I am just curious what this looks like numerically to meet the 50% effective criteria in a population of 30,000 (do you skew this toward those in the high risk category?) how do you calculate 50% effective?
Good question. In the Phase 3 trials, half will get placebo, so only 15000 will get the vaccine being tested. They will be observed to see how many get the disease in the community. If, say, 1500 get Covid in the test period in the placebo group, and 750 get Covid in the vaccinated group, that would be 50% efficacy, as I understand it is defined.
Of course, that is not the full picture. Immunity is not an all or none thing, and if you look at such things as hospitalization rates, and deaths, you may find partial protection from severe disease. With flu, in pediatric populations for example, most years about half the kids get immunized, and those that still get flu who are immunized, have about half the risk of dying when they get get it compared to unimmunized kid, as I recall.
In addition, study participants will get tested for antibody production in response to the vaccine as well as from community disease. The production of antibodies to the vaccine is not enough, as they must be protective. Then longer term, you get into cellular immunity which gets complicated, and at times takes years or decades to follow for efficacy.
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Thanks Phil. This is helpful. Its just seems that since we have an unknown variable on the infection related to over 50% being asymptiomatic and exposure rate that would cause a dampening of the benefit signal, wouldnāt it be better to focus the study on those that are most at risk for exposure such as healthcare providers and the higher risk individuals such as those of higher age, high bmi, darker skin, metabolic disorders and hypertension? After all we test the shingles vaccine on those at risk for shingles not 20 year olds?
The point made by Baric was that we need to develop treatments for the high risk populations. It seems to me that If you can show protection of the high risk then you can prove efficacy of the vaccine.
Because only people who have had chicken pox are at risk from shingles. That would be people born before a chicken pox vax was available. Chicken pox and shingles are caused by the same virus, varicella zoster, which hangs around in the body. And your immunity declines with age. (Bummer!)
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Better to develop a vax thatās safe and effective, and then prioritize the deployment of the vax: healthcare providers, the elderly, etc. receiving it first.
My own clinical trial is looking for healthy subjects ages 18-85.
We applied for the Moderna one being done in a town nearby, but we havenāt heard back. We did get emails saying they would still get back to us. Iām not sure we would be good candidates, though, since we stay pretty isolated and try not to have much exposure.
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I would pursue it even if you are relatively sheltered. Things can change really quickly with this virus! What state are you in? Iām in Connecticut.
We are in Nebraska. Weāve registered, but as I said, we havenāt heard back. I think theyāll call us.
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My place didnāt call me so I called them. They assured me that I havenāt been forgotten. I should hear something this week.
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There is a debate on how to roll out this vaccines if proven safe and effective. There are two main strategies for the roll out basically hit hotspots and try to stem the spread in those spots. This basically would require a high vaccination rate and given that maybe only 50% effectiveness that may not be very effective in significantly reducing the transmission rate and may result in greater loss of lives. The other alternative is focus on the most at risk professions and the most at risk populations as mentioned older age, high BMI metabolic syndromes hypertension, darker skin. This is why it makes best sense to focus testing the vaccines in these populations as these are the demographic that are most dying and effected by this virus. By testing the virus just in the general population will neither confirm effectiveness or safety particularly due to the low number that will be exposed and infected and also the high percent that are asymptiomatic.
That is the medical opinion but IMO it is wrong. Old people are more stressed than younger people, which means their immunity will be declined. It is not that their immunity is declined due to age.
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Vaccination is talked about as immunization but this is not the reality. Vaccination gives a person the advantage of developing antibodies so that their immune system is ready to fight an infection, and given that they are not stressed, which would mean their immune system would be to some extent declined. Vaccination does not stop infection as in the virus or pathogen entering the body.
A vaccinated person is most likely to be asymptomatic because their immune system is effectively fighting the infection. However that doesnāt mean that for a short time they are infectious, that is that they may transmit the pathogen to others.
I got an email saying they were still waiting for approval. I almost marked the email as spam before reading it because it said it was from ānarc-1 copyā. NARC is an amusing name for a drug research company. 
I think itās North Alabama Research Center.
They are accepting any adult that volunteers. So if you know someone who is high risk and is in an area where itās being tested, encourage them to sign up! They want a diverse testing pool.
The 50% effectiveness number is the minimum goal, not necessarily what they expect from the vaccines currently being tested. It very well could be much more effective than that.
Iām not sure what youāre talking about with asymptomatic folks in regard to testing the vaccine. I think the trial participants get tested for Covid during the trial, so i think theyād catch the asymptomatic people.
For rollout, Iāve only heard from high up officials the idea of doing high risk people first, including health care workers. Of course, many of these vaccine companies are mass producing their vaccines during the phase 3 trials, at much financial risk, so they can distribute ASAP after approval, assuming the phase 3 trials went well. The United States will probably have plenty. The third world countries, not so much. 
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I think all that is taken into consideration. Your comment on greater loss of life doesnāt seem to be an issue, as asymptomatic people do not seem as infectious, though much is still unknown. Only if a vaccine causes false security and more reckless behavior in the unvaccinated would there seem to a problem. Iām more worried that the reckless people who now refuse to wear a mask will also be the ones refusing vaccination, preventing a return to normalcy for the rest of us.
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Some of the people saying we should use hydroxychloriquine without RCTs showing its effectiveness are the same people that will complain about vaccines being ārushedā. They already complain about existing vaccines (ie, the anti-vax movement).
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Well, Iāll just go with the medical opinion.
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Iām old, and Iām less stressed than when I was younger! Thatās true for a number of older people I know, too, so Iām not sure where that idea comes from.
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Same here! "
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I should have said a lot of older people are stressed. Sure there are plenty that are not stressed. A lot depends on who is in their lives.
Itās also ok to acknowledge what we do know. The natural infection induces the production of some of the same antibodies the vaccine will induce. Therefore, we can learn a lot from how recovered patients have reacted to new viral exposures and if there are problems with enhanced reaction to new infections or issues with protein mimicry that could result in autoimmune diseases. Previously infected people also hold data on how long protective antibody titers remain in the blood and tissues.
One potential issue is the question of why some people have a prolonged recovery or lack of recovery from these infections. I suspect that it is due the innate immune response and not the adaptive immune response (i.e. antibodies), but it is still entirely possible that specific antibodies in specific patients are causing problems. The efficacy of steroids in reducing mortality and morbidity certainly points to an immune response playing a role in severity.
A vaccine would prevent an infection from taking place so there would be a drastic reduction in asymptomatic infections among the vaccinated group, or at least there should be. Antibodies are able to tag viral particles and have them cleared from the body before they can set up a significant infection.
I think there is plenty of evidence demonstrating that antibodies resulting from SARS-COV2 offer protection from subsequent infections. This is supported by the fact that infections go away over time. This isnāt the case with HIV.
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