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Changes in the Pneumococcal Vaccine Serotypes in Adult Noninvasive Pneumonia after the Introduction of Pneumococcal

Hiroaki Takeda¹, Chisa Sato¹, Chang Bin²

¹Department of Respiratory Medicine, Yamagata Saisei Hospital, Yamagata, Japan.

Journal of Global Infectious Diseases

|March 1, 2019

Insights

Non-vaccine serotypes (NVTs) increasingly cause adult pneumococcal pneumonia, surpassing vaccine types by 2015. This shift may be linked to childhood pneumococcal conjugate vaccine (PCV) use and multigenerational housing.

Area of Science:

Infectious Diseases
Vaccinology
Epidemiology

Background:

Pneumococcal conjugate vaccines (PCVs) have reduced invasive pneumococcal infections in children.
However, serotype replacement, where non-vaccine serotypes (NVTs) increase, remains a concern.

Purpose of the Study:

To investigate the frequency of serotype replacements in adult pneumococcal pneumonia cases.
To analyze the transition from vaccine serotypes (VTs) to NVTs over time.

Main Methods:

A retrospective study of 303 adult patients with pneumococcal pneumonia admitted between 2006 and 2015.
Serotyping using the capsular swelling method and statistical analysis (chi-square tests).

Main Results:

Adult pneumococcal pneumonia cases were predominantly male with underlying conditions and low vaccination rates.
Vaccine coverage declined, and by 2015, NVTs (51.2%) replaced VTs (48.8%) as the predominant cause.
High rates of multigeneration housing were observed.

Conclusions:

NVTs became more frequent in adult pneumococcal pneumonia starting in 2013, exceeding VTs by 2015.
Childhood PCV vaccination and multigenerational housing appear associated with this trend reversal.

Read full analysis

Abstract

Context:

Although the incidence of invasive pneumococcal infections in children has decreased since the introduction of pneumococcal conjugate vaccines (PCVs), the appearance of serotype replacements has continued to increase.

Aims:

We examined the frequency of serotype replacements in adult cases of pneumococcal pneumonia. Furthermore, the transition in the coverage of vaccine serotypes (VTs) to non-VTs (NVTs) was also examined.

Settings And Design:

We investigated all confirmed cases of pneumococcal pneumonia in 303 adult patients admitted to Yamagata Saisei Hospital between April 2006 and March 2015.

Materials And Methods:

Pneumococcal serotypes were determined by testing for a specific type of antiserum using the capsular swelling method.

Statistical Analysis Used:

Chi-square tests were used to compare patient characteristics.

Results:

Annually, the number of admitted patients ranged from 24 to 43, with most of them being men (64.7% of the total patient cohort). Although many cases involved some underlying conditions, the rate of pneumococcal vaccination remained low. The average rate of multigeneration housing was high (37.6%). The rates of pneumococcal vaccine coverage declined since 2013 (7-valent PCV (PCV7), 18.5%; PCV13, 59.3%; and 23-pneumococcal polysaccharide vaccine (PPSV23), 66.7%) and were <50% for each vaccine (PCV7, 4.7%; PCV13, 32.6%; and PPSV23, 48.8%) in 2015. In addition, the VTs were replaced with NVTs in 2015 (48.8% vs. 51.2%).

Conclusions:

The frequency of NVTs in adult pneumococcal pneumonia increased in 2013, with the frequency exceeding that of the vaccine forms in 2015. Regular PCV vaccination of children and multigeneration housing seem to be associated with this reversed trend.

Keywords:

Adult generation housing pneumococcal pneumonia replacement serotype vaccines

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