Cochrane Style Manual 2.0
And/or

Avoid using ‘and/or’ as it is not explicit. Try rephrasing the sentence; for example, 'fever and/or headache …' to 'fever or headache, or both …'. 'And/or' may be acceptable where rephrasing would make the reading cumbersome; for example, 'fever and/or headache and/or nausea …'.