!Pre-exposure PRN ≥1052
|-
!Non-cases with <br>≥1 symptom‡
|26 non-cases<br>(720%)
|11 non-case
|-
!Non-cases with <br>no symptom
|11 non-case<br>(31%)
|24 non-cases
|}
::&daggerDagger;suggestive of subclinical infection::Fisher's exact χ<sup>2</sup> test ''p''<0.001002