Po Yen Chen

National survey of invasive pneumococcal diseases in Taiwan under partial PCV7 vaccination in 2007: emergence of serotype 19A with high invasive potential.

We conducted an active, population-based laboratory surveillance study to evaluate the epidemiologic features of invasive pneumococcal disease (IPD) in Taiwan. Concurrently, nasopharyngeal colonization of Streptococcus pneumoniae was evaluated among 1128 healthy children aged <or=5 years. The overall incidence was highest among children aged 2-4 years (15.6/100,000). Serotype 19A, which had never been reported in Taiwan previously, caused a substantial fraction of the invasive diseases (OR, 9.6; 95% CI, 3.1-29.4) among children aged 2-4 years. Comparing serotype distributions of the isolates from nasopharyngeal colonization among children aged <or=5 years, serotypes 14 (OR, 17.3; 95% CI, 5.2-57.9) and 19A (OR, 14.9; 95% CI, 1.9-117) had the highest invasive potential. The study found that serotype 19A expanded in Taiwan, a country with a low 7-valent conjugate pneumococcal vaccine coverage. The 7-valent conjugate pneumococcal vaccines covered 73% of cases in children aged between 2 and 4 years, and 64.7% of cases in children aged <2 years. Among patients aged >or=65 years, the 23-valent pneumococcal polysaccharide vaccine covered 70.4% of cases. In the future, a broader pneumococcal vaccine is needed.

Prevalence of Methicillin-Resistant Staphylococcus aureus Nasal Colonization among Taiwanese Children in 2005 and 2006

ABSTRACT From July 2005 to October 2006, a total of 3,046 children, of ages between 2 months and 5 years, presented for a well-child health care visit to one of three medical centers, which are located in the northern, central, and southern parts of Taiwan, and were surveyed for nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA). The overall prevalences of S. aureus and MRSA nasal carriage among the children were 23% and 7.3%, respectively (18% and 4.8% in the central region, 25% and 6.7% in the southern region, and 27% and 9.5% in the northern region). Of the 212 MRSA isolates (96%) available for analysis, a total of 10 pulsed-field gel electrophoresis (PFGE) patterns with two major patterns (C [61%] and D [28%]) were identified. One hundred forty-nine isolates (70%) contained type IV staphylococcal cassette chromosome mec (SCCmec) DNA, and 55 isolates (26%) contained SCCmec VT. The presence of Panton-Valentine Leukocidin (PVL) genes was detected in 60 isolates (28%). Most MRSA isolates belonged to one of two major clones, characterized as sequence type 59 (ST59)/PFGE C/SCCmec IV/absence of PVL genes (59%) and ST59/PFGE D/SCCmec VT/presence of PVL genes (25%). We concluded that between 2005 and 2006, 7.3% of healthy Taiwanese children were colonized by MRSA in nares. MRSA harbored in healthy children indicates an accelerated spread in the community.

Laboratory-based surveillance and molecular epidemiology of influenza virus in Taiwan.

ABSTRACT A laboratory-based surveillance network of 11 clinical virological laboratories for influenza viruses was established in Taiwan under the coordination of the Center for Disease Control and Prevention (CDC), Taiwan. From October 2000 to March 2004, 3,244 influenza viruses were isolated, including 1,969 influenza A and 1,275 influenza B viruses. The influenza infections usually occurred frequently in winter in the northern hemisphere. However, the influenza seasonality in Taiwan was not clear during the four seasons under investigation. For example, the influenza A viruses peaked during the winters of 2001, 2002, and 2003. However, some isolated peaks were also found in the summer and fall (June to November) of 2001 and 2002. An unusual peak of influenza B also occurred in the summer of 2002 (June to August). Phylogenetic analysis shows that influenza A isolates from the same year were often grouped together. However, influenza B isolates from the year 2002 clustered into different groups, and the data indicate that both B/Victoria/2/87-like and B/Yamagata/16/88-like lineages of influenza B viruses were cocirculating. Sequence comparison of epidemic strains versus vaccine strains shows that many vaccine-like Taiwanese strains were circulating at least 2 years before the vaccine strains were introduced. No clear seasonality of influenza reports in Taiwan occurred in contrast to other more continental regions.

