Reviewed by Hannah Imlay, MD MS; University of Utah
The pneumococcal conjugate vaccines (PCV7 and PCV13) have led to lower cases of invasive pneumococcal disease in France, but ongoing updates to the vaccine will likely be needed to continue to prevent cases of invasive disease.
A recent study published in Lancet Infectious Diseases examined 76,000 cases of invasive Pneumococcal diseases (IPD) (meningitis and bacteremia) across 17 years of surveillance in France. The authors performed a quasi-experimental interrupted time series using prospective surveillance data collected over 17 years (Jan 2001-Dec 2017) encompassing the time periods of the rollout of PCV7 and PCV13. The authors split this time frame into 5 time periods according to PCV implementation and measured the incidence rate of IPD diagnoses over each of these periods. Serotype was determined for all meningitis isolates, non-meningitis isolates in children, and 25% of non-meningitis isolates in adults (overall, 31% of cases were serotyped).
Adults ≥65 years old accounted for around 50% of cases, and children <15 years old accounted for around 10% of cases in all time periods. Non-meningitis cases made up 90% of IPD cases in all time periods. PCV7 introduction only resulted in small changes in overall incidence; however, the early post-PCV13 period was characterized by a significant decrease in cases (-1.5% monthly change, [95% CI -2.2, -0.8] p<0.0001) and the late post-PCV13 period was characterized by a significant increase in cases (+1.8% monthly change [1.0, 2.6], p<0·0001). This trend was present across both meningitis and non-meningitis cases, and across multiple age groups.
Serotype replacement was evident in this cohort. PCV7 serotypes accounted for 6.7% of all IPD cases in late PCV13 period vs 49.1% of cases in the period before widespread implementation of PCV7. PCV13 serotypes significantly decreased after PCV13 introduction, but disease due to these serotypes still accounted for 23% of cases in the late PCV13 period (from 47% in the pre-PCV13 period). During the late post-PCV13 period, only 30% of cases were caused by PCV7 or PCV13 serotypes, while 42% of cases were caused by the eight most common non-PCV13 serotypes (8, 22F, 12F, 9N, 24F, 15A, 10A, 15B/C).
Overall, authors estimate that 45,000 cases of IPD were prevented by PCV vaccination; however, the rise of new serotypes suggests that further pneumococcal conjugate vaccines covering more serotypes are required.
Reference:
Ouldali N, Varon E, Levy C, Angoulvant F, Georges S, Ploy MC, Kempf M, Cremniter J, Cohen R, Bruhl DL, Danis K. “Invasive pneumococcal disease incidence in children and adults in France during the pneumococcal conjugate vaccine era: an interrupted time-series analysis of data from a 17-year national prospective surveillance study.” Lancet Infect Dis 2020; 21: 137-47.