19 ms·

Delaying a Covid vaccine’s second dose boosts immune response

312 points by throwkeep 5y ago

Animats 5y ago
This suggests a third booster shot may be useful for some people. That will probably be tested. Good to have such an option, if needed.
- aledalgrande 5y ago
  Booster shots are already getting ordered. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-new-supply-agreement-switzerland-7-million https://investors.modernatx.com/news-releases/news-release-d...
  - standardUser 5y ago
    It is currently not known if or when boosters may be needed.
    - fullstackchris 5y ago
      what planet are you on? there have already been multiple studies that show the efficiacy of existing vaccines are not as effective against some of the variants. don't doubt that there will be bootsters for this
      - Scoundreller 5y ago
        And we’ll probably have more mutants appear. We’re hitting all time records in new infections. The more infections, the more copies, the more risk of an imperfect replication (mutant) that’s worse. I’m happy that pigs and birds don’t seem to get COVID-19 (and hoping that’s not a mutation away).
      - standardUser 5y ago
        No variant has been shown to evade the leading vaccines to the point that they are not effective, and there has is no established timetable for when immunity form vaccines fades.
- nicoburns 5y ago
  Here in the UK the plan seems to be to provide a 3rd booster ina slightly tweaked form that better targets some of the new variants. I read that it could be available from as early as september.
- fatsdomino001 5y ago
  and a fourth booster... and a fifth... sixth, seventh, etc.
  - officialjunk 5y ago
    with the current formulas this is true. https://www.forbes.com/sites/williamhaseltine/2021/03/25/modeling-study-predicts-immune-protection-may-vary-for-different-covid-19-vaccines/ https://www.forbes.com/sites/williamhaseltine/2021/03/25/mod... seeing almost half the efficacy after 250 days.
  - aledalgrande 5y ago
    Which is going to be the future. The CEO of Moderna was talking about it. An annual shot that includes COVID, flu, cold and other vaccines. We'll get to a point in which we will look back at having a cold like you look at a Nokia 3310 now. Edit: podcast link for who's curious https://ark-invest.com/podcast/understanding-mrna-conversations-with-moderna-and-arcturus-therapeutics/ https://ark-invest.com/podcast/understanding-mrna-conversati...
    - osenthuortuh 5y ago
      I want to say something sarcastic, but I am in genuine disbelief that this could be anyone's vision for the future of humanity. What an abhorrent nightmare.
      - TchoBeer 5y ago
        I don't see why eliminating disease is an abhorrent nightmare to you. Is the fact that no one gets polio anymore also an abhorrent nightmare?
        at-fates-hands 5y ago
        Polio was never eliminated. It still persists in poor countries and among abject poverty stricken communities. Wild poliovirus has been eradicated in all continents except Asia, and as of 2020, Afghanistan and Pakistan are the only two countries where the disease is still classified as endemic.[5][6] https://en.wikipedia.org/wiki/Polio_eradication https://en.wikipedia.org/wiki/Polio_eradication
AS_of 5y ago
> For the United Kingdom, extending the interval between doses was clearly the right choice, but the country’s lockdown deserves part of the credit for that success This is important for anyone who thinks it might be a good idea to wait. You have to carefully weigh the risk of being vulnerable in the meantime.
- pityJuke 5y ago
  It isn't that simple though. The first dose still provides some protection. The choice is usually between a lot of people having some protection, vs a smaller amount of people having full protection. (and some protection can be in the 70% range [1]) [1]: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00790-X/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
  - rsj_hn 5y ago
    Yes, rather than "some", I would say that the first dose provides the majority of protection, and the second is a booster, upping the effectiveness from the 70s to the 90s. If you are short vaccine, it makes a lot of sense to give out only a single dose to more people than both doses to a smaller group of people and then circle back when more is produced. The only question is whether it makes sense to circle back if the time elapsed is long, and this study is evidence that it does.
- ddlutz 5y ago
  The vaccines are still quite effective after the first dose, and, I'm saying this without being a researcher in this area, should be enough to flatten the curve. "The Moderna vaccine has been shown to have an efficacy of approximately 92 per cent in protecting against COVID-19, starting 14 days after the first dose." - https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know https://www.who.int/news-room/feature-stories/detail/the-mod...
  - aledalgrande 5y ago
    Wow that's impressive, I thought it was ~50% after the first dose. I guess it's like ML, to get the last percentage points you need exponential effort?
heavymark 5y ago
…in those over 80… the study says for those only reading the title.
- sp3000 5y ago
  I agree that is an important point. While that was the population that was tested, I think it is OK to infer that there would be a similar response to those under 80 as well.
  - ipaddr 5y ago
    We can hope and guess it will work at the same rate but because the response to covid between the youngest and the oldest have been so different we would have to assume it's probably different to some degree.
