5 ms·

It's wild to me that in the trials they didn't test all participants (including asymptomatic people) when asymptomatic transmission is the reason we're in a pan

It's wild to me that in the trials they didn't test all participants (including asymptomatic people) when asymptomatic transmission is the reason we're in a pandemic.

SigmundA 6y ago
So have there ever been vaccines that prevent you from getting getting the disease while still allowing you to spread it? This is a genuine question.
- fossuser 6y ago
  I don't know - I'm also not the person that was arguing that. I have pretty high confidence that if you have the vaccine you won't transmit the disease - I suspect the scientists are just being overly cautious because they don't have the data yet (though it is now starting to prove this out). They don't have the data in part, because the trials did not test asymptomatic people. This means it's possible that some of the vaccinated people in the trial caught the virus, but at a reduced severity that was asymptomatic (but still transmissible). Pretend that the vaccine reduced severity, but most people still caught it and were just asymptomatic. In that world, the vaccine wouldn't be enough (and the trials would not have revealed this). Since we know that some people who get the vaccine do catch the virus, but just have a mild case - it seems like a plausible outcome that others catch it without symptoms, but can still transmit it. That said, it's looking like that's not the world we're in - and the vaccines do just stop you from contracting the disease in addition to reducing severity in the rare case you catch it anyway. mRNA vaccines are new and given the asymptomatic transmission of the virus is why we have a pandemic, it's a reasonable thing to be cautious about (which is why I was surprised the trials only tested symptomatic patients).
- sampo 6y ago
  > So have there ever been vaccines that prevent you from getting getting the disease while still allowing you to spread it? In chicken, Marek’s disease works like that. https://en.wikipedia.org/wiki/Marek%27s_disease#Prevention https://en.wikipedia.org/wiki/Marek%27s_disease#Prevention
- mLuby 6y ago
  According to this, most vaccines are as you describe: "There are two main types of immunity you can achieve with vaccines. One is so-called 'effective' immunity, which can prevent a pathogen from causing serious disease, but can't stop it from entering the body or making more copies of itself. The other is 'sterilising immunity', which can thwart infections entirely, and even prevent asymptomatic cases. The latter is the aspiration of all vaccine research, but *surprisingly rarely achieved*." https://www.bbc.com/future/article/20210203-why-vaccinated-people-may-still-be-able-to-spread-covid-19 Side note—I wonder if these scientists were inspired by Spider-Man (1962): "Nearly 40 years ago it was observed that sterilizing immunity against [Malaria] could be achieved by exposing human volunteers to the bites of irradiated mosquitoes carrying sporozoites in their salivary glands." https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sterilizing-immunity
- amluto 6y ago
  Polio. The injectable vaccine prevents nervous system damage. The oral vaccine prevents transmission too. The problem is that the oral vaccine is old technology and can revert to being dangerous. It’s rare but happens. So countries with resources gave everyone the IPV to protect them and then the OPV to eradicate the disease. Tetanus is a partial example, too. The tetanus vaccine protects against the tetanus toxin but has no particular effect on whether you can have the bacteria replicate in your body. But tetanus isn’t transmissible, so this doesn’t matter much.
maxerickson 6y ago
It'd be a logistical nightmare to setup validated testing and so on for tens of thousands of participants. The studies coming out that did regular testing focused on easily reached populations (medical workers) that may not have been representative of the wider population (so not suitable for the trials). https://www.nejm.org/doi/full/10.1056/NEJMc2102153 https://www.nejm.org/doi/full/10.1056/NEJMc2102153 https://www.nejm.org/doi/full/10.1056/NEJMc2101927 https://www.nejm.org/doi/full/10.1056/NEJMc2101927
- fossuser 6y ago
  Couldn't they have at least done the rapid antigen test when they came in for their second dose? Maybe I'm underestimating complexity (typical for an outsider), but just seemed surprising to me when I heard that.
  - sampo 6y ago
    Antigen test should show positive on vaccinated people.
- dcolkitt 6y ago
  Just collect data on the rate of infections of the members of the households of those in the study. Run an IV regression on the results. Since a significant fraction of transmission comes from those sharing a household, protection against asymptomatic transmission will show up in lower household infection rate among the vaccinated group.
  - maxerickson 6y ago
    Preventing severe infection is a fine endpoint though. A vaccine or treatment that does that is a minimum viable tool for moving forward. Reduces deaths, reduces utilization of medical resources, etc, and then when it's a vaccine, it's pretty likely that it also reduces transmission. But it doesn't need to reduce transmission to be worth an awful lot.
    - 6y ago
caddemon 6y ago
AFAIK the impact of asymptomatic transmission is still under debate. The bigger danger seems to be presymptomatic transmission. But my info may be a few months out of date, would be interested if anyone has any sources saying otherwise? Still though I agree it would have been useful to regularly test all trial participants - the US really could have done a lot better job with testing more generally.

