 1 | 8 (0.03) | 1 | 1 (0.00) | 0 | 5 (0.02) | 1 | 34 (0.14) | 3 (10.5) |
| 11–15 y | 9 (0.04) | 0 | 5 (0.02) | 1 | 1 (0.00) | 0 | 6 (0.03) | 1 | 26 (0.12) | 3 (11.5) |
| 16–20 y | 33 (0.15) | 4 | 18 (0.08) | 3 | 2 (0.01) | 0 | 18 (0.08) | 2 | 91 (0.42) | 11 (14.3) |
| 21–25 y | 20 (0.09) | 2 | 16 (0.07) | 4 | 3 (0.01) | 1 | 10 (0.05) | 1 | 64 (0.29) | 9 (16.7) |
| 26–44 y | 28 (0.04) | 3 | 34 (0.04) | 8 | 7 (0.01) | 1 | 23 (0.03) | 3 | 120 (0.15) | 17 (16.8) |
| 45–64 y | 28 (0.03) | 3 | 25 (0.03) | 5 | 11 (0.01) | 2 | 42 (0.05) | 4 | 143 (0.18) | 20 (16.9) |
| 65–84 y | 11 (0.03) | 2 | 11 (0.03) | 2 | 10 (0.03) | 2 | 44 (0.12) | 6 | 101 (0.28) | 14 (17.4) |
| ≥85 y | 3 (0.06) | 1 | 4 (0.08) | 1 | 4 (0.08) | 1 | 15 (0.26) | 3 | 36 (0.63) | 8 (28.0) |
| Total | 229 (0.07) | 23 (11.5) | 146 (0.05) | 27 (20.2) | 44 (0.01) | 8 (20.9) | 183 (0.06) | 22 (13.7) | 792 (0.26) | 98 (14.9) |
| Age Group | Serogroup B | Serogroup C | Serogroup W | Serogroup Y | Total | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | |
| <1 y | 49 (1.22) | 4 | 9 (0.21) | 1 | 3 (0.08) | 0 | 14 (0.35) | 1 | 98 (2.45) | 7 (8.6) |
| 0–1 mo | 11 (1.60) | 1 | 1 (0.18) | 0 | 0 (0.01) | 0 | 2 (0.36) | 0 | 19 (2.77) | 2 (14.0) |
| 2–3 mo | 12 (1.83) | 1 | 2 (0.34) | 0 | 1 (0.13) | 0 | 3 (0.48) | 0 | 24 (3.64) | 1 (9.5) |
| 4–5 mo | 10 (1.44) | 1 | 1 (0.18) | 0 | 1 (0.09) | 0 | 3 (0.48) | 0 | 19 (2.77) | 1 (8.4) |
| 6–7 mo | 7 (1.06) | 0 | 2 (0.24) | 0 | 1 (0.09) | 0 | 2 (0.28) | 0 | 15 (2.26) | 0 (5.0) |
| 8–9 mo | 5 (0.78) | 0 | 2 (0.22) | 0 | 1 (0.10) | 0 | 2 (0.22) | 0 | 12 (1.81) | 1 (13.4) |
| 10–11 mo | 3 (0.51) | 1 | 1 (0.10) | 0 | 0 (0.03) | 0 | 2 (0.25) | 0 | 8 (1.21) | 1 (21.2) |
| 1 y | 16 (0.41) | 1 | 6 (0.15) | 0 | 2 (0.05) | 0 | 3 (0.08) | 0 | 36 (0.90) | 2 (5.9) |
| 2–4 y | 20 (0.16) | 2 | 9 (0.07) | 1 | 2 (0.01) | 0 | 3 (0.02) | 0 | 43 (0.35) | 4 (11.8) |
| 5–10 y | 12 (0.05) | 1 | 8 (0.03) | 1 | 1 (0.00) | 0 | 5 (0.02) | 1 | 34 (0.14) | 3 (10.5) |
| 11–15 y | 9 (0.04) | 0 | 5 (0.02) | 1 | 1 (0.00) | 0 | 6 (0.03) | 1 | 26 (0.12) | 3 (11.5) |
| 16–20 y | 33 (0.15) | 4 | 18 (0.08) | 3 | 2 (0.01) | 0 | 18 (0.08) | 2 | 91 (0.42) | 11 (14.3) |
| 21–25 y | 20 (0.09) | 2 | 16 (0.07) | 4 | 3 (0.01) | 1 | 10 (0.05) | 1 | 64 (0.29) | 9 (16.7) |
| 26–44 y | 28 (0.04) | 3 | 34 (0.04) | 8 | 7 (0.01) | 1 | 23 (0.03) | 3 | 120 (0.15) | 17 (16.8) |