- thepangolino 5y ago
  Those over 80 make up half of the covid death count. I'd say that's pretty encouraging.
  - sharken 5y ago
    India seems to be a special case, as only 4.8% of the population is above 65. https://www.sciencemag.org/news/2021/04/will-india-s-devastating-covid-19-surge-provide-data-clear-its-death-paradox https://www.sciencemag.org/news/2021/04/will-india-s-devasta... Apart from India it seems that Japan should take notes, it's quite a surprise to me that only 1% of the population has been fully vaccinated. No wonder they are reluctant to let spectators be present for the olympics. https://www.sciencemag.org/news/2021/05/only-1-japan-fully-vaccinated-against-covid-19-it-ready-olympics https://www.sciencemag.org/news/2021/05/only-1-japan-fully-v...
    - elif 5y ago
      I was just watching on NHK that the N501Y mutated strain in Japan is putting healthy 30-60 year olds in hospital care 66% more often. They are actively cancelling Olympic training events and reducing paralympic events, and only 10% of Tokyo residents surveyed said they are happy the games are going to continue as planned.
randcraw 5y ago
From the Nature article: "Peak antibody levels were 3.5 times higher in those who waited 12 weeks for their booster shot than were those in people who waited only 3 weeks. Peak T-cell response was lower in those with the extended interval. But this did not cause antibody levels to decline more quickly over the nine weeks after the booster shot." I care less about short-term peak antibody response than longer-term T-cell response or longest-term immunizing antibody response. On the latter two points, this study was not encouraging or outright silent. Nor was there any indication of how well these folks fared after they returned to the wild. This info doesn't seem sufficient to draw meaningful conclusions about longer term protection.
- hprotagonist 5y ago
  in particular, a linear change in antibody levels, which trigger an exponential response, doesn't really mean very much!
- wutbrodo 5y ago
  Some more info from the uni that performed the study[1]: > In relation to the cellular (or T cell) immune response, which plays an important role in supporting and maintaining antibody production, the team found that within the three-week interval group, 60% had a confirmed cellular response at two to three weeks following the second vaccine - although this fell to only 15% eight to nine weeks later. > The proportion of participants showing a cellular response in the 12-week-interval group was only eight per cent at five to six weeks after the first vaccine, but this rose to 31% two to three weeks after the second vaccine. Research is required to further explore these variations in responses. You're correct that the evidence isn't dispositive yet, but it's an encouraging signal. Antibody response in the short-term is positive and in the medium-term cellular response possibly converges. More importantly, the implications for the first doses first strategy are positive. Those who know how to reason under uncertainty saw the UK's strategy as a calculated gamble based on a model that extended the point information provided by the vaccine efficacy RCT; critics were generally incoherent but their claim was that it was likely to cause large _negative_ effects on efficacy, worth paying the cost of vaccinating far fewer people. On top of the priors that led to the decision, we now have signal from the way the winter surge played out in the UK, and the increased antibody response alone provides further weak signal that the delay was worth it - and conversely, that the US's approach cost lives). The evidence still isn't dispositive, but crucially, there's no such strong basis for believing the alternative either: that extending doses _reduces_ efficacy and that vaccine availability should be limited in the name of adhering rigidly to the RCT-studied timeline. The status quo bias of medical culture killed a lot of people during this pandemic by continuing their habit of pretending that certainty exists where none does and refusing to engage in critical thinking about uncertainty. Refusing to explicitly extrapolate a model from few high-quality samples really just means "implicitly extrapolating a crappy model through bias and guesswork". This may be adaptive in the normal medical context, where the status quo is generally fine, but is an incredibly poor fit for a fast-moving pandemic that was killing thousands a day in the US alone. [1] https://www.birmingham.ac.uk/news/latest/2021/05/covid-pfizer-vaccination-interval-antibody-response.aspx https://www.birmingham.ac.uk/news/latest/2021/05/covid-pfize...
TMWNN 5y ago
Does this mean that a one-shot vaccine like Johnson & Johnson's is inherently less effective?
- robbrown451 5y ago
  I suspect that it is. There may be some reason it is good enough with a single shot, but the others aren't, but still... I didn't want J&J, not because I think it is a worse vaccine, but because it is currently only a single shot.
- suyash 5y ago
  I think it only protects about 60-70%
- tgsovlerkhgsel 5y ago
  Is there any evidence one shot of J&J protects better than one shot of Moderna/Biontech, or is the main difference that the companies chose different strategies for their studies/marketing? (Moderna/Biontech hoping to achieve better results and 2x the doses sold, J&J hoping to be done with the studies 3-4 weeks earlier and having a marketing advantage because it only requires one shot)