Molecular epidemiology of clinical isolates of methicillin-resistant Staphylococcus aureus in Taiwan

ABSTRACT During July 2000 and October 2001, a total of 595 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were collected from six medical centers distributed in northern, central, and southern Taiwan. Specimen sources included blood (n = 279), pus (n = 173), sputum (n = 94), body fluids (n = 21), catheter tips (n = 20), and urine (n = 8). Pulsed-field gel electrophoresis (PFGE) with SmaI digestion was used to fingerprint these isolates. A total of 31 genotypes with 97 type-subtypes were identified. Subtypes could be identified in 7 genotypes. While there were 6 to 15 genotypes in each hospital, 433 isolates (73%) were shown to belong to a major type (genotype A, with 29 subtypes). This genotype was not only the type prevailing in all six hospitals but also the predominant clone in each hospital, accounting for 46 to 89% of all isolates in each hospital. Genotype C (16 subtypes) was the second dominant genotype, accounting for 9% of all isolates, and was distributed in five hospitals. Genotypes D (11 subtypes), E (5 subtypes), and B (6 subtypes) were distributed in five, four, and three hospitals, respectively. The other 26 types (30 type-subtypes) were minor. We conclude that the majority of MRSA clinical isolates shared a common PFGE pattern, indicating the presence of a single, epidemic MRSA clone prevailing in major hospitals in Taiwan.

Waning population immunity to measles in Taiwan

To evaluate the population immunity to measles in Taiwan where the coverage rate of the measles vaccine was >95% for more than a decade, anti-measles IgG was determined in 3552 Taiwanese volunteers in 2007. The overall seroprevalence was 74.7% (95% confidence interval [CI]: 73.3-76.1%). In subgroups aged 2-25 years, to whom at least 2 doses of measles-containing vaccine were given, there was a declining trend of seropositivity with age from 94.5% at 2 years to 50.6% at 21-25 years (p<0.0001). Age (odds ratio [OR]: 1.0464, 95% CI: 1.043-1.085) and male gender (OR: 1.466, 95% CI: 1.131-1.901) were independent factors predicting seronegative sera in this population. Seroprevalence was uniformly >95% in the older population (≥ 35 years) who had not been immunized against measles. The waning vaccine-induced immunity may have impact on the control of measles in the future, especially when the vaccinated population becomes older.

The impact of the heptavalent pneumococcal conjugate vaccine on risk factors for Streptococcus pneumoniae carriage in children.

Background: The aim of the study was to investigate whether the 7-valent pneumococcal conjugate vaccine (PCV7) alters common risk factors of nasopharyngeal carriage by Streptococcus pneumoniae in children. Methods: From July 2005 through December 2010, we performed a cross-sectional study investigating risk factors associated with pneumococcal carriage in children. Parents of participating children completed questionnaires including whether or not the children received PCV7 vaccination. Results: Among 9705 children, 20.2% of them received at least 1 dose of the PCV7 vaccine. Multivariate logistic regression models identified older age, having 1 sibling in a family, history of acute otitis media and household exposure to smoking as independent risk factors for pneumococcal carriage in the unvaccinated group, but not associated with pneumococcal carriage in the vaccinated group. The number of siblings ≥2 in a family, history of upper respiratory tract infection and child-care attendance were strong factors associated with pneumococcal carriage in children, regardless of vaccination. In vaccinated group, breast-feeding was associated with increased nonvaccine type pneumococcal carriage, mainly in children with upper respiratory tract infection. Conclusions: PCV7 decreased the association between pneumococcal carriage and older age, 1 sibling in a family, history of acute otitis media and household exposure to smoking, but increased the association between pneumococcal carriage and breast-feeding.

Concomitant administration of live attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) and measles, mumps, rubella (MMR) vaccine: Randomized study in toddlers in Taiwan

BACKGROUNDnJapanese encephalitis (JE) is the most important cause of viral encephalitis in Asia.nnnMETHODSnIn this randomized, open-label, multicenter trial in 550 children aged 12 to 18 months in Taiwan, children received one dose of JE-CV and one dose of MMR vaccine. Vaccines were either administered separately 6 weeks apart (Groups JE-CV and MMR, named after which vaccine was given first), or concomitantly (Group Co-Ad). JE neutralizing antibody titers were assessed using PRNT50. MMR antibody levels were determined by ELISA.nnnRESULTSnAll groups had low seroprotection/seropositivity rates (<10%) before vaccination for all antigens. Forty two days after vaccination, on either Study Day 42 or 84, seroconversion rates for all antigens were high in all groups, irrespective of the order of vaccinations. Seroconversion for JE ranged from 96.9% in Group Co-Ad on D42 to 100% in Group MMR. Non-inferiority was demonstrated for all analyses as the lower bound of the 95% CI of the difference in seroconversion rates between groups was above the pre-defined limit of -10.0%. The immune responses remained high for all antigens and well above the level of protection 12 months after vaccination in all groups. There were no safety concerns.nnnCONCLUSIONSnJE-CV is safe and induces a strong protective immune response which persists over 1 year when co-administered with MMR vaccine.

