Where we currently stand on vaccines vs. variants

If you were wondering where we are currently on vaccine efficacy and virus variant spread, in amongst all the other data hitting our newsfeeds, a recent British report stands out.

The University of Oxford and the Office for National Statistics has produced a study into the effectiveness of the Pfizer/BioNTech and AstraZeneca vaccines (the two most widely-used vaccines in the UK) against the Delta variant (now by far the most common virus variant worldwide).

We already knew that the Pfizer vaccine is 92% effective against the Delta variant, which is, of course, excellent. What this new updated study tells us, though, is that this efficacy drops to 78% just three months later. AstraZeneca, on the other hand, only showed an efficacy of 69% at first, but after three months this had only fallen to 61%. The researchers estimated that after 5 months the two vaccines may be about equally efficacious against the variant. 

The study did not look at the Moderna or Johnson & Johnson vaccines, but it seems likely that Moderna will behave similar to Pfizer, and J&J will behave similar to AstraZeneca. The reasons behind the differences are not entirely clear, but likely stem from the very different ways in which mRNA and viral vector vaccines work.

This sharp drop-off in efficacy for Pfizer may be part of the reason why Israel, which largely relied on Pfizer vaccinations, has seen a large increase in cases recently, despite one of the fastest and most comprehensive vaccination drives in the world. Either way, it has muddied the picture still further. Like we really need that right now. It may also add ammunition to the calls for contentious third booster doses, like US President Joe Biden recently called for, despite most of the world not having even had one.