How fast does Covid vaccine protection wear off? New data from the Zoe Covid Study, published today, tries to quantify the extent to which the Pfizer and AstraZeneca vaccines wane over time. It’s a comprehensive study that accounts for PCR test data from over a million double-jabbed people. The results? After roughly six months, Pfizer protection against symptomatic illness fell from 88 per cent to 74 per cent.