| 45–64 y | 28 (0.03) | 3 | 25 (0.03) | 5 | 11 (0.01) | 2 | 42 (0.05) | 4 | 143 (0.18) | 20 (16.9) |
| 65–84 y | 11 (0.03) | 2 | 11 (0.03) | 2 | 10 (0.03) | 2 | 44 (0.12) | 6 | 101 (0.28) | 14 (17.4) |
| ≥85 y | 3 (0.06) | 1 | 4 (0.08) | 1 | 4 (0.08) | 1 | 15 (0.26) | 3 | 36 (0.63) | 8 (28.0) |
| Total | 229 (0.07) | 23 (11.5) | 146 (0.05) | 27 (20.2) | 44 (0.01) | 8 (20.9) | 183 (0.06) | 22 (13.7) | 792 (0.26) | 98 (14.9) |
Abbreviation: CFR, case-fatality ratio.
Average Annual Cases, Incidence (per 100000 Population), Deaths, and Case-Fatality Ratios Associated With Meningococcal Disease by Age Group and Serogroup, National Notifiable Diseases Surveillance System, United States, 2006–2015
| Age Group | Serogroup B | Serogroup C | Serogroup W | Serogroup Y | Total | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | |
| <1 y | 49 (1.22) | 4 | 9 (0.21) | 1 | 3 (0.08) | 0 | 14 (0.35) | 1 | 98 (2.45) | 7 (8.6) |
| 0–1 mo | 11 (1.60) | 1 | 1 (0.18) | 0 | 0 (0.01) | 0 | 2 (0.36) | 0 | 19 (2.77) | 2 (14.0) |
| 2–3 mo | 12 (1.83) | 1 | 2 (0.34) | 0 | 1 (0.13) | 0 | 3 (0.48) | 0 | 24 (3.64) | 1 (9.5) |
| 4–5 mo | 10 (1.44) | 1 | 1 (0.18) | 0 | 1 (0.09) | 0 | 3 (0.48) | 0 | 19 (2.77) | 1 (8.4) |
| 6–7 mo | 7 (1.06) | 0 | 2 (0.24) | 0 | 1 (0.09) | 0 | 2 (0.28) | 0 | 15 (2.26) | 0 (5.0) |
| 8–9 mo | 5 (0.78) | 0 | 2 (0.22) | 0 | 1 (0.10) | 0 | 2 (0.22) | 0 | 12 (1.81) | 1 (13.4) |
| 10–11 mo | 3 (0.51) | 1 | 1 (0.10) | 0 | 0 (0.03) | 0 | 2 (0.25) | 0 | 8 (1.21) | 1 (21.2) |
| 1 y | 16 (0.41) | 1 | 6 (0.15) | 0 | 2 (0.05) | 0 | 3 (0.08) | 0 | 36 (0.90) | 2 (5.9) |
| 2–4 y | 20 (0.16) | 2 | 9 (0.07) | 1 | 2 (0.01) | 0 | 3 (0.02) | 0 | 43 (0.35) | 4 (11.8) |
| 5–10 y | 12 (0.05) | 1 | 8 (0.03) | 1 | 1 (0.00) | 0 | 5 (0.02) | 1 | 34 (0.14) | 3 (10.5) |
| 11–15 y | 9 (0.04) | 0 | 5 (0.02) | 1 | 1 (0.00) | 0 | 6 (0.03) | 1 | 26 (0.12) | 3 (11.5) |
| 16–20 y | 33 (0.15) | 4 | 18 (0.08) | 3 | 2 (0.01) | 0 | 18 (0.08) | 2 | 91 (0.42) | 11 (14.3) |
| 21–25 y | 20 (0.09) | 2 | 16 (0.07) | 4 | 3 (0.01) | 1 | 10 (0.05) | 1 | 64 (0.29) | 9 (16.7) |
| 26–44 y | 28 (0.04) | 3 | 34 (0.04) | 8 | 7 (0.01) | 1 | 23 (0.03) | 3 | 120 (0.15) | 17 (16.8) |
| 45–64 y | 28 (0.03) | 3 | 25 (0.03) | 5 | 11 (0.01) | 2 | 42 (0.05) | 4 | 143 (0.18) | 20 (16.9) |
