Development of COVID-19 vaccine policy - United States, 2020-2023.

COVID-19 vaccines represent a great scientific and public health achievement in the face of overwhelming pressures from a global pandemic, preventing millions of hospitalizations and deaths due to COVID-19 vaccines in the United States. Over 675 million doses of COVID-19 vaccines have been administered in the United States, and over 80% of the U.S. population has had at least 1 dose of a COVID-19 vaccine. Over the course of the COVID-19 pandemic in the United States, over one million people died from COVID-19, and over six million were hospitalized. It has been estimated that COVID-19 vaccines prevented more than 18 million additional hospitalizations and more than 3 million additional deaths due to COVID-19 in the United States. From the beginning of the COVID-19 pandemic in 2020 through June 2023, ACIP had 35 COVID-19 focused meetings and 24 votes for COVID-19 vaccine recommendations. ACIP had the critical task of rapidly and thoroughly reviewing emerging and evolving data on COVID-19 epidemiology and vaccines, as well as making comprehensive population-based recommendations for vaccine policy and considerations for implementation through a transparent and evidence-based framework. Safe and effective COVID-19 vaccines, recommended through transparent policy discussions with ACIP, remain the best tool we have to prevent serious illness, hospitalization and death from COVID-19.

The Advisory Committee on Immunization Practices' Interim Recommendation for Use of Pfizer-BioNTech COVID-19 Vaccine in Adolescents Aged 12-15 Years - United States, May 2021.

The Pfizer-BioNTech COVID-19 (BNT162b2) vaccine is a lipid nanoparticle-formulated, nucleoside-modified mRNA vaccine encoding the prefusion spike glycoprotein of SARS-CoV-2, the virus that causes COVID-19. Vaccination with the Pfizer-BioNTech COVID-19 vaccine consists of 2 intramuscular doses (30 µg, 0.3 mL each) administered 3 weeks apart. On December 11, 2020, the Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for use of the Pfizer-BioNTech COVID-19 vaccine (Pfizer, Inc; Philadelphia, Pennsylvania) in persons aged ≥16 years (1); on December 12, 2020, the Advisory Committee on Immunization Practices (ACIP) issued an interim recommendation for use of the vaccine in the same age group (2). As of May 12, 2021, approximately 141.6 million doses of the Pfizer-BioNTech COVID-19 vaccine had been administered to persons aged ≥16 years.* On May 10, 2021, FDA expanded the EUA for the Pfizer-BioNTech COVID-19 vaccine to include adolescents aged 12-15 years (1). On May 12, 2021, ACIP issued an interim recommendation† for use of the Pfizer-BioNTech COVID-19 vaccine in adolescents aged 12-15 years for the prevention of COVID-19. To guide its deliberations regarding the vaccine, ACIP used the Evidence to Recommendation (EtR) Framework,§ using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.¶ The ACIP recommendation for the use of the Pfizer-BioNTech COVID-19 vaccine in persons aged ≥12 years under an EUA is interim and will be updated as additional information becomes available.

Updated Recommendations from the Advisory Committee on Immunization Practices for Use of the Janssen (Johnson & Johnson) COVID-19 Vaccine After Reports of Thrombosis with Thrombocytopenia Syndrome Among Vaccine Recipients - United States, April 2021.

On February 27, 2021, the Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for the Janssen COVID-19 (Ad.26.COV2.S) vaccine (Janssen Biotech, Inc., a Janssen Pharmaceutical company, Johnson & Johnson; New Brunswick, New Jersey), and on February 28, 2021, the Advisory Committee on Immunization Practices (ACIP) issued interim recommendations for its use in persons aged ≥18 years (1,2). On April 13, 2021, CDC and FDA recommended a pause in the use of the Janssen COVID-19 vaccine after reports of six U.S. cases of cerebral venous sinus thrombosis (CVST) with thrombocytopenia, a rare thromboembolic syndrome, among Janssen COVID-19 vaccine recipients (3). Two emergency ACIP meetings were rapidly convened to review reported cases of thrombosis with thrombocytopenia syndrome (TTS) and to consider updated recommendations for use of the Janssen COVID-19 vaccine in the United States. On April 23, 2021, after a discussion of the benefits and risks of resuming vaccination, ACIP reaffirmed its interim recommendation for use of the Janssen COVID-19 vaccine in all persons aged ≥18 years under the FDA's EUA, which now includes a warning that rare clotting events might occur after vaccination, primarily among women aged 18-49 years. Patient and provider education about the risk for TTS with the Janssen COVID-19 vaccine, especially among women aged <50 years, as well as the availability of alternative COVID-19 vaccines, is required to guide vaccine decision-making and ensure early recognition and clinical management of TTS.

