Advancements in immunization: Acellular pertussis vaccine and the decline of DTP-related adverse events in Chile
Vaccination stands as a highly effective preventive measure against diseases caused by pathogens, yet potential adverse events (AE) may occur, emphasizing the need for robust safety monitoring. Chile employs a passive surveillance system for adverse events following immunization (AEFI), crucial for evaluating vaccine safety. This study aimed to describe the trend in adverse event frequency associated with pertussis vaccines, stratified by whole-cell pertussis vaccine (wP) or acellular pertussis vaccine (aP).
Reporting rates per 100,000 doses administered showed a decline from 40.1 in 2015 to 12.2 in 2020. The most commonly reported AEFI included injection site erythema, pyrexia, and pain at the injection site. Severe adverse events accounted for 5.8% of cases, with 5.9% related to wP vaccines and 5.3% to aP vaccines. Notably, a significant reduction in AEFI reports was observed from 2018 onwards, coinciding with the introduction of the hexavalent DTaP-IPV-HepB-Hib vaccine in the National Immunization Program. This study underscores the importance of continuous monitoring and highlights the potential impact of vaccine-type transitions on adverse event trends.
Abstract
Objectives:
To describe the trend in the frequency of adverse events (AE) records associated with pertussis component vaccines between January 1st, 2015, and June 30th, 2020 in infants younger than 2 years old in Chile, by reviewing the records submitted to the AEFI NIP, stratified by DTP-vaccine type, wP or aP.
Materials and methods:
This was a retrospective observational study including all AEFI records of DTP (either aP or wP)-containing vaccines in the described sample. A descriptive analysis was performed according to vaccine type and AEFI, using MedDRA terminology.
Results:
The total number of AEFI reports was 1,697: 815 corresponding to wP vaccines, 417 to aP vaccines, and 465 with unknown type. The reporting rates for the years 2015 to 2020 were 40.1, 56.2, 37.1, 24.7, 19.1, and 12.2 per 100,000 doses administered, respectively. The most reported AEFI were injection site erythema (42.9%), pyrexia (35.7%), and pain at the injection site (29.2%). Among all cases, 5.8% were SAEs (n = 98), 5.9% were SAEs for wP vaccines (n = 48) and 5.3% were for aP vaccines (n = 22).
Discussion:
A significant decrease in AEFI reports was observed as of 2018, the year that the DTaP-IPV-HepB-Hib was introduced in the NIP.
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