Published online Aug 8, 2016. doi: 10.5409/wjcp.v5.i3.311
Peer-review started: May 20, 2016
First decision: June 6, 2016
Revised: July 12, 2016
Accepted: July 20, 2016
Article in press: July 22, 2016
Published online: August 8, 2016
AIM: To investigate evidence of clinical protection in infants after one dose of 7-valent pneumococcal conjugate vaccine (7vPCV) owing to carrier priming.
METHODS: Using Australian National Notifiable Diseases Surveillance System data, we conducted a descriptive analysis of cases of vaccine type invasive pneumococcal disease (VT-IPD) during “catch-up” years, when 7vPCV was carrier primed by prior administration of DTPa vaccine. We compared the number of VT-IPD cases occurring 2-9 wk after a single dose of 7vPCV (carrier primed), with those < 2 wk post vaccination, when no protection from 7vPCV was expected yet. Further comparison was conducted to compare the occurrence of VT-IPD cases vs non-VT-IPD cases after a single carrier-primed dose of 7vPCV.
RESULTS: We found four VT-IPD cases occurring < 2 wk after one carrier primed dose of 7vPCV while only one case occurred 2-9 wk later. Upon further comparison with the non-VT-IPD cases that occurred after one carrier primed dose of 7vPCV, two cases were detected within 2 wk, whereas seven occurred within 2-9 wk later; suggesting a substantial level of protection from VT-IPD occurring from 2 wk after carrier-primed dose of 7vPCV.
CONCLUSION: This data suggest that infants may benefit from just one dose of 7vPCV, likely through enhanced immunity from carrier priming effect. If this is proven, an adjusted 2-dose schedule (where the first dose of PCV is not given until after DTPa) may be sufficient and more cost-effective.
Core tip: With the inclusion of newer conjugate vaccines with higher number of serotypes in the immunisation schedule, literature suggests that prior immunisation with tetanus/diphtheria-containing vaccines could enhance the immunogenicity of subsequently administered glycoconjugate vaccine, a phenomenon known as “carrier priming”. This analysis provides evidence of substantial clinical protection ensued after one dose of 7-valent pneumococcal conjugate vaccine as result of carrier priming. This phenomenon could be implemented to enhance the immunogenicity of conjugate vaccines among vulnerable populations such as infants in resource-poor settings, travellers, immigrants and refugees.