Evaluation of meningococcal vaccination policies among colleges and universities - United States, 2017.

ObjectiveQuadrivalent meningococcal conjugate vaccines (MenACWY) have been recommended routinely for adolescents since 2005; in 2015, serogroup B meningococcal (MenB) vaccines were recommended for persons aged 16-23 years based on individual clinical decision making. We surveyed college health providers or administrators to understand current meningococcal vaccine policies. Methods/Participants: In January 2017, we distributed a survey to 985 institutions in partnership with the American College Health Association to assess vaccination policies and outbreak response plans. Results: Overall, 352 (36%) institutions completed the survey. Most either required (N = 186, 53%) or recommended (N = 148, 42%) a meningococcal vaccine; only half (N = 167) had a policy specifically addressing MenB vaccines. Few institutions with a MenB vaccine policy required vaccination (N = 7, 4%); most recommended vaccination (N = 160, 96%). Conclusion: Most institutions have a meningococcal vaccination policy; however, there is substantial diversity in policies. Fewer schools have policies specifically addressing MenB vaccines.

Incidence of Meningococcal Disease Before and After Implementation of Quadrivalent Meningococcal Conjugate Vaccine in the United States.

Importance: In 2005, the US Advisory Committee on Immunization Practices recommended routine quadrivalent meningococcal conjugate (MenACWY) vaccine for all adolescents aged 11 to 12 years, and in 2010, a booster dose for adolescents aged 16 years. Measuring the association between MenACWY vaccination and the incidence of meningococcal disease in adolescents is critical for evaluating the adolescent vaccination program and informing future vaccine policy. Objective: To describe the association between MenACWY vaccination and the incidence of meningococcal disease in US adolescents. Design, Setting, and Participants: In this cohort study, analysis of surveillance data included all confirmed and probable cases of Neisseria meningitidis reported to the National Notifiable Diseases Surveillance System from January 1, 2000, to December 31, 2017. Statistical analysis was conducted from October 1, 2018, to August 31, 2019. Exposures: Routine MenACWY vaccination among US adolescents. Main Outcomes and Measures: Poisson segmented regression analysis was used to model the annual incidence of meningococcal disease among adolescents aged 11 to 15 years and 16 to 22 years before the introduction of the MenACWY vaccine (2000-2005), after the primary dose recommendation (2006-2010), and after the booster dose recommendation (2011-2017); 95% CIs were used to determine significant differences between time periods. Results: The national incidence of meningococcal disease declined from 0.61 cases per 100 000 population during the prevaccine period (2000-2005) to 0.15 cases per 100 000 population during the post-booster dose period (2011-2017). The greatest percentage decline was observed for serogroup C, W, and Y combined (CWY) among adolescents aged 11 to 15 years and 16 to 22 years in the periods after vaccine introduction. Incidence of serogroup CWY meningococcal disease among adolescents aged 11 to 15 years decreased by 16.3% (95% CI, 12.1%-20.3%) annually during the prevaccine period and 27.8% (95% CI, 20.6%-34.4%) during the post-primary dose period (P = .02); among adolescents aged 16 to 22 years, the incidence decreased by 10.6% (95% CI, 6.8%-14.3%) annually in the post-primary dose period and 35.6% (95% CI, 29.3%-41.0%) annually in the post-booster dose period (P < .001). An estimated 222 cases of meningococcal disease due to serogroup CWY among adolescents were averted through vaccination during the evaluation period. Conclusions and Relevance: After introduction of a primary and booster MenACWY dose, the rates of decline in incidence of meningococcal disease due to serogroup C, W, or Y accelerated nearly 2-fold to 3-fold in vaccinated adolescent age groups. Although the MenACWY vaccine alone cannot explain the decline of meningococcal disease in the United States, these data suggest that MenACWY vaccination is associated with reduced disease rates in adolescents.

Carriage of Neisseria meningitidis in Men Who Have Sex With Men Presenting to Public Sexual Health Clinics, New York City.

