Abstract
We estimated the direct, indirect and total effects of the 13-valent pneumococcal conjugate vaccine (PCV13) on invasive pneumococcal disease (IPD) in children. A population-based cohort study followed children aged between 2.5 and 59 months between 2001 and 2014 in Navarra, Spain. IPD incidence was compared by PCV status and period. All cases diagnosed from July 2010 to December 2014 and eight matched controls per case were analysed to estimate the adjusted direct effect of PCV13. A total of 120,980 children were followed and 206 IPD cases were detected. Compared with unvaccinated children in the baseline period (2001-2004), overall IPD incidence in 2011-2014 (76% average PCV coverage) declined equally in vaccinated (total effect: 76%; hazard ratio (HR): 0.24; 95% confidence interval (CI): 0.14-0.40) and unvaccinated children (indirect effect: 78%; HR: 0.22; 95% CI: 0.09-0.55). IPD incidence from non-PCV13 serotypes increased among vaccinated children (HR: 2.84; 95% CI: 1.02-7.88). The direct effect of one or more doses of PCV13 against vaccine serotypes was 95% (odds ratio: 0.05; 95% CI: 0.01-0.55). PCV13 was highly effective in preventing vaccine-serotype IPD. The results suggest substantial and similar population-level vaccine benefits in vaccinated and unvaccinated children through strong total and indirect effects.
Highlights
The 7-valent pneumococcal conjugate vaccine (PCV7) has proved highly effective in preventing invasive pneumococcal disease (IPD) caused by the serotypes included in its formulation [1,2]
Higher valency pneumococcal conjugate vaccines (PCVs) containing 10 (PCV10) and 13 (PCV13) serotypes were licensed on the basis of non-inferiority of immunogenicity compared with PCV7 [5]; post-licensure studies are required to assess their effects under real-life conditions
Taking the period of PCV7 use (2005–2009) as the reference, we evaluated the effect of PCV13 in 2011–2014, obtaining an estimate of the indirect protective effect in unvaccinated children of 70% (HR: 0.30; 95% confidence interval (CI): 0.12–0.77) and a total effect in children with PCV13 of 61% (HR: 0.39; 95% CI: 0.22–0.70) against all-serotype IPD
Summary
The 7-valent pneumococcal conjugate vaccine (PCV7) has proved highly effective in preventing invasive pneumococcal disease (IPD) caused by the serotypes included in its formulation [1,2]. To date (June 2015), there are few studies published on the direct effect of PCV13 against IPD, and all except one have used the indirect cohort method and have been limited to evaluating it against vaccine serotypes rather than total IPD [6,7,8]. PCVs can reduce IPD incidence among unvaccinated individuals as a result of reduced transmission This indirect or ‘herd’ effect has been studied in unvaccinated age groups [9,10,11,12], but not in children targeted for vaccination. The total effect accounts for both the direct and indirect effects on vaccinated individuals [13,14]
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