We assessed the impact of pneumococcal conjugate vaccines on pneumococcal otitis media (OM) among children living in Navajo and White Mountain Apache Tribal lands. During the PCV7 era (2000-2009), the proportion of vaccine-type OM declined. However, vaccine-type OM (predominantly 3, 19A, and 19F) persisted in the PCV13 era (2010-2019).

American Indian (AI) communities in the Southwest have a high burden of invasive pneumococcal disease (IPD) and COVID-19. Through laboratory-based surveillance, the impact of the pandemic on IPD incidence and serotype distribution was evaluated in two AI communities. IPD rates were lower during the pandemic (21.8 vs. 39.0/100 000 pre-pandemic). Rates increased in 2021 compared to 2020 but not to pre-pandemic levels. Cases with SARS-CoV-2 co-infection had a higher case fatality rate (45.2% vs. 17.6% without co-infection). No significant change in serotype distribution was observed. Continued surveillance in these communities is critical to understand the changing IPD burden as the pandemic evolves.

We describe the epidemiology of invasive group B streptococcal (GBS) disease among non-pregnant Alaska adults using statewide surveillance data. During 2004-2023, 880 cases of invasive GBS disease were reported for an age-adjusted annual incidence of 9.1 (95% CI, 8.5-9.7) cases per 100,000 adults. Incidence increased 1.9-fold (95% CI, 1.6-2.2) between 2004-2013 and 2014-2023. Adults aged ≥65 years had a 4.4-fold higher risk of invasive disease compared to younger adults, and 47% of adults with invasive GBS had diabetes. Healthcare providers should be aware of populations at increased risk, potentially allowing for more prompt treatment.

BACKGROUND: Widespread use of pneumococcal conjugate vaccines (PCVs) has reduced vaccine-type invasive pneumococcal disease (IPD). We describe the serotype distribution of IPD after extensive use of ten-valent PCV (PCV10; Synflorix, GSK) and 13-valent PCV (PCV13; Prevenar 13, Pfizer) globally. METHODS: IPD data were obtained from surveillance sites participating in the WHO-commissioned Pneumococcal Serotype Replacement and Distribution Estimation (PSERENADE) project that exclusively used PCV10 or PCV13 (hereafter PCV10 and PCV13 sites, respectively) in their national immunisation programmes and had primary series uptake of at least 70%. Serotype distribution was estimated for IPD cases occurring 5 years or more after PCV10 or PCV13 introduction (ie, the mature period when the serotype distribution had stabilised) using multinomial Dirichlet regression, stratified by PCV product and age group (<5 years, 5-17 years, 18-49 years, and ≥50 years). FINDINGS: The analysis included cases occurring primarily between 2015 and 2018 from 42 PCV13 sites (63 362 cases) and 12 PCV10 sites (6806 cases) in 41 countries. Sites were mostly high income (36 [67%] of 54) and used three-dose or four-dose booster schedules (44 [81%]). At PCV10 sites, PCV10 serotypes caused 10·0% (95% CI 6·3-12·9) of IPD cases in children younger than 5 years and 15·5% (13·4-19·3) of cases in adults aged 50 years or older, while PCV13 serotypes caused 52·1% (49·2-65·4) and 45·6% (40·0-50·0), respectively. At PCV13 sites, PCV13 serotypes caused 26·4% (21·3-30·0) of IPD cases in children younger than 5 years and 29·5% (27·5-33·0) of cases in adults aged 50 years or older. The leading serotype at PCV10 sites was 19A in children younger than 5 years (30·6% [95% CI 18·2-43·1]) and adults aged 50 years or older (14·8% [11·9-17·8]). Serotype 3 was a top-ranked serotype, causing about 9% of cases in children younger than 5 years and 14% in adults aged 50 years or older at both PCV10 and PCV13 sites. Across all age and PCV10 or PCV13 strata, the proportion of IPD targeted by higher-valency PCVs beyond PCV13 was 4·1-9·7% for PCV15, 13·5-36·0% for PCV20, 29·9-53·8% for PCV21, 15·6-42·0% for PCV24, and 31·5-50·1% for PCV25. All top-ten ranked non-PCV13 serotypes are included in at least one higher-valency PCV. INTERPRETATION: The proportion of IPD due to serotypes included in PCVs in use was low in mature PCV10 and PCV13 settings. Serotype distribution differed between PCV10 and PCV13 sites and age groups. Higher-valency PCVs target most remaining IPD and are expected to extend impact. FUNDING: Bill & Melinda Gates Foundation as part of the WHO Pneumococcal Vaccines Technical Coordination Project.