BACKGROUND: We conducted a Neisseria meningitidis (Nm) carriage study among men who have sex with men (MSM) to explore possible sexual transmission. METHODS: We paired information on patient characteristics with oropharyngeal, rectal, and urethral Nm culture results to assess associations with Nm carriage among 706 MSM at New York City sexual health clinics. The Nm isolates were characterized by whole genome sequencing. RESULTS: Twenty-three percent (163 of 706) of MSM were Nm carriers. Oropharyngeal carriage was 22.6% (159 of 703), rectal 0.9% (6 of 695), and urethral 0.4% (3 of 696). Oropharyngeal carriage was associated with the following recent (past 30 days) exposures: 3 or more men kissed (adjusted relative risk [aRR], 1.38; 95% confidence interval [CI], 1.03-1.86), performing oral sex (aRR, 1.81; 95% CI, 1.04-3.18), and antibiotic use (aRR, 0.33; 95% CI, 0.19-0.57). Sixteen clonal complexes were identified; 27% belonged to invasive lineages. CONCLUSIONS: Our findings suggest that oral sex and the number of recent kissing partners contribute to Nm carriage in MSM.

Meningococcal Vaccination: Recommendations of the Advisory Committee on Immunization Practices, United States, 2020.

This report compiles and summarizes all recommendations from CDC's Advisory Committee on Immunization Practices (ACIP) for use of meningococcal vaccines in the United States. As a comprehensive summary and update of previously published recommendations, it replaces all previously published reports and policy notes. This report also contains new recommendations for administration of booster doses of serogroup B meningococcal (MenB) vaccine for persons at increased risk for serogroup B meningococcal disease. These guidelines will be updated as needed on the basis of availability of new data or licensure of new meningococcal vaccines. ACIP recommends routine vaccination with a quadrivalent meningococcal conjugate vaccine (MenACWY) for adolescents aged 11 or 12 years, with a booster dose at age 16 years. ACIP also recommends routine vaccination with MenACWY for persons aged ≥2 months at increased risk for meningococcal disease caused by serogroups A, C, W, or Y, including persons who have persistent complement component deficiencies; persons receiving a complement inhibitor (e.g., eculizumab [Soliris] or ravulizumab [Ultomiris]); persons who have anatomic or functional asplenia; persons with human immunodeficiency virus infection; microbiologists routinely exposed to isolates of Neisseria meningitidis; persons identified to be at increased risk because of a meningococcal disease outbreak caused by serogroups A, C, W, or Y; persons who travel to or live in areas in which meningococcal disease is hyperendemic or epidemic; unvaccinated or incompletely vaccinated first-year college students living in residence halls; and military recruits. ACIP recommends MenACWY booster doses for previously vaccinated persons who become or remain at increased risk.In addition, ACIP recommends routine use of MenB vaccine series among persons aged ≥10 years who are at increased risk for serogroup B meningococcal disease, including persons who have persistent complement component deficiencies; persons receiving a complement inhibitor; persons who have anatomic or functional asplenia; microbiologists who are routinely exposed to isolates of N. meningitidis; and persons identified to be at increased risk because of a meningococcal disease outbreak caused by serogroup B. ACIP recommends MenB booster doses for previously vaccinated persons who become or remain at increased risk. In addition, ACIP recommends a MenB series for adolescents and young adults aged 16-23 years on the basis of shared clinical decision-making to provide short-term protection against disease caused by most strains of serogroup B N. meningitidis.

Invasive Meningococcal Disease due to Nongroupable Neisseria meningitidis-Active Bacterial Core Surveillance Sites, 2011-2016.

We characterized 22 meningococcal disease cases due to nongroupable Neisseria meningitidis, a rare cause of invasive disease. Disease presentation and severity were similar to those for serogroupable meningococcal disease. However, 7 (32%) patients had complement deficiency or abnormal complement testing results, highlighting the importance of complement testing for nongroupable cases.

University-Based Outbreaks of Meningococcal Disease Caused by Serogroup B, United States, 2013-2018.

