7 ms·

Sinovac's vaccine efficacy less than 60% in Brazil trial -report

130 points by drocer88 6y ago

Proven 6y ago
But it's cheaper. You can buy two for the price of one Pfizer vaccine and get ahead that way. 20% gain.
neves 6y ago
Brazil is in a mess. The vaccine has been politicized, and our president is a crazy antivaxer. Butantan is a serious research center, but the lack of transparency is really troubling.
threeseed 6y ago
Sounds like these countries are better off waiting for the AstreZeneca vaccine. Which is affordable and far more effective.
- votepaunchy 6y ago
  AstreZeneca showed 70% efficacy in the general population. Does this qualify as “far more effective” when the mRNA vaccines showed 95% efficacy?
  - jimmydorry 6y ago
    The pfizer vaccine looks to be sitting closer to 30%[1] than 95% based on the parts of their trial data they are choosing to release. >With 20 times more suspected than confirmed cases, this category of disease cannot be ignored simply because there was no positive PCR test result. Indeed this makes it all the more urgent to understand. A rough estimate of vaccine efficacy against developing covid-19 symptoms, with or without a positive PCR test result, would be a relative risk reduction of 19% (see footnote)—far below the 50% effectiveness threshold for authorization set by regulators. [1] https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-modernas-95-effective-vaccines-we-need-more-details-and-the-raw-data/ https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-...
    - sterlind 6y ago
      > Even after removing cases occurring within 7 days of vaccination (409 on Pfizer’s vaccine vs. 287 on placebo), which should include the majority of symptoms due to short-term vaccine reactogenicity, vaccine efficacy remains low: 29% (see footnote). The 95% claim assumes you've had both doses and five weeks have passed since the first dose. I don't think that's a fair way to dice the data. Also, "covid-19 symptoms" (the proxy that opinion writer used) are very non-specific. Headache, sore throat, cough - there's myriad causes. That's why PCR+ is the only way to get a decent signal. This seems like a crackpot analysis, not that I'm an expert. Oh, and finally, relative risk reduction (that number you're quoting) is a fundamentally different property than efficacy. It's the difference between the placebo and vaccine groups in catching covid. Relative risk reduction would only equal efficacy if 100% of the placebo group caught it.
      - jimmydorry 6y ago
        Not everything you disagree with is a crackpot analysis. >The BMJ is a weekly peer-reviewed medical trade journal, published by the trade union the British Medical Association (BMA). The BMJ has editorial freedom from the BMA. It is one of the world's oldest general medical journals. [1] >Peter Doshi is an associate editor at said journal. He completed a fellowship in comparative effectiveness research at Johns Hopkins and received his Ph.D. in history, anthropology, and science, technology and society from the Massachusetts Institute of Technology. [2] I could not quote the entire article, but as we all know, failing to quote any of it usually ends up with a majority not being aware of any content within the article. The key finding is that further investigation is required into the substantial portion of people with COVID-like symptoms that occured in both the experimental and placebo groups, which has not been adequately analyzed. The entire article addressed VE (measured by calculating the risk of disease among vaccinated and unvaccinated persons and determining the percentage reduction in risk of disease among vaccinated persons relative to unvaccinated persons) and showed the raw numbers which allows anyone else to reach the same calculation result. [1] https://en.wikipedia.org/wiki/The_BMJ https://en.wikipedia.org/wiki/The_BMJ [2] https://www.bmj.com/about-bmj/editorial-staff/peter-doshi https://www.bmj.com/about-bmj/editorial-staff/peter-doshi