| 65–84 y | 11 (0.03) | 2 | 11 (0.03) | 2 | 10 (0.03) | 2 | 44 (0.12) | 6 | 101 (0.28) | 14 (17.4) |
| ≥85 y | 3 (0.06) | 1 | 4 (0.08) | 1 | 4 (0.08) | 1 | 15 (0.26) | 3 | 36 (0.63) | 8 (28.0) |
| Total | 229 (0.07) | 23 (11.5) | 146 (0.05) | 27 (20.2) | 44 (0.01) | 8 (20.9) | 183 (0.06) | 22 (13.7) | 792 (0.26) | 98 (14.9) |
| Age Group | Serogroup B | Serogroup C | Serogroup W | Serogroup Y | Total | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | No. of Cases (Incidence) | No. of Deaths (CFR) | |
| <1 y | 49 (1.22) | 4 | 9 (0.21) | 1 | 3 (0.08) | 0 | 14 (0.35) | 1 | 98 (2.45) | 7 (8.6) |
| 0–1 mo | 11 (1.60) | 1 | 1 (0.18) | 0 | 0 (0.01) | 0 | 2 (0.36) | 0 | 19 (2.77) | 2 (14.0) |
| 2–3 mo | 12 (1.83) | 1 | 2 (0.34) | 0 | 1 (0.13) | 0 | 3 (0.48) | 0 | 24 (3.64) | 1 (9.5) |
| 4–5 mo | 10 (1.44) | 1 | 1 (0.18) | 0 | 1 (0.09) | 0 | 3 (0.48) | 0 | 19 (2.77) | 1 (8.4) |
| 6–7 mo | 7 (1.06) | 0 | 2 (0.24) | 0 | 1 (0.09) | 0 | 2 (0.28) | 0 | 15 (2.26) | 0 (5.0) |
| 8–9 mo | 5 (0.78) | 0 | 2 (0.22) | 0 | 1 (0.10) | 0 | 2 (0.22) | 0 | 12 (1.81) | 1 (13.4) |
| 10–11 mo | 3 (0.51) | 1 | 1 (0.10) | 0 | 0 (0.03) | 0 | 2 (0.25) | 0 | 8 (1.21) | 1 (21.2) |
| 1 y | 16 (0.41) | 1 | 6 (0.15) | 0 | 2 (0.05) | 0 | 3 (0.08) | 0 | 36 (0.90) | 2 (5.9) |
| 2–4 y | 20 (0.16) | 2 | 9 (0.07) | 1 | 2 (0.01) | 0 | 3 (0.02) | 0 | 43 (0.35) | 4 (11.8) |
| 5–10 y | 12 (0.05) | 1 | 8 (0.03) | 1 | 1 (0.00) | 0 | 5 (0.02) | 1 | 34 (0.14) | 3 (10.5) |
| 11–15 y | 9 (0.04) | 0 | 5 (0.02) | 1 | 1 (0.00) | 0 | 6 (0.03) | 1 | 26 (0.12) | 3 (11.5) |
| 16–20 y | 33 (0.15) | 4 | 18 (0.08) | 3 | 2 (0.01) | 0 | 18 (0.08) | 2 | 91 (0.42) | 11 (14.3) |
| 21–25 y | 20 (0.09) | 2 | 16 (0.07) | 4 | 3 (0.01) | 1 | 10 (0.05) | 1 | 64 (0.29) | 9 (16.7) |
| 26–44 y | 28 (0.04) | 3 | 34 (0.04) | 8 | 7 (0.01) | 1 | 23 (0.03) | 3 | 120 (0.15) | 17 (16.8) |
| 45–64 y | 28 (0.03) | 3 | 25 (0.03) | 5 | 11 (0.01) | 2 | 42 (0.05) | 4 | 143 (0.18) | 20 (16.9) |
| 65–84 y | 11 (0.03) | 2 | 11 (0.03) | 2 | 10 (0.03) | 2 | 44 (0.12) | 6 | 101 (0.28) | 14 (17.4) |
| ≥85 y | 3 (0.06) | 1 | 4 (0.08) | 1 | 4 (0.08) | 1 | 15 (0.26) | 3 | 36 (0.63) | 8 (28.0) |
| Total | 229 (0.07) | 23 (11.5) | 146 (0.05) | 27 (20.2) | 44 (0.01) | 8 (20.9) | 183 (0.06) | 22 (13.7) | 792 (0.26) | 98 (14.9) |
Abbreviation: CFR, case-fatality ratio.