- hammock 5y ago
  J&j could have been formulated as 2-dose, but they didn't test it that way, because the type of vaccine it is is well tested already to have reasonable effectiveness with a single dose. No rna jab had never passed phase iii before, so they hedged their bets and tested a 1/2 + 1 formula, knowing that it had higher likelihood to succeed testing.
Havoc 5y ago
Can't help but feel the UK had incredible luck on their side here. Being in the UK I'm thankful it played out well...but wow...talk about a roll of the dice. (As best as I know there was little scientific evidence available when they decided to delay)
- Hallucinaut 5y ago
  Depends what you mean by "little". At the start of the year, if not the end of 2020, there were studies showing the prevailing effectiveness with delays on the second shot so it was pretty clear where the trend was. And then, merely hours ago, they decided because of the Indian variant they'd instead change the recommendation from 12 weeks to 8. So, at least in my opinion, it's a bit of a random walk down statistics street.
- mohammad_ali85 5y ago
  You’re correct, no evidence at the time JCVI (joint committee for vaccination and immunisation) made the call. However the decision was made on best interests [1] from a public health perspective. Delaying to 12 weeks allowed absolute numbers of people to be immunised once and build up some immunity versus absolute numbers of people vaccinated twice and having higher number of vulnerable populations without any immunity. Of course, this wasn’t taking into the people who had had COVID-19 and had a level of immunity to the virus from exposure. [1] https://www.gov.uk/government/news/statement-from-the-uk-chief-medical-officers-on-the-prioritisation-of-first-doses-of-covid-19-vaccines https://www.gov.uk/government/news/statement-from-the-uk-chi...
  - Closi 5y ago
    > You’re correct, no evidence at the time JCVI (joint committee for vaccination and immunisation) made the call. This isn't true, the JCVI did have evidence. In fact their statement showing reasons behind the call said: "There is evidence that a longer interval between the first and second doses promotes a stronger immune response with the AstraZeneca vaccine." https://www.gov.uk/government/publications/prioritising-the-first-covid-19-vaccine-dose-jcvi-statement/optimising-the-covid-19-vaccination-programme-for-maximum-short-term-impact https://www.gov.uk/government/publications/prioritising-the-... (Statement first released on 31st of December 2021, only available via google archive https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjckJWdl8rwAhWrA2MBHWdoAvwQFnoECAcQAA&url=https%3A%2F%2Fwww.cas.mhra.gov.uk%2FViewandAcknowledgment%2FViewAttachment.aspx%3FAttachment_id%3D103741&usg=AOvVaw0WyPYOmGL3JNZoTvBi4q0P https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&c...)
josefresco 5y ago
Great. My local health clinic auto-booked my next appointment (despite telling me I had to do it) just inside 3 weeks from my first shot. I think they're a little worried about people coming back for their second shot.
suyash 5y ago
Good reason to delay one's second shot, I already pushed back by a week thinking of delaying even more.
hervature 5y ago
We'll soon find out from Canada what the effects of a 4 month gap does to response for all age groups.
- x86ARMsRace 5y ago
  As a Canadian (read: lab rat) I'm hoping this forced experiment I'm participating in, run by someone with no scientific background, ends well also. Thousands of lives are depending on what, at this point, amounts to a gamble on minimal evidence.
  - ahmedalsudani 5y ago
    There is plenty of evidence that the first shot reduces the risk of the worst symptoms quite significantly.
    - x86ARMsRace 5y ago
      > reduces the risk of the worst symptoms quite significantly. Right, reduces, but the full dose is needed to render the virus mostly harmless. My partner's coworker has Covid and one does of the vaccine, they are still severely ill.
      - pcbro141 5y ago
        Do you happen to know roughly how long after getting vaccinated they caught covid? It takes ~14 days after the first dose to get the ~80-90% protection (Pfizer/Moderna).
        __xyz 5y ago
        Unfortunately, I think this is not true for the latest mutations that appeared within the last months (e.g. B.1.1.7 from the UK). Please correct me in case you have different information
      - smnrchrds 5y ago
8bitsrule 5y ago
This story back in February reported 'Single Pfizer shot 90 percent effective after 21 days' and that 'vaccine effectiveness was still pretty much zero until about 14 days after people were vaccinated. But then after day 14 immunity rose gradually day by day to about 90 percent at day 21....' [https://medicalxpress.com/news/2021-02-pfizer-shot-percent-effective-days.html https://medicalxpress.com/news/2021-02-pfizer-shot-percent-e...] This looks to fit in with that trend ... after 14 days, slowly growing immunity.
belter 5y ago
I just had a conversation with a doctor. She mentioned her clinical team thinks that if you had COVID recently you should wait 3 to 4 months before getting vaccinated. The reason being because your immune system is messed up. Any doctors or immunologists here that can comment on this advice ?
AzzieElbab 5y ago
Wow Canada finally got something right by being a laggard
lobocinza 5y ago
I'm curious about non-mRNA vaccines like CoronaVac on Brazil where second dose shots are being delayed due to supply problems.

