Impact of Seven Valent Pneumococcal Conjugate Vaccine on Nasopharyngeal Carriage in Young Children in Okinawa, Japan

Hideki Akeda¹, Bin Chang², Yoshihisa Nakamura³, Hirotsune Hamabata⁴, Kenji Ameku⁵, Takaya Toma⁶, Eiichi Tamanaha⁷, Makoto Ohnishi²

¹Okinawa Prefectural Nanbu Medical Center & Children’s Medical Center, Okinawa, Japan.
²Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan.
³Nakamura Clinic Pediatric, Dermatology and Internal Medicine, Okinawa, Japan.
⁴Awase Daiichi Clinic, Okinawa, Japan.
⁵Syuri Child Clinic, Okinawa, Japan.
⁶Wanpaku Clinic, Okinawa, Japan.
⁷The Okinawa Society of Child Health, Okinawa, Japan.

DOI: 10.4236/wjv.2015.52011                

Abstract

In Japan, the heptavalent pneumococcal conjugate vaccine (PCV7) became available in February 2010 and was subsidized by the national funding system from May 2011 in Okinawa, after which it was incorporated into the national immunization practice (NIP) in April 2013 using a 3 + 1 schedule for all infants. We conducted an annual survey in 2012 to determine the effect of PCV7 on nasopharyngeal colonization by pneumococcal serotypes and to analyze the risk factors for colonization in infants. Nasopharyngeal swabs for pneumococcal isolation and serotyping were obtained from infant 2 to 22 months of age before and after PCV7 immunization among 4 clinics in Okinawa, Japan. Between January 2012 and December 2012, nasopharyngeal swabs for bacterial cultures were obtained among 782 infants aged 2 to 22 months old and demographic data was obtained among 725 participant infants. Among the 725 evaluable infants, 193 pneumococcal strains were detected in 180 infants for an overall nasopharyngeal carriage of 24.8%. The main capsular serotypes isolated were 6C (16.1%), 19A (12.4%) and 15B (9.8%). Carriage of PCV7 serotypes accounted for 21.8% (42/193). The result of multivariate data analysis showed the pneumococcal carriage rate of non-PCV7 serotypes was significantly (P < 0.001) high in infant with siblings and daycare attendance. On the other hand, the result of multivariate data analysis showed that carriage rate of PCV7 serotype had only significantly high risk in infant with siblings and did not have a significant risk dependent on age and daycare attendance. Carriage PCV7 serotypes increased in the presence of other siblings, while PCV7 vaccination was shown to eliminate daycare attendance as a risk. The results of this study demonstrates that PCV7 vaccination decrease the overall nasopharyngeal carriage of PCV7 serotypes in vaccinated children including children at risk such as children attending day-care centers.

Keywords

Nasopharynx, Carriage, Pneumococcal Conjugate Vaccine, Japan, Young Children

Conflicts of Interest

The authors declare no conflicts of interest.

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