Sex was available for 7873 (99.4%) cases; males accounted for 3982 (50.6%) cases and females 3891 (49.4%) cases. Female patients were significantly older than male patients (median age, 35 years in female patients vs 22 years in male patients; P < .0001). Overall, the incidence was similar for male (0.26 cases per 100000) and female (0.25 cases per 100000) patients (P < .01); however, among infants aged <1 year, incidence was higher among males (2.86 cases per 100000) compared to females (1.99 cases per 100000) (P < .0001) and conversely, among persons aged 65–84 years and ≥85 years, incidence was higher among females (0.34 and 0.75 cases per 100000, respectively) compared with males (0.20 and 0.38 cases per 100000, respectively) (P < .0001).
Information on race was available for 6491 (81.9%) case patients; 4922 (75.8%) cases occurred among white patients, 1130 (17.4%) among black patients, and 439 (6.8%) cases among patients of other racial groups. The incidence of meningococcal disease among black persons was 0.27 cases per 100000 compared with 0.20 cases per 100000 among white persons (P < .0001) and 0.20 cases per 100000 among other race groups combined.
Serogroup information was available for 6402 (80.8%) cases; 2290 (35.8%) were serogroup B, 1827 (28.5%) were serogroup Y, 1457 (22.8%) were serogroup C, 436 (6.8%) were serogroup W, and 392 (6.1%) were other serogroups (including nongroupables).
Trends in Meningococcal Disease Incidence: 2006–2015, National Notifiable Diseases Surveillance System Data
Annual incidence decreased 70.8% (P < .0001) from 0.40 cases per 100000 population in 2006 to 0.12 cases per 100000 population in 2015. In 2006, the incidence of serogroup B meningococcal disease in Oregon was 0.38 cases per 100000 population, compared with 0.11 cases per 100000 population in the other states (P < .0001); in 2015, incidence was 0.35 cases per 100000 population in Oregon and 0.05 cases per 100000 population in other states (P < .0001).
During 2006–2015, 2124 cases were reported in persons 11–29 years of age; incidence peaked among adolescents aged 18 (0.55 per 100000) and 19 (0.51 cases per 100000) years. The incidence of both serogroups A, C, W, and Y combined and serogroup B declined among persons aged 11–15 and 16–20 years from 2006–2007 to 2014–2015 (Table 2). Among persons aged 11–20 years—the age group routinely recommended to receive MenACWY conjugate vaccine—the largest declines were observed for serogroups A, C, W, and Y combined (Figure 1A and Table 2). Smaller declines were observed for serogroup B among persons aged 11–20 years (Figure 1B and Table 2). Declines in the incidence of serogroups A, C, W, and Y combined were also observed among other age groups, particularly in the youngest and oldest age groups (Figure 2A). Similar declines were not observed for serogroup B (Figure 2B).