It's wild to me that in the trials they didn't test all participants (including asymptomatic people) when asymptomatic transmission is the reason we're in a pandemic.

SigmundA 6y ago

So have there ever been vaccines that prevent you from getting getting the disease while still allowing you to spread it? This is a genuine question.

fossuser 6y ago
I don't know - I'm also not the person that was arguing that. I have pretty high confidence that if you have the vaccine you won't transmit the disease - I suspect the scientists are just being overly cautious because they don't have the data yet (though it is now starting to prove this out). They don't have the data in part, because the trials did not test asymptomatic people. This means it's possible that some of the vaccinated people in the trial caught the virus, but at a reduced severity that was asymptomatic (but still transmissible). Pretend that the vaccine reduced severity, but most people still caught it and were just asymptomatic. In that world, the vaccine wouldn't be enough (and the trials would not have revealed this). Since we know that some people who get the vaccine do catch the virus, but just have a mild case - it seems like a plausible outcome that others catch it without symptoms, but can still transmit it. That said, it's looking like that's not the world we're in - and the vaccines do just stop you from contracting the disease in addition to reducing severity in the rare case you catch it anyway. mRNA vaccines are new and given the asymptomatic transmission of the virus is why we have a pandemic, it's a reasonable thing to be cautious about (which is why I was surprised the trials only tested symptomatic patients).
sampo 6y ago
> So have there ever been vaccines that prevent you from getting getting the disease while still allowing you to spread it? In chicken, Marek’s disease works like that. https://en.wikipedia.org/wiki/Marek%27s_disease#Prevention https://en.wikipedia.org/wiki/Marek%27s_disease#Prevention
mLuby 6y ago
According to this, most vaccines are as you describe: "There are two main types of immunity you can achieve with vaccines. One is so-called 'effective' immunity, which can prevent a pathogen from causing serious disease, but can't stop it from entering the body or making more copies of itself. The other is 'sterilising immunity', which can thwart infections entirely, and even prevent asymptomatic cases. The latter is the aspiration of all vaccine research, but *surprisingly rarely achieved*." https://www.bbc.com/future/article/20210203-why-vaccinated-people-may-still-be-able-to-spread-covid-19 Side note—I wonder if these scientists were inspired by Spider-Man (1962): "Nearly 40 years ago it was observed that sterilizing immunity against [Malaria] could be achieved by exposing human volunteers to the bites of irradiated mosquitoes carrying sporozoites in their salivary glands." https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sterilizing-immunity
amluto 6y ago
Polio. The injectable vaccine prevents nervous system damage. The oral vaccine prevents transmission too. The problem is that the oral vaccine is old technology and can revert to being dangerous. It’s rare but happens. So countries with resources gave everyone the IPV to protect them and then the OPV to eradicate the disease. Tetanus is a partial example, too. The tetanus vaccine protects against the tetanus toxin but has no particular effect on whether you can have the bacteria replicate in your body. But tetanus isn’t transmissible, so this doesn’t matter much.

maxerickson 6y ago

It'd be a logistical nightmare to setup validated testing and so on for tens of thousands of participants. The studies coming out that did regular testing focused on easily reached populations (medical workers) that may not have been representative of the wider population (so not suitable for the trials). https://www.nejm.org/doi/full/10.1056/NEJMc2102153 https://www.nejm.org/doi/full/10.1056/NEJMc2102153 https://www.nejm.org/doi/full/10.1056/NEJMc2101927 https://www.nejm.org/doi/full/10.1056/NEJMc2101927

fossuser 6y ago
Couldn't they have at least done the rapid antigen test when they came in for their second dose? Maybe I'm underestimating complexity (typical for an outsider), but just seemed surprising to me when I heard that.
- sampo 6y ago
  Antigen test should show positive on vaccinated people.
dcolkitt 6y ago
Just collect data on the rate of infections of the members of the households of those in the study. Run an IV regression on the results. Since a significant fraction of transmission comes from those sharing a household, protection against asymptomatic transmission will show up in lower household infection rate among the vaccinated group.
- maxerickson 6y ago
  Preventing severe infection is a fine endpoint though. A vaccine or treatment that does that is a minimum viable tool for moving forward. Reduces deaths, reduces utilization of medical resources, etc, and then when it's a vaccine, it's pretty likely that it also reduces transmission. But it doesn't need to reduce transmission to be worth an awful lot.
  - 6y ago

caddemon 6y ago

AFAIK the impact of asymptomatic transmission is still under debate. The bigger danger seems to be presymptomatic transmission. But my info may be a few months out of date, would be interested if anyone has any sources saying otherwise? Still though I agree it would have been useful to regularly test all trial participants - the US really could have done a lot better job with testing more generally.