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Invasive Pneumococcal Disease in Latvia in PCV10 Vaccination Era, 2012-2018
Larisa Savrasova1, Angelika Krumina2, Hedija Cupeca3
1Centre for Disease Prevention and Control of Latvia, The European Programme for Intervention Epidemiology Training (EPIET), Riga Stradinš University, Riga, Latvia.
Insights
Invasive pneumococcal disease (IPD) incidence decreased in Latvia following PCV10 vaccine introduction. However, serotype replacement and increased mortality risk from specific serotypes like Streptococcus pneumoniae serotype 3 highlight ongoing challenges.
Area of Science:
- Epidemiology
- Infectious Diseases
- Vaccinology
Background:
- Invasive pneumococcal disease (IPD) poses a significant public health concern.
- Latvia introduced pneumococcal conjugate vaccines (PCV7, then PCV10) for infants, while adult vaccination remains absent from the national program.
- Surveillance data is crucial for monitoring IPD trends and vaccine effectiveness.
Purpose of the Study:
- To describe the incidence and serotype distribution of IPD in Latvia from 2012 to 2018.
- To investigate serotypes associated with fatal outcomes from IPD.
- To assess the impact of infant vaccination programs on IPD epidemiology.
Main Methods:
- Retrospective population-based cross-sectional study utilizing national IPD surveillance data.
- Analysis of laboratory-confirmed IPD cases reported to the Center for Disease Prevention and Control of Latvia.
- Calculation of incidence by age and sex, case fatality rates, and serotype trends, including statistical analysis for trends and associations with mortality.
Main Results:
- A total of 466 IPD cases were reported between 2012 and 2018, with incidence peaking in 2015 and declining by 2018.
- Infants and the elderly exhibited the highest mean annual IPD incidence.
- A decreasing trend in PCV10 vaccine serotypes was observed, alongside increasing trends in PCV23nonPCV13 and non-vaccine serotypes, indicating serotype replacement.
- The overall case fatality rate was 19%, with Streptococcus pneumoniae serotype 3 identified as a significant risk factor for death after adjusting for age.
Conclusions:
- Surveillance data reveal evidence of serotype replacement following infant vaccination, with a rise in non-vaccine and less effectively covered serotypes.
- Streptococcus pneumoniae serotype 3 and advanced age are independently associated with fatal IPD outcomes.
- Further research into Streptococcus pneumoniae carriage is recommended to better understand serotype circulation dynamics and inform future public health strategies.
Abstract:
In 2010 in Latvia, invasive pneumococcal disease (IPD) became a cause for concern and vaccination of infants with four doses of 7-valent pneumococcal conjugate vaccine (PCV7) commenced. In 2012, 10-valent pneumococcal conjugate vaccine (PCV10) (three doses at 2, 4, and 12-15 month of age) vaccination was introduced. We described incidence and serotype distribution of IPD in Latvia and investigated serotypes associated with death from IPD based on surveillance data. Adult vaccination against pneumococcal infection is not included in the national immunization program. Laboratory confirmed IPD cases are passively notified to the Center for Disease Prevention and Control of Latvia (CDPC) by laboratories and clinicians. We calculated incidence by age, sex, case fatality, and trend in serotypes by conducting a retrospective population-based cross-sectional study based on national IPD surveillance data. From 2012 to 2018 466 cases of IPD were reported. The highest notified incidence was in 2015 at 4.4/100,000, which fell to 3.9 in 2018. The highest mean annual IPD incidence was in infants (4.8) and in the elderly (6.0). PCV10 vaccine serotypes were the most prevalent in IPD cases up to 2015 with a decreasing trend from 50% (20/40) in 2012 to 19% (14/74) in 2018 (chi2 test for trend of odds = 0.000). PCV23nonPCV13 vaccine serotypes had an increasing trend and rose from 18% (7/40) to 34% (25/74) (chi2 test for trend of odds = 0.000). Non-Vaccine serotypes had an increasing trend and rose from 13% (5/40) to 27% (20/74) (chi2 test for trend of odds = 0.038). Reported total case fatality was 19% (87/466). The highest, at 36% (20/56), was reported in 2013. After adjusting for age, Streptococcus pneumoniae serotype 3 was associated with death from IPD (adjusted OR 2.3 95%CI 1.25-4.12 p 0.007). Surveillance data indicate evidence of serotype replacement with an increasing trend of serotype 19A and PPV23nonPCV13 and Non-Vaccine serotypes. Serotype 3 and age were associated with fatal IPD outcome. Further studies of S. pneumoniae carriage would be useful in providing more evidence to characterize serotypes' circulation.
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