Epidemiology of acute otitis media among young children: A multiple database study in Taiwan

BACKGROUND/PURPOSEnAcute otitis media (AOM) is a common complication of upper respiratory tract infection (URTI) among children. The purpose of this study was to evaluate the epidemiology of AOM among young children in Taiwan, including the age incidence and seasonality by combining multiple databases.nnnMETHODSnTwo country-based questionnaire survey studies had been conducted to evaluate the experience of otitis media (OM) among young children: one in 2007 and the other between 2005 and 2010. The number of OM cases (5% of population younger than 7 years) in 2005 and annual visiting rates for URTI from 2005 to 2010 obtained from the National Health Insurance Research Database of Taiwan were collected and comprised the third database. The fourth database comprised ambulatory visits of children with OM to a medical center in central Taiwan between 2005 and 2010.nnnRESULTSnData from a total of 1099 questionnaires were entered into Database I in 2007, and data from 9705 questionnaires between 2005 and 2010 comprised Database II. There were 86,702 children (younger than 7 years, representing 5% of the whole population for this age group) retrieved from Database III in 2007, and 5,904 cases of OM in children between 2005 and 2010 in a hospital. In Database I, 7.46% children experienced at least one episode of AOM compared with 9.21% in Database II for children aged 5 years and younger. In Database III, 13.2% children younger than 7 years had AOM in 2005. The peak season of AOM among children was from March to May (Databases III and IV).nnnCONCLUSIONnAOM was thought to be a very common disease among children; however, this comparative analysis showed that the overall prevalence of AOM among children younger than 5 years was only 20%, much lower than in other countries. AOM was more prevalent during the spring season, and still was similarly common after age 2 years.

Recommendations for Rotavirus Vaccine

Rotavirus infection has been the leading cause of gastroenteritis among children in Taiwan. Studies have shown that 40% of hospitalization for acute gastroenteritis can be prevented through the use of vaccines, including a live, attenuated monovalent rotavirus vaccine and a pentavalent, human-bovine reassortant rotavirus vaccine. In 2009, the World Health Organization suggested that rotavirus vaccine should be included in all national immunization programs. This review summarizes issues and recommendations discussed during an expert meeting in Taiwan. The recommendations included: (1) rotavirus vaccine should be offered to all healthy infants (including those without contraindications, such as immunodeficiency) at an appropriate age; (2) either monovalent or pentavalent vaccine can be administered concurrently with routine injected vaccines; (3) the administration of rotavirus vaccine must be administered at least 2 weeks prior to oral polio vaccination; (4) the first vaccine dose for infants should be administered between age 6 weeks and age 14 weeks 6 days and the course should be completed by age 8 months 0 day; (5) pentavalent vaccines can be administered at 2 months, 4 months, and 6 months while monovalent vaccines can be taken at 2 months and 4 months; (6) a combined use of monovalent and pentavalent vaccine is justified only when the previous dose is unavailable or unknown; and (7) rotavirus vaccines may be given to premature infants, human immunodeficiency virus infected infants and infants who have received or are going to receive blood products.

Recommendations for the management of children with H1N1 novel influenza infection.

As a member of orthomyxoviridae family, influenza viruses are enveloped viruses containing eight RNA segments. The main antigenic determinants of influenza A and B viruses are two surface glycoproteins, the hemagglutinin (H) and the neuraminidase (N). A genetic reassortment between influenza A viruses from different animal hosts may lead to an antigenic shift and thereby increase the risk of a potential pandemic. H1N1 and H3N2 subtypes of influenza A have been circulating all over the world as seasonal influenza since the last H3N2 pandemic in 1968.1 In April 2009, the Centers for Disease Control and Prevention of the United States identified two cases of human infection with the H1N1 novel influenza virus. The greatest initial burden of critical illness and deaths occurred in Mexico between March and June 2009. The virus is a triple-reassortant containing gene segments from swine influenza virus, human influenza virus, and avian influenza virus. Genes for hemagglutinin and neuraminidase come from swine influenza virus.2 On June 11th, 2009, the World Health Organization raised the level of influenza A (H1N1) pandemic alert from phase 5 to 6, as sustained communitylevel transmission of the virus is taking place in more than one region of the world. Recommendations for the Management of Children With H1N1 Novel Influenza Infection