Covid Delta variant

  • #1
Evo
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Summary:
The Delta variant is serious. Here’s why it's on the rise.
The virus variant that caused infections to spike in the U.K. is now spreading in the U.S., and experts are very worried
Get vaccinated!

This week, the Centers for Disease Control and Prevention officially declared the Delta variant, a coronavirus strain first detected in India, “a variant of concern.” This designation is given to variants shown to be more transmissible than the original strain, that can cause more severe disease and potentially reduce the effectiveness of treatments or vaccines.

Why was the Delta variant classified as a variant of concern?

The Delta variant, also referred to as B.1.6.1.7.2 [and] believed to have originated from India, is one of the most concerning variants … It is more likely to lead to disease, hospitalizations and possibly death.

The Delta variant looks like it might be up to 60 percent more infectious, which is why the CDC really put a bold label forward in calling it a variant of concern. They only do that when they think a variant is concerning enough that it could change the course of a disease or potentially pose a threat to someone who gets it.

https://www.yahoo.com/news/the-covid-19-delta-variant-what-you-need-to-know-151035628.html

The Delta variant already accounts for 18 percent of cases in Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming, and about six percent of cases nationwide. It has already spread to more than 70 countries and is now the most dominant variant in India, the United Kingdom, and Singapore. Last week, Delta caused more than 90 percent of the new COVID-19 cases in the U.K., leading to a 65 percent bump in new infections since May 1. On Monday, to curb Delta’s spread, the U.K. government decided to postpone “freedom day,” which would mark the end of public health restrictions.

The Delta variant is 60 percent more transmissible than the Alpha variant—first identified in the U.K.—which in turn was about 50 percent more transmissible than the ancestral Wuhan strain. “It’s a super spreader variant, that is worrisome,” says Eric Topol, founder and director of the Scripps Research Translational Institute. It has features that enable escape from the immune system and is perhaps more evasive than the Beta variant (B.1.351) first identified in South Africa, which was the worst until now, says Topol. “Plus, it has the highest transmissibility of anything we've seen so far. It's a very bad combination.”

Dismayed by the trajectory of Delta in the U.K., Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, warned President Joe Biden last week, “we cannot let that happen in the United States.”

The President echoed those sentiments, tweeting “Folks, the Delta variant—a highly infectious COVID-19 strain—is spreading rapidly among young people between 12 and 20 years old in the U.K. If you’re young and haven’t gotten your shot yet, it really is time.” A complete dose of a COVID-19 vaccine is still effective at preventing serious COVID-19 stemming from Delta infection.

https://www.nationalgeographic.com/...20210618&rid=6BB08808740E9FEDD2938054BB46CA41
 
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  • #2
Ygggdrasil
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Preliminary data from Public Health England suggests 88% effeciveness of the Pfizer vaccine against the delta variant (B.1.617.2) vs 93% effectiveness against the alpha variant (B.1.1.7), so despite initial worries, the vaccines do still work well against this variant -- more reason to get vaccinated if you have not already.

Effectiveness of COVID-19 vaccines against the B.1.617.2 variant
https://khub.net/documents/13593956...iant.pdf/204c11a4-e02e-11f2-db19-b3664107ac42

Abstract
Background The B.1.617.2 COVID-19 variant has contributed to the surge in cases in India and has now been detected across the globe, including a notable increase in cases in the UK. We estimate the effectiveness of the BNT162b2 and ChAdOx1 COVID-19 vaccines against this variant.

Methods A test negative case control design was used to estimate the effectiveness of vaccination against symptomatic disease with both variants over the period that B.1.617.2 began circulating with cases identified based on sequencing and S-gene target status. Data on all symptomatic sequenced cases of COVID-19 in England was used to estimate the proportion of cases with B.1.617.2 compared to the predominant strain (B.1.1.7) by vaccination status.

Results Effectiveness was notably lower after 1 dose of vaccine with B.1.617.2 cases 33.5% (95%CI: 20.6 to 44.3) compared to B.1.1.7 cases 51.1% (95%CI: 47.3 to 54.7) with similar results for both vaccines. With BNT162b2 2 dose effectiveness reduced from 93.4% (95%CI: 90.4 to 95.5) with B.1.1.7 to 87.9% (95%CI: 78.2 to 93.2) with B.1.617.2. With ChAdOx1 2 dose effectiveness reduced from 66.1% (95% CI: 54.0 to 75.0) with B.1.1.7 to 59.8% (95%CI: 28.9 to 77.3) with B.1.617.2. Sequenced cases detected after 1 or 2 doses of vaccination had higher odds of infection with B.1.617.2 compared to unvaccinated cases (OR 1.40; 95%CI: 1.13-1.75).

