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Table 1 Vaccination history and completeness of data in cases, controls and controls with severe medical conditions.

From: Effectiveness of a MF-59™-adjuvanted pandemic influenza vaccine to prevent 2009 A/H1N1 influenza-related hospitalisation; a matched case-control study

 

Used cut off for exposure

Cases

Controls

Controls with severe medical conditions

Crude vaccination coverage

 

46% (68/149)

46% (13012/28238)

53% (5752/10830)

Known vaccination date in vaccinees

 

49% (33/68)

100% (13012/13012)

100% (5752/5752)

Exposed cases (known vaccination date)

> 7 days

> 14 days

48% (16/33)

33% (11/33)

60% (7798/13012)

29% (3715/13012)

58% (3320/5752)

27% (1551/5752)

Assumed exposed cases (unknown vaccination date)

> 7 days

> 14 days

49% (17/35)

31% (11/35)

NA

NA

NA

NA

(Assumed) vaccination coverage

> 7 days

> 14 days

22% (16+17/149)

15% (11+11/149)

28% (7798/28238)

13% (3715/28238)

31% (3320/10830)

14% (1551/10830)

  1. Data using different cut offs for the validity of vaccination are presented. Note that no direct comparison of vaccination coverage between cases and controls should be made because of the matching in which each stratum contains a single case.
  2. * NA = not applicable as for all controls, date of vaccination was available.