  - garmaine 6y ago
    Yes, actually. That’s right at the inflection point where each added percent effectiveness is maximally beneficial to herd immunity. E.g. the difference from 85% to 95% is much less important than 60% -> 70%.
    - mlyle 6y ago
      ?? This is a crazy way to look at it. If R0 is 2.5, then you need to vaccinate (1 - 1/2.5) / .95 of the population = 63% to reach herd immunity. For a 60% effective vaccine, you get (1 - 1/2.5) / .6 = 100% of the population. Yes, the slope is slightly different but the rolloff is exceptionally gentle. There is a huge difference in practicality between even an 85% and 95% effective vaccine (70% of the population vs. 63% of the population). Not to mention that none of what we've measured is differences in transmissibility; it's quite possible that a 70% effective-against-symptomatic-illness vaccine only mitigates transmission rates by 35%, and thus can't reach herd immunity at any level of vaccination.
      - thesz 6y ago
        And for 50% effective vaccine and R0 of 2.5, one has to vaccinate what, (1-1/2.5)/0.5=1.2 or 120% of population? Please, correct your math. It is weirdly off.
        sanxiyn 6y ago
        50% effective vaccine could lower R0 of 2.5 to 1.25 (2.5 * 50% = 1.25). That's R0 > 1, so it can't stop transmission.
        clausz 6y ago
        No, it's not. It only means that with these given numbers it is impossible to reach herd immunity.
        garmaine 6y ago
        Not impossible, just can't be done by vaccination alone. The remaining required percentage of the population would have to get immunity from getting sick. This is what I was getting at in the grandparent post. 50% -> 60% and 85% -> 95% might both seem like they protect 10% more of the population, but the qualitative effect on the spread of the pandemic and be quite different. 60% might be enough to get herd immunity (with masks and social distancing), while 50% is not. Both 85% and 95% are definitely enough to get herd immunity, so to some extent that added protection matters less.
  - ulfw 6y ago
    It didn't show that. It showed 62%. 70% is a pooled result when you put the (too few) people into the calculation who got 90% efficacy, which scientists can't explain as that testing regimen was completely fucked up by Jenner and AZN (different dosage, different timing, different age group <55yr only). So it's hard to tell if it's really 90% (due to sample size) or WHY it might be more effective than the 62% number. The approvals so far for the AZN/Oxford vaccine have been for the full-full dose regimen, which has shown to be 62% effective only.
- tjpnz 6y ago
  Efficacy aside there's already some data suggesting challenges in getting people to accept the Sinovac vaccine to begin with: https://www.japantimes.co.jp/news/2020/12/29/asia-pacific/china-coronavirus-vaccines-trust/ https://www.japantimes.co.jp/news/2020/12/29/asia-pacific/ch...
superkuh 6y ago
60% is pretty good for an inactivated full virus vaccine. That's about what the trivalent seasonal influenza vaccines (using the same general technique) achieve.
- gruez 6y ago
  >That's about what the trivalent seasonal influenza vaccines (using the same general technique) achieve. Doesn't the seasonal flu vaccine also have the issue that they have to "predict" what strains would be active? Is that already factored into the effectiveness rate?
  - sanxiyn 6y ago
    Yes it is already factored in. Influenza vaccine efficacy is usually calculated separately for "matched" influenza and all influenza. 60% range is for matched.
- ulfw 6y ago
  Why the constant "flu" comparisons? It's a different virus.
  - rimliu 6y ago
    Besides that other comments said: we cannot compare to other coronaviruses, because we do not have vaccine for a common cold.
  - slaw 6y ago
    Both are respiratory diseases with similar symptoms. Most of the times you need laboratory test to confirm which one you have.
  - dehrmann 6y ago