Background. Despite use of highly effective conjugate vaccines, invasive pneumococcal disease (IPD) remains a leading cause of morbidity and mortality and disproportionately affects Indigenous populations. Although included in the 13-valent pneumococcal conjugate vaccine (PCV13), which was introduced in 2010, serotype 3 continues to cause disease among Indigenous communities in the Southwest USA. In the Navajo Nation, serotype 3 IPD incidence increased among adults (3.8/100 000 in 2001-2009 and 6.2/100 000 in 2011-2019); in children the disease persisted although the rates dropped from 5.8/100 000 to 2.3/100 000.Methods. We analysed the genomic epidemiology of serotype 3 isolates collected from 129 adults and 63 children with pneumococcal carriage (n=61) or IPD (n=131) from 2001 to 2018 of the Navajo Nation. Using whole-genome sequencing data, we determined clade membership and assessed changes in serotype 3 population structure over time.Results. The serotype 3 population structure was characterized by three dominant subpopulations: clade II (n=90, 46.9 %) and clade Iα (n=59, 30.7 %), which fall into Clonal Complex (CC) 180, and a non-CC180 clade (n=43, 22.4 %). The proportion of clade II-associated IPD cases increased significantly from 2001 to 2010 to 2011-2018 among adults (23.1-71.8 %; P<0.001) but not in children (27.3-33.3 %; P=0.84). Over the same period, the proportion of clade II-associated carriage increased; this was statistically significant among children (23.3-52.6 %; P=0.04) but not adults (0-50.0 %, P=0.08).Conclusions. In this setting with persistent serotype 3 IPD and carriage, clade II has increased since 2010. Genomic changes may be contributing to the observed trends in serotype 3 carriage and disease over time.

Here we describe the relationships between serotypes, genotypes, and antimicrobial susceptibility among isolates causing invasive pneumococcal disease in Alaskan children during the pneumococcal conjugate vaccine (PCV) era. From 2001 to 2013 we received 271 isolates representing 33 serotypes. The most common serotypes were 19A (29.5%, n= 80), 7F (12.5%, n= 34), 15B/C (6.3%, n= 17), and 22F (4.8%, n= 13). Multilocus sequence typing identified 11 clonal complexes (CC) and 45 singletons. Five CCs accounted for 52% (141/271) of the total: CC199 (21% [n= 57], serotypes 19A, 15B/C), CC191 (12.2% [n= 33], serotype 7F), CC172 (10.3% [n= 28], serotypes 19A, 23A, 23B), CC433 (4.4% [n= 12], serotype 22F), and CC100 (4.4% [n= 12], serotype 33F). The proportion of isolates nonsusceptible to erythromycin and tetracycline increased after 13-valent PCV use (14% [n= 30] versus 29% [n= 14]; P= 0.010) and (4% [n= 9] versus 22% [n= 11]; P< 0.001), respectively. The genetic diversity also increased after 13-valent PCV use (Simpson's diversity index =0.95 versus 0.91; P= 0.022).