We reviewed university-based outbreaks of meningococcal disease caused by serogroup B and vaccination responses in the United States in the years following serogroup B meningococcal (MenB) vaccine availability. Ten university-based outbreaks occurred in 7 states during 2013-2018, causing a total of 39 cases and 2 deaths. Outbreaks occurred at universities with 3,600-35,000 undergraduates. Outbreak case counts ranged from 2 to 9 cases; outbreak duration ranged from 0 to 376 days. All 10 universities implemented MenB vaccination: 3 primarily used MenB-FHbp and 7 used MenB-4C. Estimated first-dose vaccination coverage ranged from 14% to 98%. In 5 outbreaks, additional cases occurred 6-259 days following MenB vaccination initiation. Although it is difficult to predict outbreak trajectories and evaluate the effects of public health response measures, achieving high MenB vaccination coverage is crucial to help protect at-risk persons during outbreaks of meningococcal disease caused by this serogroup.

Meningococcal Disease Among College-Aged Young Adults: 2014-2016.

: media-1vid110.1542/5839998266001PEDS-VA_2018-2130Video Abstract BACKGROUND: Freshman college students living in residence halls have previously been identified as being at an increased risk for meningococcal disease. In this evaluation, we assess the incidence and characteristics of meningococcal disease in college-aged young adults in the United States. METHODS: The incidence and relative risk (RR) of meningococcal disease among college students compared with noncollege students aged 18 to 24 years during 2014-2016 were calculated by using data from the National Notifiable Diseases Surveillance System and enhanced meningococcal disease surveillance. Differences in demographic characteristics and clinical features of meningococcal disease cases were assessed. Available meningococcal isolates were characterized by using slide agglutination, polymerase chain reaction, and whole genome sequencing. RESULTS: From 2014 to 2016, 166 cases of meningococcal disease occurred in persons aged 18 to 24 years, with an average annual incidence of 0.17 cases per 100 000 population. Six serogroup B outbreaks were identified on college campuses, accounting for 31.7% of serogroup B cases in college students during this period. The RR of serogroup B meningococcal (MenB) disease in college students versus noncollege students was 3.54 (95% confidence interval: 2.21-5.41), and the RR of serogroups C, W, and Y combined was 0.56 (95% confidence interval: 0.27-1.14). The most common serogroup B clonal complexes identified were CC32/ET-5 and CC41/44 lineage 3. CONCLUSIONS: Although the incidence is low, among 18- to 24-year-olds, college students are at an increased risk for sporadic and outbreak-associated MenB disease. Providers, college students, and parents should be aware of the availability of MenB vaccines.

Epidemiology of Meningococcal Disease Outbreaks in the United States, 2009-2013.

Background: Although the incidence of meningococcal disease is low in the United States, outbreaks remain a serious public health concern. In this evaluation, we identify and describe outbreaks of meningococcal disease. Methods: A retrospective review of all meningococcal disease cases reported from 1 January 2009 to 31 December 2013 was performed by state health departments and the Centers for Disease Control and Prevention to identify meningococcal disease outbreaks. An outbreak was defined as ≥2 primary cases of the same serogroup within <3 months in an organization, or a ≥2-fold increase in disease rates in a community. Results: From 2009 to 2013, a total of 3686 cases of meningococcal disease were reported in the United States. Among these, 180 primary cases (4.9%) occurred as part of 36 outbreaks (17 organization-based and 19 community-based). Serogroup B accounted for 8 (47.1%) of the organization-based outbreaks, including 6 of 8 university outbreaks. Serogroup C accounted for 10 (52.6%) of the community-based outbreaks, including both of 2 outbreaks identified among men who have sex with men. Organization- and community-based outbreaks differed in predominant serogroup, age distribution of cases, and clinical syndrome. Among 33 outbreaks with known information, a vaccination and/or expanded chemoprophylaxis campaign was conducted in 16 (48.5%). Conclusions: Outbreak-associated cases account for approximately 5% of all meningococcal disease cases in the United States. Serogroup B is the primary cause of organization-based outbreaks, with the majority of university outbreaks due to serogroup B, and serogroup C is the primary cause of community-based outbreaks.

Review of the economic evidence presented to the United States Advisory Committee on Immunization Practices, 2012-2016.

We identified 16 Advisory Committee on Immunization Practices (ACIP) presentations from 2012 to 2016 that indicated 'cost' or 'economic' content. Characteristics were reviewed, abstracted, and tabulated to quantify and assess the transparency and consistency of economic evidence presented to ACIP. To assess transparency, we documented if each study identified author affiliation, conflicts of interest, study limitations, a clearly described model structure and other model attributes. To assess consistency, we identified the frequency of specific modeling choices, including the perspective, types of health outcomes considered, inclusion of specific types of costs, discount rate, and use of sensitivity analyses. Our results indicate that the content in these presentations appear to be transparent overall and consistent in several important areas, such as study perspective and health outcomes. However, we find the inclusion of particular types of direct costs, indirect costs, program costs, and sensitivity analyses are areas that could improve consistency.

