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HK J Paediatr (New Series)
Vol 6. No. 2, 2001
HK J Paediatr (New Series) 2001;6:131

Proceedings of The First Current Topic in Infectious Diseases

Serotype Distribution of Invasive and Noninvasive Strains of Pneumococci in Hong Kong

PL Ho

HK J Paediatr (new series) 2001;6:127-132

Proceedings of The First Current Topic in Infectious Diseases: Consensus Meeting on Conjugate Vaccines of the Center of Infection
Faculty of Medicine, The University of Hong Kong (Selected Abstracts)

The capsular polysaccharide is a major virulence factor in the pathogenesis of invasive pneumococcal disease. On the basis of the capsular specificity, the pneumococci can be grouped into about 90 serogroups and serotypes (SGTs). While much is known about the SGT distribution of S. pneumoniae isolates in the Western countries, the situation in Asian countries is unclear.16 To determine the coverage of the 7-valent conjugate vaccine for invasive and noninvasive isolates in Hong Kong, the capsular SGT of 721 nonduplicate isolates of S. pneumoniae from diverse sources were determined by the Quellung method.15 Of the 721 isolates, 383 isolates were obtained from the nasopharynx (NP) of children age between two to six years, attending day care centers or kindergartens during a territory-wide surveillance in 2000, 140 isolates were obtained from respiratory tract specimens of hospitalized patients in seven hospitals in 1998, and 199 isolates were obtained from blood (187) or CSF (12) of patients hospitalized in four hospitals between 1996 to 2000. SGT included in the 7-valent pneumococcal conjugate vaccine were 4, 6B, 9V, 14, 18C, 19F and 23F. At all age groups, the most common serotypes were 6B, 19F and 23F. Of the isolates from young children, the 7-valent conjugate vaccine respectively covered 65%, 88% and 88% of the NP, respiratory and invasive isolates. Our data showed that distribution of SGT among invasive and noninvasive isolates among young children in Hong Kong is similar to those reported in the United States. On the basis of the SGT distribution, the recent 7-valent pneumococcal conjugate vaccine could offer protection against many of the invasive pneumococcal infections among children in this locality.

Method and Process of Consensus Building

The consensus meeting on Consensus meeting on conjugate vaccines was held on February 17, 2001, as the first current topic in infectious diseases that was organized by the Centre of Infection, the University of Hong Kong. A panel of experts from the fields of Internal Medicine, Clinical Microbiology, Internal Medicine, Paediatrics and Public Health were provided with the latest scientific papers1-8 and were invited to speak and discuss on various aspects concerning the topic.

After the formal presentation, panel discussion was held. All speakers, invited discussants from various aspects of the medical fields and audiences actively participated in the discussion with further elaboration on issues around S. pneumoniae and H. influenzae disease burden, antimicrobial resistance and conjugate vaccine.

Finally, conclusions were drawn on the basis of the current scientific information and views expressed by the panel and other participants. Drafts in progress and final copies of the manuscript were distributed to panel for comments before submission for publication.

Consensus Panel Members

Daniel CS Chiu, Pediatrician in private practice
Susan SS Chiu, Assistant Professor, Department of Paediatrics, The University of Hong Kong
CB Chow, Consultant, Department of Paediatrics, Princess Margaret Hospital
PL Ho, Associate Professor, Department of Microbiology, The University of Hong Kong
YL Lau, Chair Professor in Paediatrics, Department of Paediatrics, The University of Hong Kong
CW Leung, Consultant, Department of Paediatrics, Princess Margaret Hospital
Dominic NC Tsang, Consultant, Department of Clinical Pathology, Queen Elizabeth Hospital
Kenneth WT Tsang, Associate Professor, Department of Medicine, University of Hong Kong.
Thomas HF Tsang, Community Physician, Department of Health
Samson SY Wong, Assistant Professor, Department of Microbiology, University of Hong Kong.
YH Yang, Professor, Beijing Children's Hospital, Beijing
KY Yuen, Chair Professor in Infectious Diseases, Department of Microbiology, The University of Hong Kong

Consensus Statements

Disease burden of paediatric Haemophilus influenzae type b infections in Hong Kong

1. The incidence of Haemophilus influenzae type b (Hib) diseases in Hong Kong appears to be low. Multiple confounding factors, such as prior antibiotic usage, might be the causes for the apparent low recorded prevalence.

