I am a scientist, not a biological scientist but I do have a good understanding of risk as a scientific concept. I haven’t worked on vaccines, unlike WWM’s daughter.
So this is my view. Sorry its an essay.
The mixing of vaccines is not something I am worrying about. The BMJ have asked the NYT to withdraw or clarify the article the published suggesting that vaccines could be mixed, saying that this is not the recommendation at all. So we can discount that for now.
Oxford have trailed their vaccine with different dosing intervals and are not concerned about the dosing recommendation – please correct me if I’m wrong.
So we’re left with Pfizer. None of us were at the MHRA meeting so we can’t know what was said. But what do we know? We know that after 21 days the effectiveness of the Pfizer one is 89%. Not 52% as is often bandied about, because 52% is the average over the first 21 days, because immune response takes some time to happen. Although 52% would still be very good. After 21 days, immune response does not fall off a cliff, at least it doesn’t with immunity in any other situation, so its reasonable to assume the same is true here. Its reasonable to assume that the immunity given by the Pfizer vaccines works the same as immunity from any other source.
On balance of risks, with hundreds of people dying every day and tens of thousands contracting COVID, the MHRA have decided that the risk of a small reduction in immunity, and the risk of vaccine resistant mutations, are outweighed by the risk that thousands of people will die and our NHS will collapse. Its worth noting that is always the MHRA who decide on how a drug will be used, not the manufacturer. (Based on the manufacturer's trials, of course)
We don’t have the luxury of waiting until months of research are in to show us about the interval, and we don’t have the luxury of rolling out the vaccine slower that we could. I hope everyone watches the clip with Whitty because he talks very clearly about the balance of risk, and I agree with him.