I've been talking to the government's scientific advisers about the outlook for Covid-19 and I've emerged feeling pretty gloomy - and concerned that we face a gruelling and nerve-wracking six months.
It's about the risks associated with mutations of the virus. Rather than gloss or interpret what they say, I might as well quote directly.
I started by asking what kind of danger the kind of mutations we've seen in South Africa and in Manaus, Brazil pose here.
One influential scientist said: "Manaus and South Africa had both reached herd immunity, as far as we can tell. Both had very high levels of serological evidence of infection. Then the new strains emerged.
"I would say that it is a very strong possibility that natural infection with the old strains does not give much protection against either of these strains (which have many similarities)".
So what does this mean for the effectiveness of the Pfizer and AstraZeneca vaccines?
"By deduction we might expect the vaccines to be much less effective against these strains too, but we don't know that for certain", the scientist said, which is troubling.
This of course explains why the government is desperate to keep the new strains off these shores - why it has insisted no one can come to the UK without first taking a Covid-19 test, and why it has been considering closing the borders altogether to travellers from abroad.
But all this may be too late, or just not sufficient to protect us.
Here again is a member of the government's Scientific Advisory Group on Emergencies (SAGE): "The SA strain is very similar [to the Manaus one] and is already here, and probably spreading.
"And 'our' [Kent] mutation is basically half-way to the SA/Manaus one. Given we have so many cases at the moment, it does seem likely that our strain will mutate to something quite a lot like the SA/Manaus one".
So what's to be done?
Here is what one of his distinguished colleagues told me: "I'm hoping we vaccinate everyone over 50 before it's an issue here.
"Not that vaccine will be a panacea (esp with the Manaus strain or similar), but it will help.
"Overall I am quite a lot gloomier than 6 weeks ago! But trying to find a silver lining". None of this is to say that all the news is bad - although the news I disclosed earlier on Friday that the government's NERVTAG committee's believes the Kent strain is 1.3 times more lethal than the old strain is also very worrying.
It is reassuring that in the UK as a whole, the virus appears to be shrinking (though not yet conspicuously so in the Midlands and the North).
But with far too much coronavirus still knocking around and the diminution not occurring at any great speed, it matters that a vaccine-resistant mutation is kept at bay.
For what it is worth, immunologists tell me they think the existing vaccines will probably reduce the risk of acute illness in many people even if they are infected with the mutations we know about.
But they acknowledge there is just too much uncertainty for comfort around all this.
Which is why the PM has lately been warning that we can't be certain our lives will feel anything like normal for many months yet.
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