    In this case, part of it was because the vaccines are "...using the same general technique," so it's comparing the vaccines more than the viruses.
- dehrmann 6y ago
sudosysgen 6y ago
Can we please mention that this is not an official result? Less than reputable brazilian news have come up with wildly different numbers, from 40% to 63.75% to 80%. This is incredibly unreliable. How about not writing articles about rumors from Brazilian Yahoo News? Least of all, reports that have been dismissed by the actual institute doing the trials.
- dmix 6y ago
  Deleted
  - sudosysgen 6y ago
    I think you might have replied to the wrong comment.
- speeder 6y ago
  I am Brazillian. People are not trusting anything regarding this... 1. Instituto Butantã, claims they can't publish the results of the trial because of NDA with Sinovac, and won't comment about the effectiveness. 2. Meanwhile Sinovac is being tried for corruption in China, and their defense was actually confirm they paid bribes to officials in various countries to approve their vaccines (not Coronavirus ones, the trial is about 2011 stuff), but claim that the officials (including Instituto Butantã related officials) that used extortion, and thus they are victims, not perpetrators of the crime. In this situation, when allegedly bribery is afoot, do you really think we should blindly trust the alleged criminals numbers?
  - nedp 6y ago
    > Meanwhile Sinovac is being tried for corruption in China, and their defense was actually confirm they paid bribes to officials in various countries to approve their vaccines (not Coronavirus ones, the trial is about 2011 stuff), but claim that the officials (including Instituto Butantã related officials) that used extortion, and thus they are victims, not perpetrators of the crime. Where can I read about this? Would like to know more about it since the National Government here in the Philippines will use the one created by Sinovac for vaccination and they're trying their best to convince people despite the public skepticism regarding the lower efficacy rates which seems to indicate what you've said.
jbm 6y ago
There was a thread about this with a fairly convincing rationale for misunderstandings about the effectiveness of Sinovac. (I'm not the commentator, but it seems detailed enough to be plausible) https://www.reddit.com/r/COVID19/comments/kt076p/butantan_vaccine_reaches_100_effectiveness_for/gikh7ef/?utm_source=reddit&utm_medium=web2x&context=3 https://www.reddit.com/r/COVID19/comments/kt076p/butantan_va...
3ace 6y ago
In Indonesia, the trial result reported a 65.3% efficacy https://jakartaglobe.id/news/indonesia-approves-sinovac-vaccine-amid-dramatic-surge-in-coronavirus-cases https://jakartaglobe.id/news/indonesia-approves-sinovac-vacc...
xeromal 6y ago
Does anyone know if you keep giving the vaccine to the person after it fails, its effectiveness could eventually trend up to 90+%?
- dehrmann 6y ago
  Not sure why you're being downvoted. We give multi-dose vaccinations all the time.
- kolinko 6y ago
  It might work the other way - the immune system may get used to a given virus and begin ignoring it. This is the way anti-allergy therapies work - you inject patients with a progressively higher amounts of the substance the person is used to and the immune system stops responding to it. With vaccines, there have been cases of this effect (found during testing, and not with covid vaccines so far).
- JonoW 6y ago
  Yeah not sure why this is downvoted, seems a fair question.
xbmcuser 6y ago
Is this for the 1st shot only before the booster is administered as if recall correctly for the other vaccines it was around 75-80% for the first shot and went to 95%+ after the 2nd shot. Even if it reaches 75-80% after the 2nd shot it is actually good enough and that was the figure most of the medical professionals were hoping and expecting before the 90-95% effective vaccines came out.
- sanxiyn 6y ago
  This is after two shots.
ulfw 6y ago
So far we heard 91% (Turkey), <60% (Brazil), 78% against mild cases (Brazil), 65% (Indonesia). So... what is it really?