Meningococcal Disease Cases, Incidence, and Percentage Change by Age Group and Serogroup, National Notifiable Diseases Surveillance System, United States, 2006–2015
| Serogroup | Age, y | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | 2014–2015 | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Change a | No. of Cases (Incidence) | % Change a | ||
| Serogroups A, C, W, Y | <1 | 86 (1.05) | … | 69 (0.85) | –19.8 | 52 (0.66) | –39.5 | 35 (0.45) | –59.3 | 16 (0.20) | –81.4 |
| 11–15 | 55 (0.13) | … | 41 (0.10) | –25.5 | 8 (0.02) | –85.5 | 6 (0.01) | –89.1 | 3 (0.01) | –94.5 | |
| 16–20 | 143 (0.33) | … | 102 (0.23) | –28.7 | 84 (0.19) | –41.3 | 34 (0.08) | –76.2 | 11 (0.03) | –92.3 | |
| >20 | 634 (0.15) | … | 671 (0.15) | +5.8 | 598 (0.13) | –5.7 | 434 (0.10) | –31.5 | 281 (0.06) | –55.7 | |
| Serogroup B | <1 | 142 (1.73) | … | 128 (1.57) | –9.9 | 104 (1.31) | –26.8 | 60 (0.76) | –57.7 | 55 (0.69) | –61.3 |
| 11–15 | 26 (0.06) | … | 23 (0.06) | –11.5 | 12 (0.03) | –53.8 | 14 (0.03) | –46.2 | 11 (0.03) | –57.7 | |
| 16–20 | 82 (0.19) | … | 88 (0.20) | +7.3 | 59 (0.13) | –28.0 | 56 (0.13) | –31.7 | 45 (0.11) | –45.1 | |
| >20 | 205 (0.05) | … | 246 (0.06) | +20.0 | 173 (0.04) | –15.6 | 127 (0.03) | –38.0 | 148 (0.03) | –27.8 | |
| Serogroup | Age, y | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | 2014–2015 | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Change a | No. of Cases (Incidence) | % Change a | ||
| Serogroups A, C, W, Y | <1 | 86 (1.05) | … | 69 (0.85) | –19.8 | 52 (0.66) | –39.5 | 35 (0.45) | –59.3 | 16 (0.20) | –81.4 |
| 11–15 | 55 (0.13) | … | 41 (0.10) | –25.5 | 8 (0.02) | –85.5 | 6 (0.01) | –89.1 | 3 (0.01) | –94.5 | |
| 16–20 | 143 (0.33) | … | 102 (0.23) | –28.7 | 84 (0.19) | –41.3 | 34 (0.08) | –76.2 | 11 (0.03) | –92.3 | |
| >20 | 634 (0.15) | … | 671 (0.15) | +5.8 | 598 (0.13) | –5.7 | 434 (0.10) | –31.5 | 281 (0.06) | –55.7 | |
| Serogroup B | <1 | 142 (1.73) | … | 128 (1.57) | –9.9 | 104 (1.31) | –26.8 | 60 (0.76) | –57.7 | 55 (0.69) | –61.3 |
| 11–15 | 26 (0.06) | … | 23 (0.06) | –11.5 | 12 (0.03) | –53.8 | 14 (0.03) | –46.2 | 11 (0.03) | –57.7 | |
| 16–20 | 82 (0.19) | … | 88 (0.20) | +7.3 | 59 (0.13) | –28.0 | 56 (0.13) | –31.7 | 45 (0.11) | –45.1 | |
| >20 | 205 (0.05) | … | 246 (0.06) | +20.0 | 173 (0.04) | –15.6 | 127 (0.03) | –38.0 | 148 (0.03) | –27.8 | |
Cases in 2006–2007 used as the reference group for calculations of percentage change.
Meningococcal Disease Cases, Incidence, and Percentage Change by Age Group and Serogroup, National Notifiable Diseases Surveillance System, United States, 2006–2015
| Serogroup | Age, y | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | 2014–2015 | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Change a | No. of Cases (Incidence) | % Change a | ||
| Serogroups A, C, W, Y | <1 | 86 (1.05) | … | 69 (0.85) | –19.8 | 52 (0.66) | –39.5 | 35 (0.45) | –59.3 | 16 (0.20) | –81.4 |
| 11–15 | 55 (0.13) | … | 41 (0.10) | –25.5 | 8 (0.02) | –85.5 | 6 (0.01) | –89.1 | 3 (0.01) | –94.5 | |
| 16–20 | 143 (0.33) | … | 102 (0.23) | –28.7 | 84 (0.19) | –41.3 | 34 (0.08) | –76.2 | 11 (0.03) | –92.3 | |
| >20 | 634 (0.15) | … | 671 (0.15) | +5.8 | 598 (0.13) | –5.7 | 434 (0.10) | –31.5 | 281 (0.06) | –55.7 | |
| Serogroup B | <1 | 142 (1.73) | … | 128 (1.57) | –9.9 | 104 (1.31) | –26.8 | 60 (0.76) | –57.7 | 55 (0.69) | –61.3 |
| 11–15 | 26 (0.06) | … | 23 (0.06) | –11.5 | 12 (0.03) | –53.8 | 14 (0.03) | –46.2 | 11 (0.03) | –57.7 | |