Whole genome sequencing for investigations of meningococcal outbreaks in the United States: a retrospective analysis.

Although rare in the U.S., outbreaks due to Neisseria meningitidis do occur. Rapid, early outbreak detection is important for timely public health response. In this study, we characterized U.S. meningococcal isolates (N = 201) from 15 epidemiologically defined outbreaks (2009-2015) along with temporally and geographically matched sporadic isolates using multilocus sequence typing, pulsed-field gel electrophoresis (PFGE), and six whole genome sequencing (WGS) based methods. Recombination-corrected maximum likelihood (ML) and Bayesian phylogenies were reconstructed to identify genetically related outbreak isolates. All WGS analysis methods showed high degree of agreement and distinguished isolates with similar or indistinguishable PFGE patterns, or the same strain genotype. Ten outbreaks were caused by a single strain; 5 were due to multiple strains. Five sporadic isolates were phylogenetically related to 2 outbreaks. Analysis of 9 outbreaks using timed phylogenies identified the possible origin and estimated the approximate time that the most recent common ancestor emerged for outbreaks analyzed. U.S. meningococcal outbreaks were caused by single- or multiple-strain introduction, with organizational outbreaks mainly caused by a clonal strain and community outbreaks by divergent strains. WGS can infer linkage of meningococcal cases when epidemiological links are uncertain. Accurate identification of outbreak-associated cases requires both WGS typing and epidemiological data.

Meningococcal Disease Surveillance in Men Who Have Sex with Men - United States, 2015-2016.

Meningococcal disease is a rare, but serious, bacterial infection that progresses rapidly and can be life-threatening, even with prompt antibiotic treatment. Men who have sex with men (MSM) have previously been reported to be at increased risk for meningococcal disease compared with other men, and recent outbreaks of serogroup C meningococcal disease among MSM have occurred (1). However, the epidemiology of meningococcal disease among MSM in the United States is not well described, in part, because information about MSM has not historically been collected as part of routine meningococcal disease surveillance. To better characterize and identify risk factors for meningococcal disease in general, supplementary data and isolates have been collected since 2015 through enhanced meningococcal disease surveillance activities. During 2015-2016, 271 cases of meningococcal disease in men aged ≥18 years were reported to the National Notifiable Diseases Surveillance System (NNDSS) in 45 states participating in this enhanced surveillance. Forty-eight (17.7%) cases were in men identified as MSM, including 17 (37.8%) with human immunodeficiency virus (HIV) infection. Among MSM, 39 (84.8%) cases were caused by Neisseria meningitidis serogroup C, whereas this serogroup was responsible for only 16.4% of cases among men who were not known to be MSM (non-MSM). Despite improvements in surveillance, MSM likely remain underascertained among men with meningococcal disease. Improved surveillance data are needed to understand the prevalence of and risk for meningococcal disease among MSM and inform policy and prevention strategies. Vaccination with quadrivalent meningococcal conjugate (MenACWY) vaccine is recommended for the control of meningococcal disease outbreaks caused by serogroups A, C, W, or Y, including during outbreaks among MSM; in addition, all persons aged ≥2 months with HIV infection should receive MenACWY vaccine because of the increased risk for meningococcal disease.

Emergence of Localized Serogroup W Meningococcal Disease in the United States - Georgia, 2006-2016.

Several countries in Europe and Australia are reporting an increasing incidence of Neisseria meningitidis serogroup W (NmW) as a consequence of the rapid expansion of a single NmW clone belonging to clonal complex 11 (1-5). Because this clone is reported to be associated with more severe disease, unusual clinical presentations, and a high case fatality ratio (CFR), it is considered a hypervirulent strain (1,6). In the United States, NmW accounts for approximately 5% of meningococcal disease reported each year, and this proportion has remained stable for several years (7). However, localized increases in NmW have been reported, most notably in Florida during 2008-2009 (8). In Georgia, NmW accounted for only 3% of meningococcal disease cases reported during 2006-2013; however, between January 2014 and December 2016, 42% of all reported cases were NmW. Surveillance data from Georgia were analyzed to describe the epidemiology and clinical characteristics of NmW cases, and whole-genome sequencing of NmW isolates was performed for comparison with NmW strains circulating in the United States and worldwide. These data indicate that the U.S. NmW strains might have evolved from the same ancestor as the hypervirulent strain that is circulating globally. Genetic analysis demonstrates that these strains are closely related, which would suggest that genetic variation led to the rise of different strains from the same ancestor. Given the recent global expansion of this potentially hypervirulent NmW lineage, clinicians and public health officials need to remain vigilant in obtaining isolates to monitor changes in circulating strains.