- dicomdan 6y ago
  ;)
- dmix 6y ago
  Turkey claimed 90%+ but the numbers in their tests were tiny: > The Turkish trial data for CoronaVac is based on analysis of 1,322 participants which included 29 infected people, and efficacy evaluations were made 14 days after the second dose was administered. Plus I’m not sure comparing countries at that level is a good base line. There could be major demographic (vitamin D which has been shown to play a role has also been shown to be less prevalent in darker skin) and even the details of the trials (Turkeys itself usinf relatively small samples). Or even the quality of the healthcare system treating these people after they get sick. From the same article: > Experts say it’s not unusual for a vaccine to show different efficacy rates in various settings, as trial protocols, data size and population could impact results, but the way CoronaVac data has been released created some confusion. https://www.reuters.com/article/us-health-coronavirus-sinovac-idUSKBN2920QQ https://www.reuters.com/article/us-health-coronavirus-sinova... This leads to the same conclusion that we need to wait for more and better data. But also recognize all data isn’t equal when we do get it.
  - sanxiyn 6y ago
    Brazilian trial had 13,060 participants. (Source: https://clinicaltrials.gov/ct2/show/NCT04456595 https://clinicaltrials.gov/ct2/show/NCT04456595) So publication of Brazilian trial data mostly should settle the matter.
raverbashing 6y ago
Well, besides the numbers being hearsay, this refers to "full efficiency" which is pretty much a meaningless number in this case. It refers to the number of people who had any kind of symptom manifestation Now do you care that instead of dying you got a runny nose? It's a useful number for statistic purposes, not practical ones
- cm2187 6y ago
  You do if it is about whether it stops spreading the virus or not
  - raverbashing 6y ago
    Correct, you do care about sterilizing immunity, but you need to do PCR tests on everybody, I'm not sure it was the case there. That is not what this number is referring to though.
roel_v 6y ago
Does anyone know of a good resource that explains what 'efficacy' means for a vaccine, and what can (and cannot) be extrapolated from it? The reported efficacies are (from what I understand) 1 - (n infections in experimental group / n infections in control group). But then I see people draw wildly varying conclusiona from that, most of which I suspect are wrong (e.g. the relationship between 'efficacy rate' and 'group immunity' after everyone is vaccinated). But despite looking long and hard, I can't anyone explaining in detail what such efficacy rates mean (and don't mean).
- tallanvor 6y ago
  I may screw this up, but efficacy describes how effective the vaccine was in the trial vs the control group. So if each group had an equal number of people, and 100 people in the control group got sick, but only 5 people who received the vaccine group got sick, the efficacy rate would be 95%. The hope, of course, is that the vaccine's effectiveness (how well it does at preventing covid) is close to the efficacy, but it's very hard to know for sure. That's why it's best to have the trials spread out among demographics and even locations, to better try and identify what may cause the vaccine to be more or less effective.
- radu_floricica 6y ago
  Very good point. I read recently that there were no hospitalizations in the AstraZeneca vaccinated group, so by this metric it's 100% efficient. I really want to hear those numbers as well, it makes a huge difference in the decision to promote a certain vaccine.
- gandalfgreybeer 6y ago
  I think this is a straightforward resource for explaining it. https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html
bluenose69 6y ago
The first sentence of the article ends with "citing two people who seen the results." How does such a glaring grammatical error get past Reuters editors?

