That's what they are saying but a number of doctors have come out saying we shouldn't be waiting 12 weeks, WHO are saying the same and the companies making them say they were tested at 3 weeks apart. So we don't even know if this is effective practice and could be costly in the long run.
Actually WHO are not saying that. If you read
what they actually say it's to play by the book unless there are “exceptional circumstances of vaccine supply constraints and epidemiologic settings to delay the administration of the second approach for a few weeks in order to maximise the number of individuals benefiting from a first dose". When you're at war you sometimes have to not do things by the book, but the people who like to do things by the book will always complain. In this case it's more than just people wanting to do things by the book, it's clearly a gamble, but I think it's a gamble that worth taking.
This
BMJ article (or
the BBC here) gives a good overview of the arguments, and
the BMJ have published the view of a group of sceptics led by a surgeon. Broadly the immunologists seem pretty happy that it shouldn't affect the working of the vaccine, if anything the limited data we have suggests that the Oxford-Zeneca vaccine works better with a longer gap. On the flip side, the BioNTech-Pfizer vaccine may not persist so long in the bloodstream which would give less time ("only" 4 weeks or so) for an immune reaction, but it seems to work so well that it's probably OK.
The sceptics include :
Some virologists who are worried about the 12-week regime giving more scope for new mutants to arise. Always a worry - but the possibility of new mutants has to be traded against the certainty of more deaths from a 3-week gap and the fact that new mutants seem to be arising anyway.
GMC and GPs worrying about the short notice of the switch, and the ability of the admin system to cope with rearranging lots of appointments (and the effect on those who get messed around). Obviously it would help if we had a government who didn't treat everything like a last-minute essay crisis.
The pharma company lawyers will always worry about multi-£££bn lawsuits unless the book is followed to the letter, so don't expect the companies to say anything other than "do it by the book".
They're not negligible concerns, but I'd still say it's worth the gamble given that eg the BioNTech-Pfizer vaccine gives
89% protection from one jab if you give it 2 weeks for immunity to develop, and the second jab only takes you from 89% protection to 95%.
The COVID actuaries group has published
a basic analysis of the different priority groups, summarised in the table below. For the sake of argument say we can jab a constant 2m people per week. So in 6 weeks, you can either vaccinate 6 million people twice, so giving 95% protection to the over 80s and most healthcare workers, or you can vaccinate 12 million people once and give 89% protection to almost all shielders and over 70s.
The first group account for 68% of deaths, the second group account for 88% of deaths, so as a very crude calculation using the BioNTech-Pfizer vaccine at 6 weeks rather than 3 weeks would reduce deaths by nearly 14%. Since we're running at over 8000 deaths per week at the moment that means moving from 3 weeks to 6 weeks will save over 1000 deaths per week, moving to 12 weeks saves 100-200 more.
The significance of the 12 week gap is that there are 20.5 million people in the groups that account for 97% of deaths - over 60, healthcare etc workers or high-risk under 60's - and we jabbed 2.5 million in the last week, so potentially in 12 weeks we could jab everyone in the groups that have 97% of the deaths, plus key groups like the million who work in schools. That prize is worth the gamble in my view - it's a combination of the vaccines giving good protection after 1 jab, the ability to jab all the high-risk groups within 12 weeks and the current huge death toll - 14% of the death toll in August would be a dozen a week, which would reduce the pressure to take this gamble.