I think there are two schools of thought, with little evidence so far to make one dominant. What the press seems to be assuming is that it's as simple as the i

I think there are two schools of thought, with little evidence so far to make one dominant. What the press seems to be assuming is that it's as simple as the immunity from vaccination simply wearing out over time. But there's at least one alternative explanation. The alternative is that the timing of the second dose was less than optimal. With little experimentation to guide the authorities, the 4-week delay was chosen in part to give a quicker timeline for vaccination. If they'd said, say, 2 months or 6 months, then we would have been that much slower getting to even that level of immunity, so it was a conscious compromise. But what if the optimal gap between shots really is 6 months, and because the booster achieves that, the effect will be more permanent? Like I said, not enough is known for sure, but there is some reason to believe that the latter explanation may be true.