130 points by drocer88 6y ago

But it's cheaper. You can buy two for the price of one Pfizer vaccine and get ahead that way. 20% gain.

Brazil is in a mess. The vaccine has been politicized, and our president is a crazy antivaxer. Butantan is a serious research center, but the lack of transparency is really troubling.

threeseed 6y ago

Sounds like these countries are better off waiting for the AstreZeneca vaccine. Which is affordable and far more effective.

votepaunchy 6y ago
AstreZeneca showed 70% efficacy in the general population. Does this qualify as “far more effective” when the mRNA vaccines showed 95% efficacy?
- jimmydorry 6y ago
  The pfizer vaccine looks to be sitting closer to 30%[1] than 95% based on the parts of their trial data they are choosing to release. >With 20 times more suspected than confirmed cases, this category of disease cannot be ignored simply because there was no positive PCR test result. Indeed this makes it all the more urgent to understand. A rough estimate of vaccine efficacy against developing covid-19 symptoms, with or without a positive PCR test result, would be a relative risk reduction of 19% (see footnote)—far below the 50% effectiveness threshold for authorization set by regulators. [1] https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-modernas-95-effective-vaccines-we-need-more-details-and-the-raw-data/ https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-...
  - sterlind 6y ago
    > Even after removing cases occurring within 7 days of vaccination (409 on Pfizer’s vaccine vs. 287 on placebo), which should include the majority of symptoms due to short-term vaccine reactogenicity, vaccine efficacy remains low: 29% (see footnote). The 95% claim assumes you've had both doses and five weeks have passed since the first dose. I don't think that's a fair way to dice the data. Also, "covid-19 symptoms" (the proxy that opinion writer used) are very non-specific. Headache, sore throat, cough - there's myriad causes. That's why PCR+ is the only way to get a decent signal. This seems like a crackpot analysis, not that I'm an expert. Oh, and finally, relative risk reduction (that number you're quoting) is a fundamentally different property than efficacy. It's the difference between the placebo and vaccine groups in catching covid. Relative risk reduction would only equal efficacy if 100% of the placebo group caught it.
    - jimmydorry 6y ago
      Not everything you disagree with is a crackpot analysis. >The BMJ is a weekly peer-reviewed medical trade journal, published by the trade union the British Medical Association (BMA). The BMJ has editorial freedom from the BMA. It is one of the world's oldest general medical journals. [1] >Peter Doshi is an associate editor at said journal. He completed a fellowship in comparative effectiveness research at Johns Hopkins and received his Ph.D. in history, anthropology, and science, technology and society from the Massachusetts Institute of Technology. [2] I could not quote the entire article, but as we all know, failing to quote any of it usually ends up with a majority not being aware of any content within the article. The key finding is that further investigation is required into the substantial portion of people with COVID-like symptoms that occured in both the experimental and placebo groups, which has not been adequately analyzed. The entire article addressed VE (measured by calculating the risk of disease among vaccinated and unvaccinated persons and determining the percentage reduction in risk of disease among vaccinated persons relative to unvaccinated persons) and showed the raw numbers which allows anyone else to reach the same calculation result. [1] https://en.wikipedia.org/wiki/The_BMJ https://en.wikipedia.org/wiki/The_BMJ [2] https://www.bmj.com/about-bmj/editorial-staff/peter-doshi https://www.bmj.com/about-bmj/editorial-staff/peter-doshi
- garmaine 6y ago
  Yes, actually. That’s right at the inflection point where each added percent effectiveness is maximally beneficial to herd immunity. E.g. the difference from 85% to 95% is much less important than 60% -> 70%.
  - mlyle 6y ago
    ?? This is a crazy way to look at it. If R0 is 2.5, then you need to vaccinate (1 - 1/2.5) / .95 of the population = 63% to reach herd immunity. For a 60% effective vaccine, you get (1 - 1/2.5) / .6 = 100% of the population. Yes, the slope is slightly different but the rolloff is exceptionally gentle. There is a huge difference in practicality between even an 85% and 95% effective vaccine (70% of the population vs. 63% of the population). Not to mention that none of what we've measured is differences in transmissibility; it's quite possible that a 70% effective-against-symptomatic-illness vaccine only mitigates transmission rates by 35%, and thus can't reach herd immunity at any level of vaccination.
    - thesz 6y ago
      And for 50% effective vaccine and R0 of 2.5, one has to vaccinate what, (1-1/2.5)/0.5=1.2 or 120% of population? Please, correct your math. It is weirdly off.
      - sanxiyn 6y ago
        50% effective vaccine could lower R0 of 2.5 to 1.25 (2.5 * 50% = 1.25). That's R0 > 1, so it can't stop transmission.
      - clausz 6y ago
        No, it's not. It only means that with these given numbers it is impossible to reach herd immunity.
        garmaine 6y ago
        Not impossible, just can't be done by vaccination alone. The remaining required percentage of the population would have to get immunity from getting sick. This is what I was getting at in the grandparent post. 50% -> 60% and 85% -> 95% might both seem like they protect 10% more of the population, but the qualitative effect on the spread of the pandemic and be quite different. 60% might be enough to get herd immunity (with masks and social distancing), while 50% is not. Both 85% and 95% are definitely enough to get herd immunity, so to some extent that added protection matters less.
- ulfw 6y ago
  It didn't show that. It showed 62%. 70% is a pooled result when you put the (too few) people into the calculation who got 90% efficacy, which scientists can't explain as that testing regimen was completely fucked up by Jenner and AZN (different dosage, different timing, different age group <55yr only). So it's hard to tell if it's really 90% (due to sample size) or WHY it might be more effective than the 62% number. The approvals so far for the AZN/Oxford vaccine have been for the full-full dose regimen, which has shown to be 62% effective only.
tjpnz 6y ago
Efficacy aside there's already some data suggesting challenges in getting people to accept the Sinovac vaccine to begin with: https://www.japantimes.co.jp/news/2020/12/29/asia-pacific/china-coronavirus-vaccines-trust/ https://www.japantimes.co.jp/news/2020/12/29/asia-pacific/ch...

