Table 3.

Data extraction and conversion of the three outcomes investigated in this review

Influenza antibody response	Turner et al.	Den Elzen et al.	Derhovanessian et al.	Nielsen et al.	Furman et al. study 1	Furman et al. study 2	Furman et al. study 3	Haq et al.	McElhaney et al.	Frasca et al.	Trzonkowski et al.	Strindhall et al.	Reed et al.	Wald et al.	Arias et al.	Moro-Garcia et al.	Guidi et al.
GMR (outcome a)	✔1,2,3	✔8			✔11,12	✔11,12	✔11,12	✔13	✔14	✔15,16		✔		✔21	✔23,24		✔27
Response rate (outcome b)	✔3,4	✔	✔							✔15,16		✔19		✔22			✔
Correlation (outcome c)	✔3,5,6										✔17				✔25	✔22,23,26
Another outcome				✔10							✔18
Model		✔9											✔20

Per study on the effect of CMV-infection on the influenza antibody response to influenza vaccination is indicated what outcome is reported. Numbers refer to footnotes presented in the textbox. ✔Outome is reported. GMR: the geometric mean titer pre-/post-vaccination ratio (GMR) per CMV serostatus group. Response rate: the percentage of subjects with a response per CMV serostatus group. Correlation: the association between influenza and CMV antibody titers. Another outcome: influenza antibody titers were presented in context of CMV in an outcome that was not of interest for this review. Model: the effect of CMV seropositivity on influenza antibody titers was modeled and could not be extracted for this review

¹Data were extracted from a graph reporting the average fold change on a 10log scale (mean and SEM) (outcome a)

²Data were not reported for CMV seropositivity, but for different CMV-seropositive groups based on CMV antibodies. CMV-seropositive high individuals were taken for this review and, therefore, may overestimate the effect of CMV seropositivity in Fig. 4 (outcome a)

³It was unclear in which Brisbane strain (H1N1 or H3N2) an effect was reported and, therefore, we could not categorize the result per influenza strain (Fig. 4) (outcome a)

⁴Data were not reported, but only stated in text that there was no effect for CMV seropositivity on the response rate (outcome b)

⁵Fold increase (of 10 log) of influenza antibodies to vaccination, and not the post-titer, was used in correlation (outcome c)

⁶For the other two influenza strains investigated in  this study, no significant correlation was found but data was not shown so not extracted for this review

⁷Data were modeled for anti-CMV IgG levels and influenza antibody titer (outcome c)

⁸Data were extracted from Table 3 of the article per vaccination strategy and calculated for total group CMV-seropositive and CMV-seronegative individuals

⁹Data were reported as the result of a model for CMV seropositivity corrected for vaccination strategy and others, and were not used for this review

¹⁰Median and range of influenza antibody titers were reported by this study. Of this, no outcomes of interest for this review could be extracted

¹¹Data were presented as a geometric mean titer of three different influenza strains and used in this way in the analysis of this review (Fig. 4)

¹²We could not verify how the geometric mean of three influenza strains per individual was handled in the measurement of spread on group level. Confidence interval of the influenza GMR could not be extracted reliably for this review (outcome A)

¹³Confidence interval of the influenza GMR could not be extracted reliably, since error bars from the graph in the study were too small to measure (outcome A)

¹⁴Data were extracted from a graph reporting the average fold increase and SD (outcome a)

¹⁵Data were extracted from a graph reporting the fold increase per individual for Fig. 5 (outcome A) and post-GMTs as stated in texts were used for Supplementary figure 5

¹⁶Only H1N1 data (negative effect in young and old) were shown, other measured strains were not shown because of ‘low titers’ and, therefore, not included in this review (outcome a and b)

¹⁷Data were analyzed with non-parametric test (Spearman correlation) on non-log-transformed antibody data (for both CMV and influenza antibodies) (outcome c)

¹⁸Mean CMV antibody titers were reported for responders and non-responders to influenza vaccination in this study. Of this, no outcomes of interest for this review could be extracted

¹⁹Data of subject with a pre-titer < 40 or ≥ 40 were pooled for this review

²⁰Data were only reported as the result of a model for CMV seropositivity on combined and normalized influenza antibody titers, so no outcomes could be extracted for this review

²¹Data were extracted from Fig. 2 of the article, by extracting the GMT pre-vaccination and 21-day post-vaccination (outcome A). Although the GMT and 95% CI of day 21 post-vaccination are presented in Fig. 1 according to the article, the 95% CI showed equally distributed error bars on a linear scale, which is questionable and, therefore, no measure of spread was extracted for this review

²²Data were not reported, but only stated in the text that there was no effect of CMV serostatus and only for the young individuals, and could therefore not be extracted for this review

²³Data were reported in arbitrary units (based on an ELISA value divided for time elapsed since immunization) and could not be extracted for any outcome for this review

²⁴Data were not reported for CMV seropositivity, but for different CMV-seropositive groups based on height of anti-CMV IgG level

²⁵Data were reported as a regression model, not as correlation (outcome c)

²⁶Data included the post-titer, and were extracted (outcome c)

²⁷Data only included the post-GMT (Supplementary figure 5), the GMR (outcome a) could thus not be extracted for this review