312 points by throwkeep 5y ago

This suggests a third booster shot may be useful for some people. That will probably be tested. Good to have such an option, if needed.

aledalgrande 5y ago
Booster shots are already getting ordered. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-new-supply-agreement-switzerland-7-million https://investors.modernatx.com/news-releases/news-release-d...
- standardUser 5y ago
  It is currently not known if or when boosters may be needed.
  - fullstackchris 5y ago
    what planet are you on? there have already been multiple studies that show the efficiacy of existing vaccines are not as effective against some of the variants. don't doubt that there will be bootsters for this
    - Scoundreller 5y ago
      And we’ll probably have more mutants appear. We’re hitting all time records in new infections. The more infections, the more copies, the more risk of an imperfect replication (mutant) that’s worse. I’m happy that pigs and birds don’t seem to get COVID-19 (and hoping that’s not a mutation away).
    - standardUser 5y ago
      No variant has been shown to evade the leading vaccines to the point that they are not effective, and there has is no established timetable for when immunity form vaccines fades.
nicoburns 5y ago
Here in the UK the plan seems to be to provide a 3rd booster ina slightly tweaked form that better targets some of the new variants. I read that it could be available from as early as september.
fatsdomino001 5y ago
and a fourth booster... and a fifth... sixth, seventh, etc.
- officialjunk 5y ago
  with the current formulas this is true. https://www.forbes.com/sites/williamhaseltine/2021/03/25/modeling-study-predicts-immune-protection-may-vary-for-different-covid-19-vaccines/ https://www.forbes.com/sites/williamhaseltine/2021/03/25/mod... seeing almost half the efficacy after 250 days.
- aledalgrande 5y ago
  Which is going to be the future. The CEO of Moderna was talking about it. An annual shot that includes COVID, flu, cold and other vaccines. We'll get to a point in which we will look back at having a cold like you look at a Nokia 3310 now. Edit: podcast link for who's curious https://ark-invest.com/podcast/understanding-mrna-conversations-with-moderna-and-arcturus-therapeutics/ https://ark-invest.com/podcast/understanding-mrna-conversati...
  - osenthuortuh 5y ago
    I want to say something sarcastic, but I am in genuine disbelief that this could be anyone's vision for the future of humanity. What an abhorrent nightmare.
    - TchoBeer 5y ago
      I don't see why eliminating disease is an abhorrent nightmare to you. Is the fact that no one gets polio anymore also an abhorrent nightmare?
      - at-fates-hands 5y ago
        Polio was never eliminated. It still persists in poor countries and among abject poverty stricken communities. Wild poliovirus has been eradicated in all continents except Asia, and as of 2020, Afghanistan and Pakistan are the only two countries where the disease is still classified as endemic.[5][6] https://en.wikipedia.org/wiki/Polio_eradication https://en.wikipedia.org/wiki/Polio_eradication