superkuh 6y ago

60% is pretty good for an inactivated full virus vaccine. That's about what the trivalent seasonal influenza vaccines (using the same general technique) achieve.

gruez 6y ago
>That's about what the trivalent seasonal influenza vaccines (using the same general technique) achieve. Doesn't the seasonal flu vaccine also have the issue that they have to "predict" what strains would be active? Is that already factored into the effectiveness rate?
- sanxiyn 6y ago
  Yes it is already factored in. Influenza vaccine efficacy is usually calculated separately for "matched" influenza and all influenza. 60% range is for matched.
ulfw 6y ago
Why the constant "flu" comparisons? It's a different virus.
- rimliu 6y ago
  Besides that other comments said: we cannot compare to other coronaviruses, because we do not have vaccine for a common cold.
- slaw 6y ago
  Both are respiratory diseases with similar symptoms. Most of the times you need laboratory test to confirm which one you have.
- dehrmann 6y ago
  In this case, part of it was because the vaccines are "...using the same general technique," so it's comparing the vaccines more than the viruses.
dehrmann 6y ago

sudosysgen 6y ago

Can we please mention that this is not an official result? Less than reputable brazilian news have come up with wildly different numbers, from 40% to 63.75% to 80%. This is incredibly unreliable. How about not writing articles about rumors from Brazilian Yahoo News? Least of all, reports that have been dismissed by the actual institute doing the trials.

dmix 6y ago
Deleted
- sudosysgen 6y ago
  I think you might have replied to the wrong comment.
speeder 6y ago
I am Brazillian. People are not trusting anything regarding this... 1. Instituto Butantã, claims they can't publish the results of the trial because of NDA with Sinovac, and won't comment about the effectiveness. 2. Meanwhile Sinovac is being tried for corruption in China, and their defense was actually confirm they paid bribes to officials in various countries to approve their vaccines (not Coronavirus ones, the trial is about 2011 stuff), but claim that the officials (including Instituto Butantã related officials) that used extortion, and thus they are victims, not perpetrators of the crime. In this situation, when allegedly bribery is afoot, do you really think we should blindly trust the alleged criminals numbers?
- nedp 6y ago
  > Meanwhile Sinovac is being tried for corruption in China, and their defense was actually confirm they paid bribes to officials in various countries to approve their vaccines (not Coronavirus ones, the trial is about 2011 stuff), but claim that the officials (including Instituto Butantã related officials) that used extortion, and thus they are victims, not perpetrators of the crime. Where can I read about this? Would like to know more about it since the National Government here in the Philippines will use the one created by Sinovac for vaccination and they're trying their best to convince people despite the public skepticism regarding the lower efficacy rates which seems to indicate what you've said.

jbm 6y ago

There was a thread about this with a fairly convincing rationale for misunderstandings about the effectiveness of Sinovac. (I'm not the commentator, but it seems detailed enough to be plausible) https://www.reddit.com/r/COVID19/comments/kt076p/butantan_vaccine_reaches_100_effectiveness_for/gikh7ef/?utm_source=reddit&utm_medium=web2x&context=3 https://www.reddit.com/r/COVID19/comments/kt076p/butantan_va...

3ace 6y ago

In Indonesia, the trial result reported a 65.3% efficacy https://jakartaglobe.id/news/indonesia-approves-sinovac-vaccine-amid-dramatic-surge-in-coronavirus-cases https://jakartaglobe.id/news/indonesia-approves-sinovac-vacc...

xeromal 6y ago

Does anyone know if you keep giving the vaccine to the person after it fails, its effectiveness could eventually trend up to 90+%?

dehrmann 6y ago
Not sure why you're being downvoted. We give multi-dose vaccinations all the time.
kolinko 6y ago
It might work the other way - the immune system may get used to a given virus and begin ignoring it. This is the way anti-allergy therapies work - you inject patients with a progressively higher amounts of the substance the person is used to and the immune system stops responding to it. With vaccines, there have been cases of this effect (found during testing, and not with covid vaccines so far).
JonoW 6y ago
Yeah not sure why this is downvoted, seems a fair question.

