Unraveling the Impact of Pneumococcal Conjugate Vaccines on Ambulatory Antibiotic Drug Consumption in Young Children: An Interrupted Time-Series Analysis

Abstract

Background: Pneumococcal conjugate vaccines (PCVs) reduce respiratory infections in young children, the main antibiotic consumers. Following PCV implementation, dispensed antibiotic prescription (DAP) rates in young children were expected to decline.

Methods: Computerized data on DAP for children <5 years were examined during a 13-year period (including 4 pre-PCV years). All DAPs from clinics with ≥50 insured children, active both pre- and post-PCV implementation were included. Interrupted time-series with segmented regression was applied to analyze monthly DAP rate trends, adjusted for age, ethnicity, and season. Incidence rate ratios (IRRs) of DAPs during the late PCV13 period versus 4 years pre-PCV were calculated both as absolute rate ratios (aIRRs) and relative to expected rates (rIRRs).

Results: Of 1 090 870 DAPs, 57% were in children <2 years. All-DAP rates peaked in the cold season. Post-PCV7/PCV13 implementation, all DAP rates abruptly and significantly declined, reaching a plateau within 5 years. This was largely driven by amoxicillin/amoxicillin-clavulanate (75% of DAPs). Age <2 years and Bedouin ethnicity were significantly associated with higher pre-PCV DAP rates but with faster and greater decline post-PCV, achieving near elimination of gaps between ages and ethnic groups. Overall reduction (95% CIs) in DAP rates per 1000 was estimated between aIRR (344.7 [370.9-358.4]) and rIRR (110.4 [96.9-123.7]) values.

Conclusions: Shortly following PCV implementation, overall DAP rates showed an abrupt, steep decline, stabilizing within 5 years, in parallel to post-PCV respiratory infection trends previously described in this population, suggesting causality. The variable patterns of certain drug categories suggest additional influences beyond PCV.

Keywords: antibiotic consumption; children; community; impact; pneumococcal conjugate vaccines.