| 16–20 | 82 (0.19) | … | 88 (0.20) | +7.3 | 59 (0.13) | –28.0 | 56 (0.13) | –31.7 | 45 (0.11) | –45.1 | |
| >20 | 205 (0.05) | … | 246 (0.06) | +20.0 | 173 (0.04) | –15.6 | 127 (0.03) | –38.0 | 148 (0.03) | –27.8 | |
| Serogroup | Age, y | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | 2014–2015 | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Changea | No. of Cases (Incidence) | % Change a | No. of Cases (Incidence) | % Change a | ||
| Serogroups A, C, W, Y | <1 | 86 (1.05) | … | 69 (0.85) | –19.8 | 52 (0.66) | –39.5 | 35 (0.45) | –59.3 | 16 (0.20) | –81.4 |
| 11–15 | 55 (0.13) | … | 41 (0.10) | –25.5 | 8 (0.02) | –85.5 | 6 (0.01) | –89.1 | 3 (0.01) | –94.5 | |
| 16–20 | 143 (0.33) | … | 102 (0.23) | –28.7 | 84 (0.19) | –41.3 | 34 (0.08) | –76.2 | 11 (0.03) | –92.3 | |
| >20 | 634 (0.15) | … | 671 (0.15) | +5.8 | 598 (0.13) | –5.7 | 434 (0.10) | –31.5 | 281 (0.06) | –55.7 | |
| Serogroup B | <1 | 142 (1.73) | … | 128 (1.57) | –9.9 | 104 (1.31) | –26.8 | 60 (0.76) | –57.7 | 55 (0.69) | –61.3 |
| 11–15 | 26 (0.06) | … | 23 (0.06) | –11.5 | 12 (0.03) | –53.8 | 14 (0.03) | –46.2 | 11 (0.03) | –57.7 | |
| 16–20 | 82 (0.19) | … | 88 (0.20) | +7.3 | 59 (0.13) | –28.0 | 56 (0.13) | –31.7 | 45 (0.11) | –45.1 | |
| >20 | 205 (0.05) | … | 246 (0.06) | +20.0 | 173 (0.04) | –15.6 | 127 (0.03) | –38.0 | 148 (0.03) | –27.8 | |
Cases in 2006–2007 used as the reference group for calculations of percentage change.
Changes in the incidence of serogroups A, C, W, Y combined (A) and serogroup B (B) among adolescents from 2006–2010 to 2011–2015, National Notifiable Diseases Surveillance System, United States, 2006–2015.
Changes in the incidence of serogroups A, C, W, Y combined (A) and serogroup B (B) among all age groups from 2006–2010 to 2011–2015, National Notifiable Diseases Surveillance System, United States, 2006–2015.
Trends in Meningococcal Disease Incidence: 1996–2015, Active Bacterial Core Surveillance Data
During 1996–2015, 3722 cases of meningococcal disease were reported from ABCs sites. During this time, N. meningitidis incidence declined among all age groups (Figure 3A); the largest declines in incidence were observed among infants aged <1 year where incidence decreased from 11.04 cases per 100000 in 1996 to 0.73 cases per 100000 in 2015 (93% decrease). During the study period, the median age of patients increased significantly. In 1996 the median patient age was 17 years (range, 0–93 years), and 30.1% of patients were aged <5 years, whereas in 2015, the median patient age had increased to 42 years (range, 0–98 years), and 15.3% of patients were <5 years of age.
Trends in meningococcal disease incidence, by age group (A), serogroup (B), and race (C), estimated from Active Bacterial Core surveillance, United States, 1996–2015.
Overall, 93.3% of cases had serogroup information available. Figure 3B shows trends in the incidence of meningococcal disease by serogroup; the incidence of serogroups B, C, and Y all declined during the study period while the incidence of serogroup W and other serogroups remained relatively stable. The incidence of serogroup B declined from 0.25 cases per 100000 in 1996 to 0.05 cases per 100000 in 2015 (80% decrease); serogroup C declined from 0.38 cases per 100000 to 0.01 cases per 100000 (97% decrease); and serogroup Y declined from 0.41 cases per 100000 to 0.02 cases per 100000 (95% decrease). Differences in the incidence of meningococcal disease by race also diminished during the study period (Figure 3C).