Adoption of Serogroup B Meningococcal Vaccine Recommendations.

: media-1vid110.1542/5799875076001PEDS-VA_2018-0344Video Abstract BACKGROUND AND OBJECTIVES: In 2015, the Advisory Committee on Immunization Practices recommended that 16- to 23-year-olds may be vaccinated with the serogroup B meningococcal (MenB) vaccine on the basis of individual clinical decision-making (Category B). We assessed the following among US pediatricians and family physicians (FPs): (1) practices regarding MenB vaccine delivery, (2) factors influencing a decision to recommend the MenB vaccine, and (3) factors associated with discussing the MenB vaccine. METHODS: We surveyed a nationally representative sample of pediatricians and FPs via e-mail and Internet from October 2016 to December 2016. RESULTS: The response rate was 72% (660 of 916). During routine visits, 51% of pediatricians and 31% of FPs reported always or often discussing MenB vaccine. Among those who discussed often or always, 91% recommended vaccination; among those who never or rarely discussed, 11% recommended. We found that 73% of pediatricians and 41% of FPs currently administered the MenB vaccine. Although many providers reported not knowing about factors influencing recommendation decisions, MenB disease outbreaks (89%), disease incidence (62%), and effectiveness (52%), safety (48%), and duration of protection of MenB vaccine (39%) increased the likelihood of recommendation, whereas the Category B recommendation (45%) decreased likelihood. Those somewhat or not at all aware of the MenB vaccine (risk ratio 0.32 [95% confidence interval 0.25-0.41]) and those practicing in a health maintenance organization (0.39 [0.18-0.87]) were less likely, whereas those aware of disease outbreaks in their state (1.25 [1.08-1.45]) were more likely to discuss MenB vaccine. CONCLUSIONS: Primary care physicians have significant gaps in knowledge about MenB disease and the MenB vaccine, and this appears to be a major driver of the decision not to discuss the vaccines.

Fatal Nongroupable Neisseria meningitidis Disease in Vaccinated Patient Receiving Eculizumab.

Patients receiving eculizumab have an increased risk for meningococcal disease, but most reported cases are attributable to encapsulated meningococcal strains. We describe a case in which a nongroupable meningococcal strain, which rarely causes disease in healthy persons, caused fatal disease in an eculizumab recipient despite meningococcal vaccination.

Population structure of invasive Neisseria meningitidis in the United States, 2011-15.

OBJECTIVES: Meningococcal conjugate vaccines (MenACWY) were licensed in the United States in 2005. We assessed the population structure of invasive Neisseria meningitidis (Nm) ten years after recommended use of MenACWY among adolescents. METHODS: Meningococcal isolates obtained through Active Bacterial Core surveillance (ABCs) from 2000-05, 2006-10, and 2011-15 underwent whole genome or Sanger sequencing. Genome phylogenies were completed using maximum likelihood methods; and distribution of multilocus sequence typing (MLST) sequence type (ST) and clonal complex (CC), and PorA and FetA types were assessed. RESULTS: Prevalent serogroups (B, C, Y and W), CCs, and PorA and FetA types were detected in all three time periods, but dynamic changes were observed. The proportion of serogroup W CC11 isolates increased in 2011-15 and were most related to South American strains. Changes in CC distribution were also observed in serogroup C and serogroup Y. Phylogenetic analysis showed that U.S. serogroup W CC11s are closely related to a subset of U.S. serogroup C isolates; combined global analysis demonstrated that some CCs, including CC11, exhibit regional clustering. CONCLUSIONS: Overall, the Nm population structure has remained stable after MenACWY introduction. Dynamic changes in genotypes, unlikely related to vaccination, also occurred, highlighting the need for continued whole genome-based surveillance.