Elsevier

Vaccine

Volume 36, Issue 50, 29 November 2018, Pages 7744-7752
Vaccine

The changing epidemiology of invasive pneumococcal disease after PCV13 vaccination in a country with intermediate vaccination coverage

https://doi.org/10.1016/j.vaccine.2018.05.026Get rights and content

Abstract

Background

We studied the impact of 13-valent pneumococcal conjugate vaccine (PCV13) on the incidence of invasive pneumococcal disease (IPD) and serotype distribution in a region with intermediate levels of vaccination (around 64% in children aged <2 years).

Methods

Surveillance data on IPD cases reported by microbiologists participating in the Microbiological Reporting System of Catalonia during 2006–2014 were analysed. We compared estimated incidence rate (IR) ratios for serotypes included in PCV7, PCV10non7, PCV13non10 and non-PCV13 between the PCV7 (2006–2009) and PCV13 periods (2010–2014). IR were corrected for missing serotypes according to year and age groups: <2 years, 2–4 years, 5–64 years and ≥65 years.

Results

A total of 9338 IPD cases were reported. Overall IPD incidence declined by 26.2% (from 16.4 to 12.1) in the PCV13 period. The largest decrease was observed in children aged 2–4 years (44.5%, from 37.4 to 20.8). Pneumonia fell in all age groups with the largest reduction in children aged 2–4 years (49.3%) and <2 years (42%). PCV13 serotypes decreased significantly in all age groups, from 52% (31.6 to 15.1) in children aged 2–4 years to 35% (22.8 to 14.8) in adults aged ≥65 years. Non-PCV13 serotypes rose by 13% (14.8 to 16.8) in people aged ≥65 years.

Conclusions

In a region with intermediate vaccination coverage, the introduction of PCV13 has reduced the overall incidence of IPD, mainly due to the decrease in PCV13 serotypes in all age groups, suggesting herd immunity. Non-PCV13 serotypes have increased in adults aged ≥65 years, suggesting serotype replacement. Higher PCV13 vaccination coverage in children will further reduce IPD incidence in all age groups.

Introduction

Invasive pneumococcal disease (IPD) is a major cause of morbidity and mortality in children and the elderly [1]. Vaccination with the 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in Europe in 2001. In countries including PCV7 in the vaccination schedule there was a significant decrease in IPD incidence, mainly due to reductions in PCV7 serotypes in children aged <5 years, and in other age groups in which indirect effects were observed [2], [3]. However, replacement by non-PCV7 serotypes was observed in vaccinated children, mainly caused by serotypes 19A and 7F [4], [5]. PCV7 was replaced by the 10-valent pneumococcal conjugate vaccine (PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13) to provide protection against additional serotypes.

Before July 2016, neither PCV7 nor PCV13 was included into routine vaccination schedule in Catalonia. Both vaccines were recommended by the Vaccination Advisory Committee of the Spanish Association of Pediatrics when they were licensed [6]. However, prior to July 2016, the governmental health plan paid for pneumococcal vaccination only for children younger than 5 years old with selected risk factors.

As vaccination of infants with pneumococcal conjugate vaccines may influence the distribution of serotypes in adults, changes in serotype distribution in this age group should be monitored. Until the PCV13 became available for adults, the 23-valent pneumococcal polysaccharide vaccine (PPV23) was recommended for people aged ≥65 years and <65 years at increased risk of IPD in the United States [7] and several European countries [8].

The objective of this study was to assess the impact of PCV13 on the incidence of IPD and serotype distribution in all age groups in a region with intermediate levels of pneumococcal conjugate vaccination.

Section snippets

IPD surveillance system

Catalonia is a region in the northeast of Spain with a registered population of 7,518,903 in 2014, distributed as follows: 147,572 children aged <2 years, 248,228 children aged 2–4 years, 5,785,820 people aged 5–64 years and 1,337,283 aged ≥65 years [9].

In July 2016, PCV13 was included in the Catalan vaccination schedule. The estimated PCV7 coverage in children aged <5 years with one or more doses in 2007–2009 was 58.7% (80.2% of them fully vaccinated) [10]. In 2013 the estimated coverage of

Baseline characteristics

Overall, 9338 IPD cases were reported between 2006 and 2014, of which 5461 (58.5%) were male. The age distribution was: 706 (7.6%) in the <2 years, 614 (6.6%) in the 2–4 years, 4137 (44.3%) in the 5–64 years and 3840 (41.1%) in the ≥65 years age groups. The age was unknown in 41 cases (0.4%). The mean age increased from 49.07 years (SD: 29) to 54.78 years (SD: 27.96) in 2006–2009 and 2010–2014, respectively (p < 0.001).

Pneumonia was the most common clinical presentation (73.9%, of which

Discussion

The overall incidence of IPD decreased by 26% in 2010–2014, mainly in children aged <5 years but also in non-vaccinated age groups. The overall reduction in IPD incidence was due to a reduction in specific PCV13 serotypes (44%) in both, the vaccinated and non-vaccinated age groups, which suggests that vaccinating children indirectly protected adults via herd immunity. In contrast, there was an increase in some non-PCV13 serotypes, suggesting serotype replacement, especially in adults aged

Conclusions

After the introduction of PCV13 vaccination, a decrease of 26% in the overall incidence of IPD was observed due to the reduction in PCV13 serotypes, suggesting herd immunity. Non-PCV13 serotypes increased in adults aged ≥65 years, suggesting serotype replacement.

Intermediate vaccination coverage provides fewer direct and indirect benefits than those observed in countries with greater coverage rates. Higher PCV13 vaccination coverage in children will further reduce IPD incidence in all age

Conflicts of interest

The authors have no conflicts of interest to declare.

Acknowledgements

This study was partially funded by SpIDnet (Assessing the impact of vaccination with the conjugate vaccines on the epidemiology of invasive pneumococcal disease in Europe), a network funded by the European Centre for Disease Prevention and Control; the Catalan Agency for the Management of Grants for University Research (AGAUR Grant number 2017/SGR 1342); the Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP CB06/02/0076); and the Centro de Investigación

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