The rapid emergence of antibiotic-resistant pneumococcal strains has reduced treatment options. The aim of this study was to determine antimicrobial susceptibilities, serotype distributions, and molecular resistance mechanisms among macrolide-resistant invasive pneumococcal isolates in Alaska from 1986 to 2010. We identified cases of invasive pneumococcal disease in Alaska from 1986 to 2010 through statewide population-based laboratory surveillance. All invasive pneumococcal isolates submitted to the Arctic Investigations Program laboratory were confirmed by standard microbiological methods and serotyped by slide agglutination and the Quellung reaction. MICs were determined by the broth microdilution method, and macrolide-resistant genotypes were determined by multiplex PCR. Among 2,923 invasive pneumococcal isolates recovered from 1986 to 2010, 270 (9.2%) were nonsusceptible to erythromycin; 177 (66%) erythromycin-nonsusceptible isolates demonstrated coresistance to penicillin, and 167 (62%) were multidrug resistant. The most frequent serotypes among the macrolide-resistant isolates were serotypes 6B (23.3%), 14 (20.7%), 19A (16.7%), 9V (8.9%), 19F (6.3%), 6A (5.6%), and 23F (4.8%). mef and erm(B) genes were detected in 207 (77%) and 32 (12%) of the isolates, respectively. Nineteen (7%) of the erythromycin-nonsusceptible isolates contained both mef and erm(B) genotypes; 15 were of serotype 19A. There was significant year-to-year variation in the proportion of isolates that were nonsusceptible to erythromycin (P < 0.001). Macrolide resistance among pneumococcal isolates from Alaska is mediated predominantly by mef genes, and this has not changed significantly over time. However, there was a statistically significant increase in the proportion of isolates that possess both erm(B) and mef, primarily due to serotype 19A isolates.

We investigated serotype 6A/6C invasive pneumococcal disease (IPD) incidence, genetic diversity, and carriage before and after 7-valent pneumococcal conjugate vaccine (PCV7) introduction in Alaska. IPD cases (1986-2009) were identified through population-based laboratory surveillance. Isolates were initially serotyped by conventional methods, and 6C isolates were differentiated from 6A by polymerase chain reaction. Among invasive and carriage isolates initially typed as 6A, 35% and 50% were identified as 6C, respectively. IPD rates caused by serotype 6A or 6C among children <5 years did not change from the pre- to post-PCV7 period (P = 0.71 and P = 0.09, respectively). Multilocus sequence typing of IPD isolates revealed 28 sequence types. The proportion of serotype 6A carriage isolates decreased from 7.4% pre-PCV7 to 1.8% (P < 0.001) during 2008-2009; the proportion of serotype 6C carriage isolates increased from 3.0% to 8.4% (P = 0.004) among children <5 years. Continued surveillance is warranted to monitor changes in serotype distribution and prevalence.

We evaluated nasopharyngeal carriage of Streptococcus pneumoniae (pneumococci) in nine Alaskan communities and used an algorithm combining microbiologic, serologic, and sequential multiplex PCR (MP-PCR) techniques to serotype the isolates. After microbiological identification as pneumococci, isolates (n = 1,135) were serotyped using latex agglutination and Quellung tests (LA/Q) as well as a series of six sequential MP-PCR assays. Results from the two methods agreed for 94% (1,064/1,135) of samples. Eighty-six percent (61/71) of the discordant results were resolved. Discordant results occurred because (i) the MP-PCR gel was misread (31/61 [51%]), (ii) the LA/Q agglutination was misinterpreted (13/61 [21%]), (iii) two serotypes or sets of serotypes were identified by MP-PCR and only one of the two was identified by LA/Q (9/61 [15%]), (iv) different serotypes or sets of serotypes were identified by LA/Q and MP-PCR and both were correct (7/61 [11%]), and (v) the capsular polysaccharide locus (cps) did not amplify during the initial MP-PCR but was present upon retesting (1/61 [2%]). Overall, isolation of pneumococci followed by MP-PCR quickly and accurately identified pneumococcal serotypes in >97% of samples and made available isolates for additional tests such as antimicrobial susceptibility. Misinterpretation of the MP-PCR gel was identified as the main source of discordance. Increasing the number of MP-PCRs from six to seven and reducing the number of serotypes in each reaction may reduce this error. This method may be of use to laboratories characterizing large numbers of S. pneumoniae samples, especially when antimicrobial susceptibility data are needed.