Changing Trends of Invasive Pneumococcal Disease in the Era of Conjugate Pneumococcal Vaccination in Olmsted County: A Population-Based Study.

ABSTRACT

OBJECTIVE: To estimate the incidence of invasive pneumococcal disease (IPD) in the pre-13-valent pneumococcal conjugate vaccine (pre-PCV13; 7-valent pneumococcal conjugate vaccine era, 2002-2010) and post-PCV13 (2011-2018) time periods. PATIENTS AND METHODS: Using the Rochester Epidemiology Project, we conducted a population-based cohort study of all IPD cases in Olmsted County, Minnesota, from January 1, 2002, to December 31, 2018. RESULTS: Overall, 187 cases of IPD were identified. The incidence of IPD decreased significantly from 11.1 (95% CI, 9.1 to 13.2) to 5.6 (95% CI, 4.3 to 6.9) per 100,000 person-years when the pre- and post-PCV13 periods (2002-2010 vs 2011-2018) were compared (P<.001). Of the 187 patients with IPD, 112 (59.9%) had previously received at least 1 dose of pneumococcal vaccine. Among the IPD cases in the post-PCV13 period, there was an increase in non-PCV13 serotypes, mainly 11A (from 1.0% [1 of 105] to 6.2% [4 of 64]) and 33F (from 2.9% [3 of 105] to 15.6% [10 of 64]), while PCV13/non-7-valent pneumococcal conjugate vaccine serotypes declined from 38.1% (40 of 105) to 15.6% (10 of 64). At 30 days after an IPD diagnosis, the survival rate was 88.8% (95% CI, 84.4% to 93.4%). CONCLUSION: A marked decline in IPD incidence occurred during the post-PCV13 era. Because of the observed increase in non-PCV13 serotypes, coupled with multiple factors that impact the epidemiology of IPD, ongoing surveillance of patients with IPD, particularly due to non-PCV13 serotypes, is warranted.