Photo Credit: Muhammad Shoaib
The following is a summary of “Genetic diversity and impact of vaccination on influenza A (H1N1)pdm09 in Mar del Plata, Argentina: a 2015–2020 molecular epidemiological study,” published in the February 2025 issue of Infectious Diseases by Uez et al.
Influenza A viruses, notably A(H1N1)pdm09, caused human respiratory infections, necessitating continuous monitoring of the frequency and evolution to ensure effective vaccine strategies.
Researchers conducted a retrospective study to analyze the development of circulating H1N1 pdm09 strains in Mar del Plata (MDQ), Argentina, and assess vaccine efficacy from 2015 to 2020 before the SARS-CoV-2 pandemic.
They examined 46 H1N1 pdm09 strains determined by RT-PCR from individuals with acute respiratory infections in MDQ between 2015 and 2020. Phylogenetic analysis was executed employing the maximum likelihood method, and vaccine efficacy was estimated with the P epitope model.
The results showed that 7 genetic clades were recognized: 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 indicated multiple strain introductions from other Argentinian regions or countries. Predicted vaccine efficacy was highest when H1N1 pdm09 frequency remained below 2%, declining as viral frequency increased due to mutations in haemagglutinin epitopes B, C, and E.
Investigators concluded that continuous surveillance and vaccine updates were essential due to the dynamic evolution of H1N1 pdm09 and that the Pepitope model effectively assessed vaccine efficacy.
Source: tandfonline.com/doi/full/10.1080/23744235.2025.2466118