2. Further study to collect epidemiological data in Hong Kong would be difficult due to the following factors:

a) Some children might have been given Hib vaccination on an individual basis.

b) There are quite a number of patients taking antibiotics prior to collection of specimens for cultures and the recovery rate of any microorganisms in these situations is relatively low.

3. Gaps in existing data should be addressed in future studies using new research methodology, such as the WHO rapid assessment tool.

Use of conjugate Haemophilus influenzae type b vaccine

1. Conjugate Hib vaccine has proven safety and efficacy in prevention of invasive Hib disease.

2. Thorough cost-effective/benefit/utility analysis and comparison of existing program would be very helpful in supporting recommendation for universal vaccination in this locality. Broader discussion/consultation on what constitute the "acceptable" cost is required.

Disease burden of pneumococcal infections in Hong Kong

1. Disease burden of pneumococcal disease is still unclear and further study would be needed for different at-risk groups.

2. Penicillin-resistant and multiple antibiotic-resistant pneumococci are a major problem in Hong Kong.

Use of conjugate pneumococcal vaccine

1. The heptavalent conjugate vaccine provides good coverage of the serotypes causing invasive pneumococcal disease in Hong Kong at present.

2. Conjugate pneumococcal vaccine is effective in decreasing vaccine strain carriage, and preventing invasive pneumococcal disease in young children from published experience.

Acknowledgement

The meeting was sponsored by the Hong Kong Paediatric Foundation.

References

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2. Lau YL, Yung R, Low L, Sung R, Leung CW, Lee WH. Haemophilus influenzae type b infections in Hong Kong. Pediatr Infect Dis J 1998;17:S165-S169.

3. Lau YL. Haemophilus influenzae type b diseases in Asia. Bull.World Health Organ 1999;77:867-8.

4. Levine OS, Schwartz B, Pierce N, Kane M. Development, evaluation and implementation of Haemophilusinfluenzae type b vaccines for young children in developing countries: current status and priority actions. Pediatr Infect Dis J 1998;17:S95-S113.

5. Heath PT. Haemophilus influenzae type b conjugate vaccines: a review of efficacy data. Pediatr Infect Dis J 1998;17:S117-S122.

6. American Academy of Pediatrics. American Academy of Pediatrics. Committee on Infectious Diseases. Policy statement: recommendations for the prevention of pneumococcal infections, including the use of pneumococcal conjugate vaccine (Prevnar), pneumococcal polysaccharide vaccine, and antibiotic prophylaxis. Pediatrics 2000;106: 362-6.

7. Hausdorff WP, Bryant J, Kloek C, Paradiso PR, Siber GR. The contribution of specific pneumococcal serogroups to different disease manifestations: implications for conjugate vaccine formulation and use, part II. Clin Infect Dis 2000;30:122-40.

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11. Yang Y, Shen X, Vuori-Holopainen E, et al. Sero-etiology of acute lower respiratory infections among hospitalized children in Beijing. Pediatr Infect Dis J 2001;20:52-8.

12. Lau YL, Low LC, Yung R, et al. Invasive Haemophilus influenzae type b infections in children hospitalized in Hong Kong, 1986-1990. Hong Kong Hib Study Group. Acta Paediatr 1995;84:173-6.

13. Sung RY, Cheng AF, Chan RC, Tam JS, Oppenheimer SJ. Epidemiology and etiology of pneumonia in children in Hong Kong. Clin Infect Dis 1993;17:894-6.

14. Ho PL, Que TL, Tsang DN, Ng TK, Chow KH, Seto WH. Emergence of fluoroquinolone resistance among multiply resistant strains of Streptococcus pneumoniae in Hong Kong. Antimicrob. Agents Chemother 1999;43:1310-3.

15. Ho PL, Yam WC, Cheung TKM, et al. Rapid rise of fluoroquinolone resistance among Streptococcus pneumoniae in Hong Kong linked to acquisition of fluoroquinolone resistance by the locally dominant Spanish 23F clone. Emerg Infect Dis 2001. In press.

16. Luey KY, Kam KM. Vaccine coverage of Streptococcus pneumoniae in Hong Kong with attention to the multiple-antibiotic-resistant strains. Vaccine 1996;14:1573-80.

 
 

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