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. Author manuscript; available in PMC: 2011 Nov 29.
Published in final edited form as: Vaccine. 2010 Oct 23;28(51):8077–8084. doi: 10.1016/j.vaccine.2010.10.023

Figure 1. Serum HI response to influenza vaccination decreases with age.

Figure 1

Figure 1

Figure 1

A. Sera isolated from subjects of different ages, before (t0) or after vaccination (t28), were collected and analyzed in HI assay to evaluate antibody production to vaccine. Results are expressed as fold-increase in titer after vaccination, calculated as follows: titer values after vaccination/titer values before vaccination. Thirty-seven subjects were evaluated, 29 young and 8 elderly. Two young subjects were not included because they were considered outliers (HI values >2 SDs above the mean). The dashed horizontal line indicates the threshold of a positive response in the HI test, which corresponds to 4-fold increase in the serum titer. Spearman’s rho =−0.449, p=0.005 (two-tailed). B. Sera isolated from the blood of 23 subjects of different ages (19 young and 4 elderly) at t0, t7 and t28 were tested in HI assay. Results are expressed as fold-increase in titer after vaccination, calculated as in A. The difference between young and old is significant at both t7 (p=0.040) and t28 (p=0.025), as evaluated by the Wilcoxon test. White columns: young. Black columns: elderly.