The latest Public Health England (PHE) weekly vaccine surveillance report appeared on Thursday (another one is due tomorrow).
I wasn’t holding out high hopes for this instalment, after digging down into the method used the previous week and finding it didn’t control adequately for background incidence (so confounded vaccine effectiveness with natural decline) and applied such brutal adjustments it could turn a 4% effectiveness into a 73% one. It lived down to expectations.
The authors appear still to be working out what exactly their reports are for as each of the three to date presents different information in a slightly different way. While the first was largely a summary of evidence published elsewhere, the second served more as a showcase for PHE’s latest study and focused on effectiveness against symptomatic disease in the over-65s (90%, supposedly). This week, the over-65s are gone and the focus is on effectiveness against the Indian variant. This makes reading the reports quite confusing, as each doesn’t feel so much like an update to the previous one as a stand-alone report on a separate topic.
In between Report 2 (for week 20) and Report 3, a separate PHE study was published on the
Indian Delta variant which found the effectiveness of full vaccination against symptomatic Covid reduced from 93% to 88% with Pfizer and 66% to 60% with AstraZeneca when the Indian Delta variant was involved versus the British Alpha variant.
As I noted last week, this 66% effectiveness of AstraZeneca (against the
British Alpha variant) was a long way below the 90% in the over-65s claimed in Report 2. It’s probably a sign of how low my opinion is of PHE vaccine studies that I was pleasantly surprised to see this discrepancy actually make an impact on the data presented in Report 3, and you can see below in the AstraZeneca two-doses box (top right) week 20’s “85-90%” has become “65% to 90%” in week 21. There is still no explanation from PHE, however, as to why one of their studies finds AstraZeneca 90% effective against symptomatic infection in the over-65s while another finds it is just 66% effective in all ages. Is this not the kind of discrepancy that should occasion comment from the authors?