Effectiveness of 7- and 13-Valent Pneumococcal Conjugate Vaccines in a Schedule Without a Booster Dose: A 10-Year...

Area of Science:

• Public Health
• Vaccinology
• Epidemiology

Background:

• Australia's unique infant pneumococcal conjugate vaccine (PCV) schedule uses 3 primary doses without a booster (3+0).
• This schedule initially utilized 7-valent PCV (PCV7) from 2005, transitioning to 13-valent PCV (PCV13) in 2011.
• Vaccine effectiveness (VE) and waning were assessed for both PCV7 and PCV13 under this schedule.

Purpose of the Study:

• To measure the vaccine effectiveness (VE) of PCV7 and PCV13 in Australia using a 3+0 infant schedule.
• To evaluate the waning of protection offered by these vaccines over time.
• To determine if a booster dose is necessary to maintain protection against invasive pneumococcal disease (IPD).

Main Methods:

• Utilized a case-control study design with IPD notifications and age-matched controls from the Australian Childhood Immunisation Register.
• Employed an indirect cohort method using IPD cases from non-vaccine serotypes as controls.
• Calculated VE using logistic regression and assessed waning by examining the odds of vaccine-type IPD in the 12-36 months post-primary vaccination period.

Main Results:

• Both PCV7 and PCV13 demonstrated high initial VE in infants: 92.9% for PCV7 and 86.5% for PCV13.
• A significant increase in the odds of vaccine-type IPD was observed from 12 months post-dose 3, indicating waning protection.
• Waning occurred for both PCV7 and PCV13, with odds of IPD increasing significantly by 24-36 months post-vaccination.

Conclusions:

• The 3+0 infant PCV schedule, while initially effective, shows progressive increases in breakthrough invasive pneumococcal disease (IPD) cases post-PCV13.
• Waning immunity suggests that the current 3+0 schedule may not provide sustained protection.
• A booster dose of PCV13 in the second year of life is recommended to maintain protection against IPD.