Conclusions After 2 doses of either vaccine there were only modest differences in vaccine effectiveness with the B.1.617.2 variant. Absolute differences in vaccine effectiveness were more marked with dose 1. This would support maximising vaccine uptake with 2 doses among vulnerable groups.

Popular press summary: https://www.bmj.com/content/373/bmj.n1346
 
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  • #4
atyy
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The increased fraction of new infections due to delta is probably not entirely due to it being more transmissible than alpha if there were no vaccinations. Some of it may be because alpha is less transmissible in a vaccinated population.

There's been much more data since May 25, but Jeffery Barrett outlined some of the issues in this tweet.
"Key question for policy, not yet fully answered, is how much due to:
1. vaccine efficacy
2. intrinsic transmissibility
3. human epidemiological factors"

As @Ygggdrasil posted above, the vaccine is still effective against delta, but the second dose is important. So the UK has been trying to bring second doses forward, eg. here is a tweet from Mark Ford on how to check availability, cancel the first appointment, then book an earlier second dose.
 
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  • #5
PeroK
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Scotland and England played out a goalless draw in a soccer match in London, but the real winner is the Delta variant:

1624087127952.png
 
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  • #6
pinball1970
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Scotland and England played out a goalless draw in a soccer match in London, but the real winner is the Delta variant:

View attachment 284685
A super spreader.
Ok, it's outside but that many people for 2 hours, no masks?
They will younger less likely to be vaccinated too.
Awful game too, I stayed in.
 
  • #7
atyy
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A super spreader.
Ok, it's outside but that many people for 2 hours, no masks?
They will younger less likely to be vaccinated too.
Awful game too, I stayed in.
Maybe https://www.bbc.com/sport/football/57404223 ?
Euro 2020: Fans at Wembley games required to show proof of vaccination or negative test before entry

"Uefa says UK-based ticket holders aged 11 or over can show proof of full vaccination, with both doses received at least 14 days before the match.

Those not fully vaccinated must show proof of a negative lateral flow test taken within the previous 48 hours."
 
  • #8
PeroK
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Maybe https://www.bbc.com/sport/football/57404223 ?
Euro 2020: Fans at Wembley games required to show proof of vaccination or negative test before entry

"Uefa says UK-based ticket holders aged 11 or over can show proof of full vaccination, with both doses received at least 14 days before the match.

Those not fully vaccinated must show proof of a negative lateral flow test taken within the previous 48 hours."
The sports venues themselves are taking precautions, but that photograph was taken in Leicester Square - where, if we are being cynical, fans who failed their COVID test and cannot go the stadium will gather, after having crammed maskless onto the national rail and London underground network!

Altogether now: "Bring it on, bring it on, bring it on ..."
 
  • #9
atyy
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The sports venues themselves are taking precautions, but that photograph was taken in Leicester Square - where, if we are being cynical, fans who failed their COVID test and cannot go the stadium will gather, after having crammed maskless onto the national rail and London underground network!

Altogether now: "Bring it on, bring it on, bring it on ..."
Any chance, you think, that it's just English fans, since presumably the Scottish ones would have had to pass or fail their test before travelling?

Hmmm, looking at the photo, looks like Scotland fans? I guess they might have been vaccinated or tested negative before making the trip?

https://www.skysports.com/football/...ans-not-to-travel-to-london-for-wembley-clash

https://www.scotsman.com/sport/foot...e-scotland-vs-england-game-at-wembley-3279081
"Despite police asking fans not to travel unless they have secured a booking in a venue to watch the game, up to 20,000 Scotland fans have travelled to watch Steve Clarke’s team at Wembley."

Huh, maybe you are right!
 
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  • #10
PeroK
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Any chance, you think, that it's just English fans, since presumably the Scottish ones would have had to pass or fail their test before travelling?
There is no government or police action to prevent anyone who has failed a COVID test from doing anything. It's all effectively voluntary cooperation. Excepting the quaratine system for those entering the country in the first place.

In particular, there are no checks on anyone using public transport. Nor is mask-wearing enforced on public transport. Someone could fail a COVID test in Scotland, jump on a train to London, get on the underground and join the crowd in Leicester Square. No one is going to stop them or even ask them to wear a mask.
 
