Work

Genetic diversity and impact of vaccination on influenza A (H1N1)pdm09 in Mar del Plata, Argentina: a 2015–2020 molecular epidemiological study

Year: 2025

Type: article

Abstract: Background Influenza A viruses are a major cause of viral respiratory infections in humans, leading to a spectrum of diseases ranging from mild to severe, particularly in high-risk groups. Monitoring the frequency and evolution of A (H1N1)pdm09 viruses is essential for guiding vaccine strain selection and maintaining vaccine effectiveness.Objectives To characterize the evolution of circulating influenza A (H1N1)pdm09 strains in Mar del Plata(MDQ), Argentina, and estimate vaccine efficacy from 2015 to 2020, before the SARS-CoV-2 pandemic.Methods We analyzed 46 influenza A (H1N1)pdm09 strains detected by RT-PCR from patients with acute respiratory infections in MDQ between 2015 and 2020. Phylogenetic analysis was performed using maximum likelihood, and vaccine efficacy was estimated with the Pepitope model.Results Seven genetic clades were identified: 6B in 2015, 6B.1 in 2016–2017, 6B.1A, 6B.1A.1, and 6B.1A.3 in 2018, 6B.1A.5A in 2019–2020, and 6B.1A.5a.2 in 2020. Genetic diversity and regional clustering suggested multiple strain introductions from other Argentinian regions or countries. The predicted vaccine efficacy was highest when the frequency of influenza A (H1N1)pmd09 was below 2%, decreasing as viral frequency increased, due to mutations occurring particularly in haemagglutinin epitopes B, C, and E.Conclusion Our findings highlight the dynamic evolution of influenza A (H1N1)pdm09 in MDQ and emphasize the importance of continuous molecular surveillance and regular vaccine updates. Additionally, the Pepitope model proved useful in estimating vaccine efficacy. The impact of vaccination in reducing viral frequency when circulating and vaccine strains are well-matched further supports annual influenza vaccination recommendations to minimize viral burden in the community.

Source: Scandinavian Journal of Infectious Diseases

DOI: 10.1080/23744235.2025.2466118

Authors: Osvaldo Uez, Andrés Culasso, Andrea Lerman, Carlos Cimmino, Rodolfo Campos, Débora Natalia Marcone

Institutions: Administración Nacional de Laboratorios e Institutos de Salud, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Pontificia Universidad Católica Argentina

Language: English

Topic: Influenza Virus Research Studies

Subfield: Epidemiology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green

Funder: Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación