Will vaccine efficacy decline over time?

Data emerging from Israel suggests that booster vaccines may be more urgent than first thought. Immunity might be waning for those who got their jab in the winter months, according to figures from the Israeli Ministry of Health. The analysis shows that someone over 60 who received their second dose in January is three times more likely to be reinfected than an over-60 jabbed in May. On the surface, it sounds like bad news. Yet in reality, it is nothing that we wouldn’t expect.

While we collectively gawped at the speed and efficiency of their rollout, the Israelis are the first global example of long-term Covid vaccine effect. We have to be careful when jumping to conclusions. Nevertheless, there are several questions we should ask. Waning immunity is certainly one explanation for their observations. But surely it was the vulnerable who were vaccinated earliest? What is the age of those infected and subsequently hospitalised? Does combining all over-60s into one group account for the different health profiles among them? How does the Delta (Indian) variant influence this pattern? More analysis will inevitably follow to flesh this out.