DISCUSSION
The incidence of meningococcal disease has steadily declined in the United States over the last 2 decades. Decreases in the incidence of serogroups, B, C, and Y, the predominant disease-associated serogroups in the United States, are responsible for the reduction in burden of meningococcal disease across all age groups. The higher incidence of serogroup B and overall meningococcal disease in Oregon compared with other states has continued to persist, although incidence of meningococcal disease in Oregon has declined overall. In this analysis, the case-fatality ratios (Table 1) observed among many groups are higher than has been previously reported [2]. This could be due to the shift toward an older median age of meningococcal disease cases observed during the past 20 years, as the case-fatality ratio tends to be higher among adults.
CDC receives reports of meningococcal disease cases through 2 surveillance systems, NNDSS and ABCs, and these surveillance systems have important differences between them. NNDSS is a passive surveillance system that covers all of the United States and collects reports of both probable and confirmed cases of meningococcal disease, including cases identified by PCR. ABCs is an active laboratory-and population-based surveillance system that covers approximately 15% of the US population and collects reports of culture confirmed cases only. In 2012, CDC compared meningococcal disease surveillance through NNDSS and ABCs, and found that ABCs did not substantially underestimate the number of cases of meningococcal disease because only a small proportion of cases were identified by PCR testing [13].
ABCs has historically been the primary source of data for meningococcal disease surveillance in the United States because it has provided more complete and detailed information on meningococcal disease cases occurring the ABCs surveillance area, and those cases could be used to estimate US incidence. However, as the number of meningococcal disease cases has fallen, a shift toward a more integrated approach to surveillance has been necessary. Completeness of meningococcal disease case reporting through NNDSS is thought to be high given the need for prompt public health follow-up around suspected cases. Additional efforts have been made in recent years to collect more information on cases reported through NNDSS, including complete information for key variables (ie, serogroup, outcome) necessary to monitor meningococcal disease epidemiology and inform vaccine policy decisions in the United States; ABCs data remains important for monitoring meningococcal disease trends over time.
The most dramatic declines in incidence were observed among infants aged <1 year, an age group that is not targeted for meningococcal vaccination in the United States. The reasons for the declines in incidence observed over the last 20 years among infants aged <1 year are unclear, and are unlikely to be driven by MenACWY vaccination of adolescents as many of these declines occurred prior to MenACWY vaccination in the United States, and large declines in serogroup B were also observed. Although it does not appear the adolescent meningococcal vaccination program has resulted in any significant indirect benefits in other age groups at this time, these data are the first to suggest an impact of the adolescent MenACWY program in reducing rates of serogroups A, C, W, and Y among adolescents. The largest declines in serogroups A, C, W, and Y have been observed in younger adolescents, possibly due to high vaccination coverage in that age group. These data also highlight the remaining burden of serogroups C and Y among adolescents, which are likely associated with not receiving MenACWY vaccine, or not receiving the MenACWY booster dose in late adolescence. While the incidence of serogroup B meningococcal disease also declined during this time period, the declines in incidence have been smaller than those observed for serogroups A, C, W, and Y, and appear to have slowed in the most recent years (Table 2).
Due in part to the current low incidence of meningococcal disease in the United States, the ACIP recently did not recommend routine vaccination of infants with MenACWY, and more recently the ACIP did not make a routine recommendation for use of MenB vaccines in adolescents, rather recommending individual clinical decision making for the use of MenB vaccines in adolescents and young adults aged 16–23 years. In recent years, efforts have been made to ensure that meningococcal disease surveillance data are complete, representative, and of the highest quality possible, and as such these data will continue to be used to monitor current vaccination recommendations and inform future vaccine policy decisions in the United States.
Notes
Acknowledgments. The authors give special thanks to the state and local health departments and Active Bacterial Core surveillance sites who provided surveillance data and isolates from meningococcal cases for this analysis, and the Centers for Disease Control and Prevention (CDC) Bacterial Meningitis Lab for technical assistance.
Disclaimer. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC.
Financial support. This work was supported by the CDC.
Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
References
