Decreasing case fatality rate following invasive pneumococcal disease, North East England, 2006-2016

Abstract

Declining mortality following invasive pneumococcal disease (IPD) has been observed concurrent with a reduced incidence due to effective pneumococcal conjugate vaccines. However, with IPD now increasing due to serotype replacement, we undertook a statistical analysis to estimate the trend in all-cause 30-day case fatality rate (CFR) in the North East of England (NEE) following IPD. Clinical, microbiological and demographic data were obtained for all laboratory-confirmed IPD cases (April 2006-March 2016) and the adjusted association between CFR and epidemiological year estimated using logistic regression. Of the 2510 episodes of IPD included in the analysis, 486 died within 30 days of IPD (CFR 19%). Increasing age, male sex, a diagnosis of septicaemia, being in ⩾1 clinical risk groups, alcohol abuse and individual serotypes were independently associated with increased CFR. A significant decline in CFR over time was observed following adjustment for these significant predictors (adjusted odds ratio 0.93, 95% confidence interval 0.89-0.98; P = 0.003). A small but significant decline in 30-day all-cause CFR following IPD has been observed in the NEE. Nonetheless, certain population groups remain at increased risk of dying following IPD. Despite the introduction of effective vaccines, further strategies to reduce the ongoing burden of mortality from IPD are needed.

Keywords: Case fatality rate; Streptococcus pneumoniae; invasive pneumococcal disease; mortality; pneumococcal infection; pneumococcal vaccine.

Fig. 1.

Crude 30-day all-cause case fatality rate, adjusted average predicted probabilities and incidence of invasive pneumococcal disease by epidemiological year (April–March) in North East England, April 2006–March 2016. Bars show incidence. Line indicates average predicted probability of 30-day all-cause mortality for cases presented as case fatality rate (CFR), adjusted for age, sex, clinical presentation, risk factors and pneumococcal serotype. Epidemiological year is April–March. Open squares indicate crude CFR. Error bars indicate 95% confidence intervals.

Fig. 2.

Adjusted predicted probabilities of 30-day all-cause case fatality rate by epidemiological year (April–March) in North East England by age, April 2006–March 2016. Lines indicate predicted probability of 30-day all-cause mortality presented as case fatality rate (CFR) for individuals of specific ages (years) adjusted for sex, clinical presentation, risk factors and pneumococcal serotype using mean values for covariates. Epidemiological year is April–March.