THREAD on vaccine effectiveness:

Public Health England released its updated report on real world effectiveness of Pfizer & AZ in England this week.
assets.publishing.service.gov.uk/government/upl…

I thought would be helpful to explain what they found...

TLDR: pretty good! 1/9
Firstly, both vaccines work almost equally well, so going to treat them as one in below.

Secondly, will focus on effect of ONE dose in OVER 80 year olds (most data!).

Effectiveness is higher in younger people and after second dose. 2/9
Right, so let's consider two lots of over 80s - 100,000 people in each group.

One group is unvaccinated and the other is more than two weeks out from their first dose.

(There seems very little real world protection for first two weeks after vaccination!!) 3/9
In the unvaccinated group, about 300 people might get symptomatic Covid. Exactly how many depends on how much Covid there is around, but let's go with 300 for now (0.3%).

Of those 300, 45 might need to go to hospital with Covid and 40 might die from Covid. 4/9
So what about the over 80s who've had one dose of vaccine?

Well, it offers about 60% protection from getting symptomatic Covid (ie feeling sick from Covid).

So, instead of 300, only about 120 out of the 100K might get sick with Covid. 5/9
For those 120 vaccinated people with Covid, they get *further* protection from needing hospital (35%-45%) or dying (55%).

So, only 10 out of the 120 might need hospital, and only 7 out of the 120 might die. 6/9
So *overall*, after one dose, an 80+ yr old person is 75%-80% less likely to need hospital from Covid and 80%-85% less likely to die from Covid compared to someone who has not been vaccinated.

This is GOOD! 7/9
As a comparison, seat belts + air bags are ~70% effective at preventing death from car accidents.

pubmed.ncbi.nlm.nih.gov/21720604/

You definitely want to wear a seat belt & have an air bag, but you still want to drive safely!

After 1 dose of vaccine you still want to be sensible. 8/9
Plus, just as you drive safely to protect others on the road as well as yourself, being sensible with Covid precautions protects those who haven't been vaxxed or for whom it doesn't work well (e.g. some cancer patients), because the vaccines do reduce transmission too. 9/9
PS H/T to @adsquires for the seat belt analogy :-)

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More from @chrischirp

20 Mar
THREAD on EUROPE:
Many headlines today about Europe's third wave, what it means for us and, in particular, international travel.

thetimes.co.uk/article/surge-…

Some thoughts about what it means... 1/11
Firstly, the current increases in Europe are because B117 (the Kent strain) has become dominant there - move than 70% in Denmark, NL, 50-70% in France, Belgium, Itlay, Germany & Austria. 2/11
As with us in Dec, they didn't act decisively to stop its spread - instead they've been in semi-restrictions (similar to our tier 3) - enough to bring *down* cases of old variant but not enough to stop B117.

B117 was only 5-10% in EU early Feb 3/11
Read 12 tweets
20 Mar
THREAD on SCHOOLS:

It's now 4 weeks since Scotland & Wales started a phased return to primary schools (secondary schools went back last week) & 2 weeks since all schools in England went back.

What is happening? 1/15
First let's look at Wales. They started sending young kids back to nursery and primary schools 22nd Feb. Older primary school kids & secondary school went back last week.

Wales publish new Covid incidents in schools - and (unsurprisingly) incidents are increasing. 2/15
Secondly, Scotland. There we have case data by age.

Primary school kids only get a test if they get symptoms. School staff can get tested without symptoms if they want. All positive cases from lateral flow device tests (LFDs) are PCR confirmed.

Testing has stayed flat. 3/15
Read 18 tweets
17 Mar
THREAD on vaccination slowdown story:

TLDR: Don't panic!

Tonight a reduction is vaccine supply is being widely reported leading to a pause in rolling out vaccination to the under 50's... bbc.co.uk/news/uk-politi… 1/5
Basically, we gave about 11 million people their first dose mid Jan - mid Feb. They need their 2nd dose by end April.

We've been vaxxing about 2.5m/wk last few weeks, but let's say vax supply drops to about 2m/wk for April. Then we need ALL those doses to honour 2nd doses. 2/5
Once most of those are done, we can start rolling out vaccination to new people again (adults under 50) in May.

Assuming we can ramp up to 3.5m/wk from May, we can still offer everyone a 1st dose by mid July. 3/5
Read 6 tweets
17 Mar
THREAD on schools in England so far & what next:

Context:
A few million people already do Lateral Flow Device tests (LFDs) for work each week.

On 8th March schools reopened and secondary school students were asked to 3 LFDs at school - 2 last week and 1 early this week.
People with symptoms of Covid continue to get a single PCR tests.

People who test positive after taking LFDs at *home* or for health & care work can also get a PCR test to confirm the result.

People taking LFDs at work, at school or in a test centre do NOT get confirmatory PCR
IMPORTANT: PCR test results take a while to come through, so we can only ever use positive results from 4 or more days ago.

LFD test results report immediately, and so, where there is no confirmatory PCR, we can use test results up to yesterday.
Read 12 tweets
13 Mar
THREAD on Lateral Flow Device tests (LFDs):

They are being used more and more in England.

Thread about how they're used, why you NEED confirmatory PCR testing, how it will make interpretating case figures difficult as we open up.

#NerdyThread 1/19
LFDs are used to test people who don't have Covid symptoms - they give results in about 30 minutes.

The govt reckons about 30% of people with Covid don't have symptoms & this article suggested that asymptomic spread might account for 50% of cases.
jamanetwork.com/journals/jaman… 2/19
So the point is to find people who have Covid but don't know they have Covid & stop them mixing with, and potentially infecting, other people. 3/19
Read 23 tweets
12 Mar
THREAD on VACCINATIONS: how are we doing in England?

Although this week has seen fewer jabs, we've still given a dose to 2.5 million people over last 7 days.

It's also good to see 2nd doses starting to take off & 42% of people over 16 have had a dose.🍾

BUT some concerns 1/6
There are differences in coverage by deprivation. For over 70s, the differences are definitely there but high coverage in all groups.

The differences are starker by ethnicity, with black populations having the lowest coverage. 2/6
As ages get younger, the disparities by deprivation & ethnicity get more pronounced. Although coverage is still increasing for 65-69 year olds, it seems likely that coverage in most deprived populations will stay much below that of the least deprived & lower than 70+s. 3/6
Read 6 tweets

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