  • #11
atyy
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The vaccine effectiveness estimates for the delta variant cited by @Ygggdrasil were for symptomatic infections (ie. mild cases as well as those requiring hospitalization). There are updates by the UK PHS. For reducing hospitalizations, one dose is about 71% (AstraZeneca) or 94% (Pfizer) effective, and 2 doses are 90+% effective for both vaccines.

https://www.theguardian.com/world/2021/jun/15/the-covid-delta-variant-how-effective-are-the-vaccines
https://www.gov.uk/government/news/...ve-against-hospitalisation-from-delta-variant
 
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  • #12
PeroK
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The vaccine effectiveness estimates for the delta variant cited by @Ygggdrasil were for symptomatic infections (ie. mild cases as well as those requiring hospitalization). There are updates by the UK PHS. For reducing hospitalizations, one dose is about 71% (AstraZeneca) or 94% (Pfizer) effective, and 2 doses are 90+% effective for both vaccines.

https://www.theguardian.com/world/2021/jun/15/the-covid-delta-variant-how-effective-are-the-vaccines
https://www.gov.uk/government/news/...ve-against-hospitalisation-from-delta-variant
And, in the past two weeks we have gone up from about 2,000 positive tests per day to over 10,000 per day. As you can see from the football scenes, the will to battle COVID has drained away and we'll just have to take the Delta variant on the chin.

The Prime Minister has promised full opening up on the 19th of July. It will be interesting to see what happens if the Delta variant is raging at that time.
 
  • #13
atyy
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One thing I don't understand about the UK - it started off with a terrible COVID-19 policy "herd immunity", but now it seems to be doing quite well overall - vaccination rates among the elderly are more than 90%, approaching 98% in some areas - and unlike the US which opened up only because it gave up persuading some a large fraction of its population to vaccinate - the UK, even with the delta variant, has a date for opening up (19 July) that even if delayed another month (till August) would still be based on having a large fraction of its population vaccinated, with extremely high vaccination rates among the vulnerable. So I think it's still looking good, relative to other rich countries. Normally, I would think the better policy would be due to a change in the government's science advisors, but that doesn't seem to have been the case? It's the same advisors, but they "repented" of their sins?
 
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PeroK
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One thing I don't understand about the UK - it started off with a terrible COVID-19 policy "herd immunity", but now it seems to be doing quite well overall - vaccination rates among the elderly are more than 90%, approaching 98% in some areas - and unlike the US which opened up only because it gave up persuading some a large fraction of its population to vaccinate - the UK, even with the delta variant, has a date for opening up (19 July) that even if delayed another month (till August) would still be based on having a large fraction of its population vaccinated, with extremely high vaccination rates among the vulnerable. So I think it's still looking good, relative to other rich countries. Normally, I would think the better policy would be due to a change in the government's science advisors, but that doesn't seem to have been the case? It's the same advisors, but they "repented" of their sins?
I can give you a personal view.

We did well getting in and ordering the vaccines early. The way the vaccination programme started really quickly was a huge success.

We were lucky that the start of mass vaccinations coincided with a trough in the case numbers. In any case, we had about the lowest rate (cases and deaths) among comparible countries for a couple of months.

There was always the chance of something like the Delta variant. You could argue that because we were doing so well, we relaxed on the Indian front. It was only about 40,000 people who flew in from India, I believe. In any case, instead of a minor inconvenience for 40,000 people, we have a resurgent pandemic affecting 68 million.

We seem to have the lowest vaccine hesitancy rate - by some margin over countries like the US and France. That said, without vaccinating children, I don't see that the Delta variant can be stopped. Currently the policy is not to vaccinate children. It's not clear when we will reach the point at which there is no one left who accepts the vaccine (we are currently at nearly 80% of the adult population (18+) have had at least one jab and nearly 60% have had two jabs.)

The UK situation has always been a balance between scientific advice and government policy. That said, we have no extreme mainstream politicians when it comes to COVID. But, generally, the government has always acted too late - it's almost a law of modern democratic politics that you can only act once that action is inevitable and never pro-actively. That's the way I see it. For example, we will only vaccinate children once it's completely clear that we must do it.

Overall, if the Delta variant spreads worldwide, then it could be very grim.
 
