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Peter English #FBPE Profile picture
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5 Jan, 6 tweets, 2 min read
How big a hurdle is it to get a license for a slightly modified version of a licensed vaccine?
1/6
One of the advantages of the genomic-driven development of mRNA and vector vaccines is that it is relatively straightforward to modify the base sequences to keep up with pathogen mutations.
2/6
In this 10 tweet thread, @DrEricDing discusses concerns that evolution of SARS-CoV-2 might lead to variants which are not recognised (as effectively) by the immune system following previous infection or vaccination. threadreaderapp.com/thread/1346241…
3/6
In the final tweet (10) he writes “Scientists… have said they are testing the vaccines against the new variants and say they could make any required tweaks in around six weeks.”
4/6
This fits with my understanding of the science and technology.

But, once the vaccine has been "tweaked", what are the implications for licensing the modified vaccine?

Presumably it doesn't have to be treated as a completely new product.
5/6
But how great a hurdle is it to get a "tweaked" vaccine licensed?
6/6
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More from @petermbenglish

Peter English #FBPE Profile picture
4 Dec 20
@sweetanimo @patricia_stoop @abcdiagnosis I have seen some of your conversation on Twitter about the use of Covid-19 vaccines in people who are immune-suppressed, and thought I might be able to help.
1/11
First, the UK guidance, including on contraindications etc., is conveniently all in one place - in the public domain - in the "Green Book", via gov.uk/government/pub…
2/11
But first, let's consider how and why immunosuppression might be an issues with a vaccine.
3/11
Read 13 tweets
Peter English #FBPE Profile picture
3 Dec 20
Thisk, on lateral flow testing "false positives" is from DH guidance, and strikes me as extremely stupid. assets.publishing.service.gov.uk/government/upl…
@deeksj @jackiecassell

1/4
It says the test is "99.6% specificity (meaning four false positives per thousand tests)". (It doesn't mean that actually: it's four false positives per thousand tests that should have been positive - not the same thing at all. Confusing sensitivity and predictive values.)
2/4
But that isn't the stupidest thing.

It then says you can use a test with sensitivity of <70% (in the real world >30% of true positive cases give a false negative result) as a confirmatory test, and cease isolation if the second test is negative.
3/4
Read 4 tweets
Peter English #FBPE Profile picture
1 Dec 20
Hi @ScienceShared and @mugevic!

Let's say the reproduction interval is about 4 days. That's the interval between the onset of symptoms in case 1 and the onset in case 2 (on average).
1/10
Patients are most infectious before the onset of symptoms. So, if case 1 develops symptoms, they will probably already have infected at least half of the secondary cases.

And some of them will already be infectious and have infected tertiary cases.
2/10
Few people will get tested on the day of onset of symptoms. Most of the time the onset of symptoms is identified retrospectively. After all, symptoms are mostly common to many other minor viral infections.
3/10
Read 10 tweets
Peter English #FBPE Profile picture
30 Nov 20
We keep banging on about "test and trace" for #Covid-19.

But it's pointless.

With a reproduction interval of only 4-6 days, if you wait for a test result before isolating contacts, you will do it too late. They will already have spread the infection.
1/2
And many cases are asymptomatic, so you'll miss them, anyway.

Testing is too unreliable. Too many false negatives, and too short a time from infection to infectiousness.

The only thing which works is keeping people apart so they can't transmit it.
2/2
"given the
potential delays in isolation of patients, even the early
detection and isolation strategy might not be fully effective
in containing SARS-CoV-2."

thelancet.com/journals/lanmi…

@mugecevik et al
Read 4 tweets
Peter English #FBPE Profile picture
30 Nov 20
I seem to have been saying this internally within @PHE_uk and predecessor organisations forever.

Every time there's a major event and they ask for feedback, we tell them "Email does not work. It gets /we get overwhelmed. We can't keep up and feel guilty. It's stressful."
1/6
We frequently get the same message once from the original sender, and then four more times from people concerned we might have missed it; and then we have to try to work out if we're looking at an updated version...
2/6
And sometimes the delays mean that we receive older versions after newer ones... It is a disaster!
3/6
Read 6 tweets
Peter English #FBPE Profile picture
30 Nov 20
Hi @ajpollard1 @OxfordVacGroup !

What does "ChAdOx1 vector is modified to be replication deficient" mean?

Can it induce production of antigen proteins if it doesn't replicate at all?

Does the lack of replication reduce the immune response to the vector?
1/3
Are ChAdOx1 vector vaccines contraindicated where live virus vaccines are contraindicated (and why [not]?)

Where can we find a New Scientist level explanation of these things?
2/3
If it is "replication deficient", how do you produce it? Can you culture it?

Parenthetic thought:
Are viruses ever "live", and where does this vector vaccine fit? Is it a Schrödinger's virus, alive or dead, depending on your reason for asking?
3/3
Read 4 tweets

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