Or is that a silly question? My teen (one vaccine so far, booster soon) today has a temperature and saying they ache all over. Paracetamol not doing much, only alternating with nurofen is helping. Last temp was 38.9. LFT this evening is negative. Can I presume it won’t ‘become’ covid or could it be possible to test negative and say tomorrow test positive or is he likely safe from covid does anyone know? He is obviously at home and not school.