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. 2021 Oct 14;12:748264. doi: 10.3389/fimmu.2021.748264

Figure 5.

Figure 5

Relationship between pre-existing titers and fold-increase 21 days post-vaccination. Correlation between baseline titers and fold-increase (FI) of titers on day 21 post-vaccination (day 21/day 0) for endpoint (A–D), NAI (E–H) and PRNT50 titers (I–L) in the repeated group. Health care workers (HCWs) were vaccinated with H1N1pdm09 and two or three trivalent influenza vaccines (TIVs) during influenza seasons 2009/2010 – 2013/2014. The antibody responses have been grouped by the vaccine number that were administered. All vaccinated HCWs in the repeated group is included in this figure regardless of their vaccination intervals. Open circles represent HCWs that were vaccinated the previous season and crossed circles represent HCWs that had chosen to not be vaccinated the previous season. The correlation coefficient (rs) was calculated by non-parametric Spearman correlation.