AS_of 5y ago

> For the United Kingdom, extending the interval between doses was clearly the right choice, but the country’s lockdown deserves part of the credit for that success This is important for anyone who thinks it might be a good idea to wait. You have to carefully weigh the risk of being vulnerable in the meantime.

pityJuke 5y ago
It isn't that simple though. The first dose still provides some protection. The choice is usually between a lot of people having some protection, vs a smaller amount of people having full protection. (and some protection can be in the 70% range [1]) [1]: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00790-X/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
- rsj_hn 5y ago
  Yes, rather than "some", I would say that the first dose provides the majority of protection, and the second is a booster, upping the effectiveness from the 70s to the 90s. If you are short vaccine, it makes a lot of sense to give out only a single dose to more people than both doses to a smaller group of people and then circle back when more is produced. The only question is whether it makes sense to circle back if the time elapsed is long, and this study is evidence that it does.
ddlutz 5y ago
The vaccines are still quite effective after the first dose, and, I'm saying this without being a researcher in this area, should be enough to flatten the curve. "The Moderna vaccine has been shown to have an efficacy of approximately 92 per cent in protecting against COVID-19, starting 14 days after the first dose." - https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know https://www.who.int/news-room/feature-stories/detail/the-mod...
- aledalgrande 5y ago
  Wow that's impressive, I thought it was ~50% after the first dose. I guess it's like ML, to get the last percentage points you need exponential effort?

heavymark 5y ago

…in those over 80… the study says for those only reading the title.

sp3000 5y ago
I agree that is an important point. While that was the population that was tested, I think it is OK to infer that there would be a similar response to those under 80 as well.
- ipaddr 5y ago
  We can hope and guess it will work at the same rate but because the response to covid between the youngest and the oldest have been so different we would have to assume it's probably different to some degree.
thepangolino 5y ago
Those over 80 make up half of the covid death count. I'd say that's pretty encouraging.
- sharken 5y ago
  India seems to be a special case, as only 4.8% of the population is above 65. https://www.sciencemag.org/news/2021/04/will-india-s-devastating-covid-19-surge-provide-data-clear-its-death-paradox https://www.sciencemag.org/news/2021/04/will-india-s-devasta... Apart from India it seems that Japan should take notes, it's quite a surprise to me that only 1% of the population has been fully vaccinated. No wonder they are reluctant to let spectators be present for the olympics. https://www.sciencemag.org/news/2021/05/only-1-japan-fully-vaccinated-against-covid-19-it-ready-olympics https://www.sciencemag.org/news/2021/05/only-1-japan-fully-v...
  - elif 5y ago
    I was just watching on NHK that the N501Y mutated strain in Japan is putting healthy 30-60 year olds in hospital care 66% more often. They are actively cancelling Olympic training events and reducing paralympic events, and only 10% of Tokyo residents surveyed said they are happy the games are going to continue as planned.

randcraw 5y ago

From the Nature article: "Peak antibody levels were 3.5 times higher in those who waited 12 weeks for their booster shot than were those in people who waited only 3 weeks. Peak T-cell response was lower in those with the extended interval. But this did not cause antibody levels to decline more quickly over the nine weeks after the booster shot." I care less about short-term peak antibody response than longer-term T-cell response or longest-term immunizing antibody response. On the latter two points, this study was not encouraging or outright silent. Nor was there any indication of how well these folks fared after they returned to the wild. This info doesn't seem sufficient to draw meaningful conclusions about longer term protection.