xbmcuser 6y ago

Is this for the 1st shot only before the booster is administered as if recall correctly for the other vaccines it was around 75-80% for the first shot and went to 95%+ after the 2nd shot. Even if it reaches 75-80% after the 2nd shot it is actually good enough and that was the figure most of the medical professionals were hoping and expecting before the 90-95% effective vaccines came out.

sanxiyn 6y ago
This is after two shots.

ulfw 6y ago

So far we heard 91% (Turkey), <60% (Brazil), 78% against mild cases (Brazil), 65% (Indonesia). So... what is it really?

dicomdan 6y ago
;)
dmix 6y ago
Turkey claimed 90%+ but the numbers in their tests were tiny: > The Turkish trial data for CoronaVac is based on analysis of 1,322 participants which included 29 infected people, and efficacy evaluations were made 14 days after the second dose was administered. Plus I’m not sure comparing countries at that level is a good base line. There could be major demographic (vitamin D which has been shown to play a role has also been shown to be less prevalent in darker skin) and even the details of the trials (Turkeys itself usinf relatively small samples). Or even the quality of the healthcare system treating these people after they get sick. From the same article: > Experts say it’s not unusual for a vaccine to show different efficacy rates in various settings, as trial protocols, data size and population could impact results, but the way CoronaVac data has been released created some confusion. https://www.reuters.com/article/us-health-coronavirus-sinovac-idUSKBN2920QQ https://www.reuters.com/article/us-health-coronavirus-sinova... This leads to the same conclusion that we need to wait for more and better data. But also recognize all data isn’t equal when we do get it.
- sanxiyn 6y ago
  Brazilian trial had 13,060 participants. (Source: https://clinicaltrials.gov/ct2/show/NCT04456595 https://clinicaltrials.gov/ct2/show/NCT04456595) So publication of Brazilian trial data mostly should settle the matter.

raverbashing 6y ago

Well, besides the numbers being hearsay, this refers to "full efficiency" which is pretty much a meaningless number in this case. It refers to the number of people who had any kind of symptom manifestation Now do you care that instead of dying you got a runny nose? It's a useful number for statistic purposes, not practical ones

cm2187 6y ago
You do if it is about whether it stops spreading the virus or not
- raverbashing 6y ago
  Correct, you do care about sterilizing immunity, but you need to do PCR tests on everybody, I'm not sure it was the case there. That is not what this number is referring to though.

roel_v 6y ago

Does anyone know of a good resource that explains what 'efficacy' means for a vaccine, and what can (and cannot) be extrapolated from it? The reported efficacies are (from what I understand) 1 - (n infections in experimental group / n infections in control group). But then I see people draw wildly varying conclusiona from that, most of which I suspect are wrong (e.g. the relationship between 'efficacy rate' and 'group immunity' after everyone is vaccinated). But despite looking long and hard, I can't anyone explaining in detail what such efficacy rates mean (and don't mean).

tallanvor 6y ago
I may screw this up, but efficacy describes how effective the vaccine was in the trial vs the control group. So if each group had an equal number of people, and 100 people in the control group got sick, but only 5 people who received the vaccine group got sick, the efficacy rate would be 95%. The hope, of course, is that the vaccine's effectiveness (how well it does at preventing covid) is close to the efficacy, but it's very hard to know for sure. That's why it's best to have the trials spread out among demographics and even locations, to better try and identify what may cause the vaccine to be more or less effective.
radu_floricica 6y ago
Very good point. I read recently that there were no hospitalizations in the AstraZeneca vaccinated group, so by this metric it's 100% efficient. I really want to hear those numbers as well, it makes a huge difference in the decision to promote a certain vaccine.
gandalfgreybeer 6y ago
I think this is a straightforward resource for explaining it. https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section6.html

bluenose69 6y ago

The first sentence of the article ends with "citing two people who seen the results." How does such a glaring grammatical error get past Reuters editors?