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  • #15
atyy
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We seem to have the lowest vaccine hesitancy rate - by some margin over countries like the US and France. That said, without vaccinating children, I don't see that the Delta variant can be stopped.
But do we need it stopped? If vaccination rates among in adults are high enough, and gets to nearly 1`00% in the vulnerable groups, then given that 2 doses of the vaccine are still effective at reducing hospitalizations, even if the variant infects them, the death rate could still be markedly reduced, maybe enough not to stress the healthcare system. I think a similar view is expressed here by Christian Drosten, where the point of vaccination is not so much to prevent transmission, but to prevent severe disease, since we expect more variants to come along with immune escape such that vaccinated people will still become infected, but with much lower rates of severe disease, and higher rates of asymptomatic or mildly symptomatic cases. These asymptomatic or mildly symptomatic people will in turn infect others.
 
  • #16
PeroK
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But do we need it stopped? If vaccination rates among in adults are high enough, and gets to nearly 1`00% in the vulnerable groups, then given that 2 doses of the vaccine are still effective at reducing hospitalizations, even if the variant infects them, the death rate could still be markedly reduced, maybe enough not to stress the healthcare system. I think a similar view is expressed here by Christian Drosten, where the point of vaccination is not so much to prevent transmission, but to prevent severe disease, since we expect more variants to come along with immune escape such that vaccinated people will still become infected, but with much lower rates of severe disease, and higher rates of asymptomatic or mildly symptomatic cases. These asymptomatic or mildly symptomatic people will in turn infect others.
There is another factor: the more people who naturally get the virus, the more chance of further mutations. If we end up with, say, 10 million more people getting COVID in the UK, then we will probably have the Epsilon variant, and whatever that brings. It's much better to limit further cases to as few as possible. If it eventually circulates in low numbers, then that's not the same as an epidemic.

Moreover, no country wants to end up effectively isolated because it has some terrible variant that the rest of the world doesn't want.

Third, it's not clear yet what long term problems there may be with contracting the virus.

Finally, if it takes another 2 months for the UK to fully vaccinate everyone who wants it (and 3 months if we include children), then we ought to try to limit COVID until then. I don't like the idea of COVID raging among those who have not yet had the opportunity to get both jabs. And that's still a lot of people: there are 11 million people in the UK who have had one jab and waiting for the second.
 
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  • #17
pinball1970
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There is another factor: the more people who naturally get the virus, the more chance of further mutations. If we end up with, say, 10 million more people getting COVID in the UK, then we will probably have the Epsilon variant, and whatever that brings. It's much better to limit further cases to as few as possible. If it eventually circulates in low numbers, then that's not the same as an epidemic.

Moreover, no country wants to end up effectively isolated because it has some terrible variant that the rest of the world doesn't want.

Third, it's not clear yet what long term problems there may be with contracting the virus.

Finally, if it takes another 2 months for the UK to fully vaccinate everyone who wants it (and 3 months if we include children), then we ought to try to limit COVID until then. I don't like the idea of COVID raging among those who have not yet had the opportunity to get both jabs. And that's still a lot of people: there are 11 million people in the UK who have had one jab and waiting for the second.
Yes and about 25 million with no jabs. That's a lot of bodies. Edit: I gave the wrong impression I think as I was in a rush. 'bodies' in this context was a reference to a population where the virus could infect unchecked, mutate and lead to something potentially worse than Delta.
That population would be a lot younger than Feb 2020 so less in hospital we would expect (ignoring long COVID) for @Evo
 
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  • #18
atyy
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Finally, if it takes another 2 months for the UK to fully vaccinate everyone who wants it (and 3 months if we include children), then we ought to try to limit COVID until then. I don't like the idea of COVID raging among those who have not yet had the opportunity to get both jabs. And that's still a lot of people: there are 11 million people in the UK who have had one jab and waiting for the second.
I wasn't suggesting not to wait for 2 months. Certainly it's good to make sure everyone above 30 and maybe 20 who wants to be vaccinated has had 2 doses before opening up. My point was that if you could (hypothetically) get 100% coverage for those 30 and above, then there may not be any advantage in recommend vaccination to those below 17.

The reason for vaccinating those 17 and below would be if there's enough vaccine hesitancy in the older age groups. In that case allowing the virus to transmit to them would stress the healthcare system, so it's an advantage to vaccinate youths and children, so that infection doesn't spread so quickly.
 
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  • #19
atyy
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https://www.bbc.com/news/live/uk-57543588
Nick Robinson interviewing Public Health England's Susan Hopkins.

"He asks first what is happening with the spread of the Delta variant in England. ...

Pushed on how many adults needed to be vaccinated by 19 July, to allow restrictions to be lifted, she suggests a figure of 70% could realistically be reached - adding that she is particularly keen to see all adults over 30 in England double-vaccinated by so-called "Terminus Day".

"We know two doses really protects against hospital admissions," she tells Nick Robinson.