hprotagonist 5y ago
in particular, a linear change in antibody levels, which trigger an exponential response, doesn't really mean very much!
wutbrodo 5y ago
Some more info from the uni that performed the study[1]: > In relation to the cellular (or T cell) immune response, which plays an important role in supporting and maintaining antibody production, the team found that within the three-week interval group, 60% had a confirmed cellular response at two to three weeks following the second vaccine - although this fell to only 15% eight to nine weeks later. > The proportion of participants showing a cellular response in the 12-week-interval group was only eight per cent at five to six weeks after the first vaccine, but this rose to 31% two to three weeks after the second vaccine. Research is required to further explore these variations in responses. You're correct that the evidence isn't dispositive yet, but it's an encouraging signal. Antibody response in the short-term is positive and in the medium-term cellular response possibly converges. More importantly, the implications for the first doses first strategy are positive. Those who know how to reason under uncertainty saw the UK's strategy as a calculated gamble based on a model that extended the point information provided by the vaccine efficacy RCT; critics were generally incoherent but their claim was that it was likely to cause large _negative_ effects on efficacy, worth paying the cost of vaccinating far fewer people. On top of the priors that led to the decision, we now have signal from the way the winter surge played out in the UK, and the increased antibody response alone provides further weak signal that the delay was worth it - and conversely, that the US's approach cost lives). The evidence still isn't dispositive, but crucially, there's no such strong basis for believing the alternative either: that extending doses _reduces_ efficacy and that vaccine availability should be limited in the name of adhering rigidly to the RCT-studied timeline. The status quo bias of medical culture killed a lot of people during this pandemic by continuing their habit of pretending that certainty exists where none does and refusing to engage in critical thinking about uncertainty. Refusing to explicitly extrapolate a model from few high-quality samples really just means "implicitly extrapolating a crappy model through bias and guesswork". This may be adaptive in the normal medical context, where the status quo is generally fine, but is an incredibly poor fit for a fast-moving pandemic that was killing thousands a day in the US alone. [1] https://www.birmingham.ac.uk/news/latest/2021/05/covid-pfizer-vaccination-interval-antibody-response.aspx https://www.birmingham.ac.uk/news/latest/2021/05/covid-pfize...

TMWNN 5y ago

Does this mean that a one-shot vaccine like Johnson & Johnson's is inherently less effective?

robbrown451 5y ago
I suspect that it is. There may be some reason it is good enough with a single shot, but the others aren't, but still... I didn't want J&J, not because I think it is a worse vaccine, but because it is currently only a single shot.
suyash 5y ago
I think it only protects about 60-70%
tgsovlerkhgsel 5y ago
Is there any evidence one shot of J&J protects better than one shot of Moderna/Biontech, or is the main difference that the companies chose different strategies for their studies/marketing? (Moderna/Biontech hoping to achieve better results and 2x the doses sold, J&J hoping to be done with the studies 3-4 weeks earlier and having a marketing advantage because it only requires one shot)
hammock 5y ago
J&j could have been formulated as 2-dose, but they didn't test it that way, because the type of vaccine it is is well tested already to have reasonable effectiveness with a single dose. No rna jab had never passed phase iii before, so they hedged their bets and tested a 1/2 + 1 formula, knowing that it had higher likelihood to succeed testing.

