Changes in the Distribution of Capsular Serotypes of Streptococcus pneumoniae Isolated from Adult Respiratory Specimens in Japan

Strategies for pneumococcal vaccination in older adults in the coming era

Pneumonia, predominantly caused by Streptococcus pneumoniae, remains a leading cause of global mortality. The 23-valent Pneumococcal polysaccharide vaccine (PPSV23) and conjugate vaccines (PCVs) are vital measures to fight against it. This paper discussed the changes in pneumococcal vaccination strategies, particularly for older adults, as vaccine effectiveness and epidemiological patterns shift. While PPSV23 maintains effectiveness against invasive pneumococcal disease (IPD), its effectiveness against pneumococcal pneumonia is declining. Conversely, PCV13 consistently demonstrates effectiveness against both IPD and pneumonia. Consequently, the US Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommends using PCVs, notably PCV20 and PCV15, over PPSV23. Japanese studies indicate a change in the efficacy/effectiveness of PPSV23 following PCV introduction in children, likely owing to serotype replacement and herd immunity. Additionally, recent data reveals a plateau in the reduction of PCV13 and PPSV23-covered serotypes, posing a challenge to current strategies. This paper indicates a paradigm shift in pneumonia management, acknowledging its chronic nature and potential to exacerbate other diseases. The future of pneumococcal vaccination lies in broader serotype coverage through PCVs, adapting to serotype changes driven by childhood vaccination programs. Furthermore, continuous research and vaccine development are crucial in this evolving field.

Effects of PCV10 and PCV13 on pneumococcal serotype 6C disease, carriage, and antimicrobial resistance

BACKGROUND

The cross-protection of pneumococcal conjugate vaccines (PCV) against serotype 6C is not clearly documented, although 6C represents a substantial burden of pneumococcal disease in recent years. A systematic review by the World Health Organization that covered studies through 2016 concluded that available data were insufficient to determine if either PCV10 (which contains serotype 6B but not 6A) or PCV13 (containing serotype 6A and 6B) conferred protection against 6C.

METHODS

We performed a systematic review of randomized controlled trials and observational studies published between January 2010 - August 2022 (Medline/Embase), covering the direct, indirect, and overall effect of PCV10 and PCV13 against 6C invasive pneumococcal disease (IPD), non-IPD, nasopharyngeal carriage (NPC), and antimicrobial resistance (AMR).

RESULTS

Of 2548 publications identified, 112 were included. Direct vaccine effectiveness against 6C IPD in children ranged between 70 and 85 % for ≥ 1 dose PCV13 (n = 3 studies), was 94 % in fully PCV13 vaccinated children (n = 2), and -14 % for ≥ 1 dose of PCV10 (n = 1). Compared to PCV7, PCV13 efficacy against 6C NPC in children was 66 % (n = 1). Serotype 6C IPD rates or NPC prevalence declined post-PCV13 in most studies in children (n = 5/6) and almost half of studies in adults (n = 5/11), while it increased post-PCV10 for IPD and non-IPD in all studies (n = 6/6). Changes in AMR prevalence were inconsistent.

CONCLUSIONS

In contrast to PCV10, PCV13 vaccination consistently protected against 6C IPD and NPC in children, and provided some level of indirect protection to adults, supporting that serotype 6A but not 6B provides cross-protection to 6C. Vaccine policy makers and regulators should consider the effects of serotype 6A-containing PCVs against serotype 6C disease in their decisions.

Burden of illness associated with pneumococcal infections in Japan - a targeted literature review

INTRODUCTION

Pneumococcal diseases (PDs) are among the leading causes of mortality and morbidity worldwide. However, the evidence on epidemiology, health economic, and patient-reported outcomes has not been systematically reviewed and published in Japan. This study aimed to assess the burden, treatment adherence and compliance, and serotype distribution associated with PDs in Japan.

METHOD

One hundred and eight studies were identified between January 2005 and June 2020. The identified studies were mostly regional and with a limited scale, clinical settings, and populations.

RESULTS

In 2013-2017, invasive PD incidence rates were 4.98-9.47/100,000 in <4-year-olds, 0.36/100,000 in 5-14-year-olds, 0.46/100,000 in 15-64-year-olds, and 1.50-5.38/100,000 in the elderly. The incidence of invasive PDs in children decreased from 24.6/100,000 in 2008 to 10.7/100,000 in 2013 after the introduction of PCV7 and further declined to 10.3/100,000 in 2014 after PCV13 was introduced. From 2014, the prevalence of PCV13 serotypes decreased across all age groups along with a decrease of PPV23 serotypes, but an increase of PPV23 serotypes not included in PCV13 among adults and the elderly. No study reported health-related quality-of-life data for PDs. In children, direct costs were 340,905-405,978 JPY (3,099-3,691 USD) per pneumococcal bacteraemia, 767,447-848,255 JPY (6,977-7,711 USD) per pneumococcal meningitis, and 79,000 JPY (718 USD) per pneumococcal acute otitis media episodes. In adults and the elderly, the direct cost of pneumococcal pneumonia was 348,280-389,630 JPY (3,166-3,542 USD). The average hospital stay length was 7.2-31.9 days in children, 9.0 days in adults and 9.0-28.7 days in adults and the elderly.

