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Invasive pneumococcal disease due to 22F and 33F in England: A tail of two serotypes
Zahin Amin-Chowdhury1, Natalie Groves2, Carmen L Sheppard2
1Immunisation and Countermeasures Division, Public Health England, 61 Colindale Avenue, London NW9 5EQ, UK.
Insights
Invasive pneumococcal disease (IPD) caused by serotypes 22F and 33F has a lower mortality risk than IPD caused by PCV13 serotypes. The 15-valent pneumococcal conjugate vaccine (PCV15) could prevent 10% more IPD cases.
Area of Science:
- Infectious Diseases
- Vaccinology
- Epidemiology
Background:
- Invasive pneumococcal disease (IPD) surveillance is crucial for understanding pathogen epidemiology.
- The 13-valent pneumococcal conjugate vaccine (PCV13) is part of the UK childhood immunization program.
- Limited data exists on IPD caused by serotypes 22F and 33F, targeted by the 15-valent pneumococcal conjugate vaccine (PCV15).
Purpose of the Study:
- To investigate the epidemiology, clinical features, and outcomes of IPD caused by pneumococcal serotypes 22F and 33F.
- To compare IPD cases caused by serotypes 22F and 33F with those caused by PCV13 serotypes and other non-PCV13 serotypes.
- To assess the potential impact of PCV15 on reducing IPD burden in England.
Main Methods:
- Enhanced IPD surveillance data from Public Health England (PHE) between 2014/15 and 2018/19.
- Serotyping of invasive pneumococcal isolates and collection of clinical information via general practitioner questionnaires.
- Comparative analysis of IPD incidence, clinical presentation, comorbidities, and mortality rates across different serotype groups.
Main Results:
- Serotype 22F accounted for 7.0% and 33F for 3.5% of IPD cases, with incidence increasing since 2005/06, particularly in older adults.
- Comorbidity prevalence was high for both serotypes (68.7% for 22F, 67.2% for 33F), with invasive pneumonia being the most common presentation.
- IPD caused by serotypes 22F and 33F showed significantly lower odds of death compared to PCV13-type IPD (aOR 0.58 and 0.73, respectively).
Conclusions:
- IPD due to serotypes 22F and 33F is associated with a lower mortality risk compared to PCV13 serotypes.
- Septicemia presentation confers a higher fatality risk than pneumonia in IPD cases.
- PCV15 has the potential to prevent an additional 10% of IPD cases in England, highlighting its public health significance.
Background:
A 15-valent pneumococcal conjugate vaccine (PCV15) aims to protect against serotype 22F and 33F in addition to the serotypes within the 13-valent PCV (PCV13) which was introduced to the UK childhood immunisation programme in April 2010. Little is known about the specific epidemiology, clinical features or outcomes of invasive pneumococcal disease (IPD) due to these two serotypes.
Methods:
Public Health England (PHE) conducts enhanced IPD surveillance in England. Hospital laboratories routinely submit invasive pneumococcal isolates to PHE for serotyping and enhanced clinical information is collected through questionnaires sent to general practitioners. IPD due to serotypes 22F and 33F diagnosed during 2014/15-2018/19 were compared with IPD due to PCV13 serotypes and remaining serotypes.
Results:
In total, 25,415 isolates (93.4%) were serotyped and questionnaires were completed for 22,097 (86.9%) cases. Serotype 22F was responsible for 1,788 (7.0%) and serotype 33F for 893 (3.5%) cases compared to 19.9% (n = 5,047) for PCV13 and 69.6% (n = 17,687) for the remaining serotypes. IPD incidence increased for both serotypes since 2005/06, especially in older adults, but plateaued after PCV13 introduction. Comorbidity prevalence was 68.7% (n = 1,037) for serotype 22F and 67.2% (n = 505) for serotype 33F, with invasive pneumonia being the most common clinical presentation 1,067/1,482; 72.0%, and 514/755; 68.1%, respectively. There were 3,617 deaths within 30 days of disease onset, including 236 (CFR, 15.4%) among 22F, 128 (CFR, 16.5%) among 33F and 21.3% (925/4,350) among PCV13-type IPD cases. When compared with PCV13-type IPD, serotype 22F (aOR 0.58, 95%CI 0.49-0.68, p < 0.001) and 33F (aOR 0.73, 95%CI 0.59-0.91, p = 0.004) were independently associated with lower odds of death. The major circulating sequence types (STs) in 22F (ST 433, ST698) and 33F (ST717, ST100, ST673) were not associated with an increased risk of death compared to the other STs.
Conclusions:
Serotype 22F and 33F-type IPD are associated with a lower risk of death compared to PCV13-type, with those presenting with septicaemia more likely to have a fatal outcome compared to pneumonia. PCV15 has the potential to prevent up to an additional 10% of IPD cases in England.
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