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. 2023 Aug 21;15(8):1780.
doi: 10.3390/v15081780.

Assessing the Intense Influenza A(H1N1)pdm09 Epidemic and Vaccine Effectiveness in the Post-COVID Season in the Russian Federation

Anna Sominina  1 , Daria Danilenko  1 , Andrey B Komissarov  1 , Maria Pisareva  1 , Artem Fadeev  1 , Nadezhda Konovalova  1 , Mikhail Eropkin  1 , Polina Petrova  1 , Alyona Zheltukhina  1 , Tamila Musaeva  1 , Veronika Eder  1 , Anna Ivanova  1 , Kseniya Komissarova  1 , Kirill Stolyarov  1 , Ludmila Karpova  1 , Elizaveta Smorodintseva  1 , Anna Dorosh  1 , Vera Krivitskaya  1 , Elena Kuznetzova  1 , Victoria Majorova  1 , Ekaterina Petrova  1 , Anastassia Boyarintseva  1 , Andrey Ksenafontov  1 , Anna Shtro  1 , Julia Nikolaeva  1 , Mikhail Bakaev  1 , Elena Burtseva  2 , Dmitry Lioznov  1   3
Affiliations

Assessing the Intense Influenza A(H1N1)pdm09 Epidemic and Vaccine Effectiveness in the Post-COVID Season in the Russian Federation

Anna Sominina et al. Viruses. .

Abstract

The COVID-19 pandemic had a profound impact on influenza activity worldwide. However, as the pandemic progressed, influenza activity resumed. Here, we describe the influenza epidemic of high intensity of the 2022-2023 season. The epidemic had an early start and peaked in week 51.2022. The extremely high intensity of the epidemic may have been due to a significant decrease in herd immunity. The results of PCR-testing of 220,067 clinical samples revealed that the influenza A(H1N1)pdm09 virus dominated, causing 56.4% of positive cases, while A(H3N2) influenza subtype accounted for only 0.6%, and influenza B of Victoria lineage-for 34.3%. The influenza vaccine was found to be highly effective, with an estimated effectiveness of 92.7% in preventing admission with laboratory-confirmed influenza severe acute respiratory illness (SARI) cases and 54.7% in preventing influenza-like illness/acute respiratory illness (ILI/ARI) cases due to antigenic matching of circulated viruses with influenza vaccine strains for the season. Full genome next-generation sequencing of 1723 influenza A(H1N1)pdm09 viruses showed that all of them fell within clade 6B.1A.5.a2; nine of them possessed H275Y substitution in the NA gene, a genetic marker of oseltamivir resistance. Influenza A(H3N2) viruses belonged to subclade 3C.2a1b.2a.2 with the genetic group 2b being dominant. All 433 influenza B viruses belonged to subclade V1A.3a.2 encoding HA1 substitutions A127T, P144L, and K203R, which could be further divided into two subgroups. None of the influenza A(H3N2) and B viruses sequenced had markers of resistance to NA inhibitors. Thus, despite the continuing circulation of Omicron descendant lineages, influenza activity has resumed in full force, raising concerns about the intensity of fore coming seasonal epidemics.

Keywords: SARS CoV-2; antigenic properties; genetic analysis; hospitalization; incidence; influenza; molecular detection; monitoring; susceptibility to antivirals.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Weekly PCR detection of influenza viruses in non-sentinel surveillance system in Russia for the period from week 40.2022 to week 20.2023.
Figure 2
Figure 2
Influenza virus detection among SARI patients admitted to hospitals in sentinel surveillance system.
Figure 3
Figure 3
Comparative data of influenza incidence and PCR monitoring in non-sentinel surveillance for seven consecutive seasons.
Figure 4
Figure 4
Three-dimensional antigenic map of influenza A(H1N1)pdm09 viruses isolated in Russia in the epidemic season 2022–2023. Note: Red circles—reference antigens; orange circles—Russian isolates of the current season; green circles—Russian isolates of the previous seasons; grey squares—ferret post-infectious antisera.
Figure 5
Figure 5
Three-dimensional antigenic map of influenza B viruses (Victoria lineage) isolated in Russia in the epidemic season 2022–2023. Note: designations as in Figure 6.
Figure 6
Figure 6
Phylogenetic comparison of HA genes of influenza A(H1N1)pdm09 viruses (ML tree, GTR+GAMMA, constructed with RaxML). Note: Viruses bearing the H275Y mutation in NA (known marker of oseltamivir resistance) are marked with an asterisk (*) at the end of the name. Not all resistant strains are shown in the tree.
Figure 7
Figure 7
Phylogenetic comparison of HA genes of influenza B (Victoria lineage) viruses (ML tree, GTR+GAMMA, constructed with RaxML).
Figure 8
Figure 8
Changes in the level of population humoral immunity to influenza viruses in adults for the period from 2019 to 2022.
See this image and copyright information in PMC

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