CONCLUSIONS

The epidemiological burden of PDs remains high in Japan, especially among children and the elderly with invasive PDs accounting for a very small proportion of all PDs. A significant impact of the PCV13 vaccine program was reported, while the PPV23's impact remains unclear. A substantial decrease in quality-adjusted life years in adults and the elderly and a high economic burden may exist.

Cationic pullulan nanogel as a safe and effective nasal vaccine delivery system for respiratory infectious diseases

The mucosal surfaces of the respiratory and gastrointestinal tracts are continuously exposed to countless beneficial and pathologic antigens. These mucosal surfaces are thus equipped with an immune system that is unique from those elsewhere in the body; this unique system provides the first line of immune surveillance and defense against pathogen invasion. The sophisticated immune induction machinery in the aero–digestive tract involves mucosa-associated lymphoid tissues, including nasopharyngeal- and gut-associated lymphoid tissues, for the generation of antigen-specific humoral and cellular immune responses. Consequently, nasal or oral immunization with an appropriate vaccine delivery vehicle prompts the induction of protective immunity in both the mucosal and systemic compartments, leading to a double layer of protection against pathogens. To harness the benefits of mucosal vaccines, various mucosal antigen delivery vehicles are under development, and a cationic cholesteryl-group-bearing pullulan nanogel (cCHP nanogel) has emerged as a potent nasal vaccine delivery system for the induction of protective immunity against respiratory infections.

Serotype distribution of Streptococcus pneumoniae isolated from adult respiratory tract infections in nationwide Japanese surveillances from 2006 to 2014

BACKGROUND AND OBJECTIVE

Reports on the efficacy of pneumococcal conjugate vaccines (PCVs) have been received from many countries. However, in countries where the 7-valent PCV (PCV7) and 13-valent PCV (PCV13) were introduced, overall coverage of the serotypes by the vaccine gradually decreased due to pneumococcal serotype replacement. The aim of this study is to assess the distribution of pneumococcal serotypes and to also provide basic data on adult respiratory infection in Japan.

METHODS

We analyzed 1086 Streptococcus pneumoniae strains that had been isolated from respiratory tract infection specimens in adult patients from 2006 to 2014. Capsular typing was performed by the Quellung reaction and multiplex PCR.

RESULTS

Among all 1086 strains, serotype 3 was the most common and was identified in 160 strains (14.7%), followed by serotypes 19F, 6B, 19A and 23F. From 2006-10 to 2012-14, the coverage rate of PCV7 tended to gradually decrease. Particularly, serotypes 6B and 19F of penicillin non-susceptible strains decreased. On the other hand, serotypes 19A and 15A of penicillin non-susceptible strains increased. However, coverage by PCV13 of penicillin-resistant S. pneumoniae (PRSP) (penicillin G minimum inhibitory concentration ≥2 μg/mL) remained high (88.7% [2006-10], 88.0% [2012-14]).

CONCLUSIONS

In Japan, PCV13 vaccination of adults became available from June 2014. Our study demonstrated that most PRSP (88.0%) still remain covered by PCV13. At present, the introduction of PCV13 in adult clinical practice seems to be highly significant. However, there is a possibility that the distribution has been changing, and careful screening should be continued in the future.

Serotype Replacement in Adult Pneumococcal Pneumonia after the Introduction of Seven-Valent Pneumococcal Conjugate Vaccines for Children in Japan: a Systematic Literature Review and Pooled Data Analysis

Streptococcus pneumoniae is the major causative agent for adult pneumonia. Following the introduction of pneumococcal conjugate vaccines (PCV) for children, serotype replacement has been reported in adult invasive pneumococcal diseases but has not been well studied for cases of pneumococcal pneumonia in adults in Asia. To investigate serotype replacement in adult pneumococcal pneumonia in Japan, we conducted a systematic review of the literature across 5 databases using terms, including pneumococcus, serotype, their synonyms, and derivatives. After the assessment of the identified articles, data on the pneumococcal serotype distribution among adult pneumonia cases were extracted from relevant studies. Twenty-two studies were reviewed, and 4 relevant articles were included in the pooled data analysis. The proportion of the 7-valent PCV (PCV7)-covered serotypes from before and after the introduction of PCV7 for children (－18.1%, p ＜ 0.001) significantly decreased; moreover, the proportions of serotypes covered by PCV13 but not PCV7 (＋9.9%, p = 0.003) and those covered by the 23-valent polysaccharide vaccine but not PCV7 (＋9.4%, p = 0.007) significantly increased. Serotype replacement occurred in adult cases of pneumococcal pneumonia following vaccination of children with PCV7 in Japan. Further nationwide surveillance is warranted to investigate serotype replacement in the post-PCV13 phase.