Havoc 5y ago

Can't help but feel the UK had incredible luck on their side here. Being in the UK I'm thankful it played out well...but wow...talk about a roll of the dice. (As best as I know there was little scientific evidence available when they decided to delay)

Hallucinaut 5y ago
Depends what you mean by "little". At the start of the year, if not the end of 2020, there were studies showing the prevailing effectiveness with delays on the second shot so it was pretty clear where the trend was. And then, merely hours ago, they decided because of the Indian variant they'd instead change the recommendation from 12 weeks to 8. So, at least in my opinion, it's a bit of a random walk down statistics street.
mohammad_ali85 5y ago
You’re correct, no evidence at the time JCVI (joint committee for vaccination and immunisation) made the call. However the decision was made on best interests [1] from a public health perspective. Delaying to 12 weeks allowed absolute numbers of people to be immunised once and build up some immunity versus absolute numbers of people vaccinated twice and having higher number of vulnerable populations without any immunity. Of course, this wasn’t taking into the people who had had COVID-19 and had a level of immunity to the virus from exposure. [1] https://www.gov.uk/government/news/statement-from-the-uk-chief-medical-officers-on-the-prioritisation-of-first-doses-of-covid-19-vaccines https://www.gov.uk/government/news/statement-from-the-uk-chi...
- Closi 5y ago
  > You’re correct, no evidence at the time JCVI (joint committee for vaccination and immunisation) made the call. This isn't true, the JCVI did have evidence. In fact their statement showing reasons behind the call said: "There is evidence that a longer interval between the first and second doses promotes a stronger immune response with the AstraZeneca vaccine." https://www.gov.uk/government/publications/prioritising-the-first-covid-19-vaccine-dose-jcvi-statement/optimising-the-covid-19-vaccination-programme-for-maximum-short-term-impact https://www.gov.uk/government/publications/prioritising-the-... (Statement first released on 31st of December 2021, only available via google archive https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjckJWdl8rwAhWrA2MBHWdoAvwQFnoECAcQAA&url=https%3A%2F%2Fwww.cas.mhra.gov.uk%2FViewandAcknowledgment%2FViewAttachment.aspx%3FAttachment_id%3D103741&usg=AOvVaw0WyPYOmGL3JNZoTvBi4q0P https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&c...)

josefresco 5y ago

Great. My local health clinic auto-booked my next appointment (despite telling me I had to do it) just inside 3 weeks from my first shot. I think they're a little worried about people coming back for their second shot.

suyash 5y ago

Good reason to delay one's second shot, I already pushed back by a week thinking of delaying even more.

hervature 5y ago

We'll soon find out from Canada what the effects of a 4 month gap does to response for all age groups.

x86ARMsRace 5y ago
As a Canadian (read: lab rat) I'm hoping this forced experiment I'm participating in, run by someone with no scientific background, ends well also. Thousands of lives are depending on what, at this point, amounts to a gamble on minimal evidence.
- ahmedalsudani 5y ago
  There is plenty of evidence that the first shot reduces the risk of the worst symptoms quite significantly.
  - x86ARMsRace 5y ago
    > reduces the risk of the worst symptoms quite significantly. Right, reduces, but the full dose is needed to render the virus mostly harmless. My partner's coworker has Covid and one does of the vaccine, they are still severely ill.
    - pcbro141 5y ago
      Do you happen to know roughly how long after getting vaccinated they caught covid? It takes ~14 days after the first dose to get the ~80-90% protection (Pfizer/Moderna).
      - __xyz 5y ago
        Unfortunately, I think this is not true for the latest mutations that appeared within the last months (e.g. B.1.1.7 from the UK). Please correct me in case you have different information
    - smnrchrds 5y ago

8bitsrule 5y ago

This story back in February reported 'Single Pfizer shot 90 percent effective after 21 days' and that 'vaccine effectiveness was still pretty much zero until about 14 days after people were vaccinated. But then after day 14 immunity rose gradually day by day to about 90 percent at day 21....' [https://medicalxpress.com/news/2021-02-pfizer-shot-percent-effective-days.html https://medicalxpress.com/news/2021-02-pfizer-shot-percent-e...] This looks to fit in with that trend ... after 14 days, slowly growing immunity.

belter 5y ago

I just had a conversation with a doctor. She mentioned her clinical team thinks that if you had COVID recently you should wait 3 to 4 months before getting vaccinated. The reason being because your immune system is messed up. Any doctors or immunologists here that can comment on this advice ?

AzzieElbab 5y ago

Wow Canada finally got something right by being a laggard

lobocinza 5y ago

I'm curious about non-mRNA vaccines like CoronaVac on Brazil where second dose shots are being delayed due to supply problems.