She says that if admissions and discharges continue as they are currently, the NHS will be able to cope."
 
  • #20
atyy
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The delta (B.1.617.2) variant has an advantage over the alpha (B.1.1.7) variant in the UK. Secondary attack rates for delta are approximately 1.5 times those for alpha. Part of it is likely due to vaccine being less effective against delta than against alpha. First dose effectiveness for symptomatic disease is approximately 33% against delta, and 51% against alpha. Second dose effectiveness for delta and alpha are 88% and 93% respectively with the Pfizer vaccine; 60% and 66% respectively with AstraZeneca. (See @Ygggdrasil's post #2)

This interesting article by points out that because the UK used such a long interval between first and second doses, the difference in first dose effectiveness might have made a significant contribution to delta's advantage over alpha:
https://theconversation.com/covid-d...a-variant-an-evolutionary-helping-hand-162359
COVID: did a delayed second dose give the delta variant an evolutionary helping hand?
Jonathan R Goodman
 
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  • #21
PeroK
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The delta (B.1.617.2) variant has an advantage over the alpha (B.1.1.7) variant in the UK. Secondary attack rates for delta are approximately 1.5 times those for alpha. Part of it is likely due to vaccine being less effective against delta than against alpha. First dose effectiveness for symptomatic disease is approximately 33% against delta, and 51% against alpha. Second dose effectiveness for delta and alpha are 88% and 93% respectively with the Pfizer vaccine; 60% and 66% respectively with AstraZeneca. (See @Ygggdrasil's post #2)

This interesting article by points out that because the UK used such a long interval between first and second doses, the difference in first dose effectiveness might have made a significant contribution to delta's advantage over alpha:
https://theconversation.com/covid-d...a-variant-an-evolutionary-helping-hand-162359
COVID: did a delayed second dose give the delta variant an evolutionary helping hand?
Jonathan R Goodman
I'd like to see the figures on how many of the recent COVID cases have been among people vaccinated only once. Until you see those figures, the conclusion of this piece is too woolly, IMO.

In any case, you'd really need a full mathematical model for the spread of the Alpha and Delta variants under the different vaccination policies. Otherwise, there is no way to quantify the evolutionary advantage. It might be negligible when you run the model.
 
  • #22
atyy
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I'd like to see the figures on how many of the recent COVID cases have been among people vaccinated only once. Until you see those figures, the conclusion of this piece is too woolly, IMO.

In any case, you'd really need a full mathematical model for the spread of the Alpha and Delta variants under the different vaccination policies. Otherwise, there is no way to quantify the evolutionary advantage. It might be negligible when you run the model.
Of course it's not a conclusion, just pointing out that while delta might be more transmissible, the degree to which it is more transmissible has not yet been quantified properly, with proper consideration of the effects of vaccination, so it may be quite a bit less than the 1.4 or 1.5 times advantage suggested by the raw secondary attack numbers.
 
  • #23
PeroK
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Of course it's not a conclusion, just pointing out that while delta might be more transmissible, the degree to which it is more transmissible has not yet been quantified properly, with proper consideration of the effects of vaccination, so it may be quite a bit less than the 1.4 or 1.5 times advantage suggested by the raw secondary attack numbers.
Yes, but I'd like to see some numbers!

For example, at the end of March we had 26.5 million people vaccinated only once, and 4.5 million twice. The alternative (given we'd done 7.5 million vaccinations in the previous two weeks) would have been approx: 3.5 million people only once and 16 million twice.

Crudely, at the end of March:

For Alpha we had 31 million people protected and 23 million (plus 14 million children) vulnerable.

For Delta we had only 4.5 million people protected.

Alternatively, we could have had:

For Alpha 19.5 milion people protected.

For Delta 16 million people protected.

It's all very plausible. but without those numbers the article seems a bit short on data to me.
 
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  • #24
atyy
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Maybe the May numbers are more relevant, since that's when delta started increasing in the UK?

BTW, the article is not criticizing the decision to lengthen the time between doses.
 
  • #25
PeroK
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Maybe the May numbers are more relevant, since that's when delta started increasing in the UK?

BTW, the article is not criticizing the decision to lengthen the time between doses.
I had to fix the numbers above. I forgot that only half of the recent jabs would be first timers.

By the end of April the numbers were:

For Alpha: 34.5 million protected (at least once)

For Delta: 15 million protected (twice)

And we could have had:

For Alpha: 26.5 million protected (at least once)

For Delta: 23 million protected (twice).
 
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