Is that also true of the Pfizer and Moderna trials? Are the various trials measuring 'effectiveness' in the same way? Is there a standard for 'effectiveness' in these Covid-19 trials?
It will take some digging and real effort to compare the risks and benefits of the various vaccines coming to market.
Just as a reminder, that vaccine had more than 40k people in each group, with 170 cases of COVID-19 being observed, 162 in the placebo group, 8 in the vaccine group.
As you can see, the sample sizes get quite small, so I’m not sure how much, if anything, this tells you regarding severe cases. There could have been just as well no severe case in the treatment group, just by luck. What would that tell us?
I didn’t find any info regarding severe cases and the Moderna vaccine but I maybe I missed it. Those press releases are hard to read.
My source is Pfizer’s press release: https://www.pfizer.com/news/press-release/press-release-deta...
https://clinicaltrials.gov/ct2/show/NCT04368728
Everybody in all arms (groups) gets a jab, twice, but what exactly what is in the needle varies. The study paperwork doesn't say which placebo was used in this trial (the participants would definitely have been told), sometimes vaccine studies use a vaccine for something else that you didn't need but is presumably harmless (e.g. think of vaccines you take when going somewhere a bit dubious on holiday). Other times they just use saline. Some other groups got higher doses of vaccine.
Anyway, since everybody got stabbed, nobody (as much as possible not even the people giving you a jab) know what's in the needle - everybody gets assessed for side effects. One of the very revealing things about all these studies is how many side effects you get for injecting people with saline. Sore arm makes some sense at least, somebody stuck a tiny needle in your arm - but you'll get headaches, dizziness, flu symptoms even. The mind is powerful.
Maybe its chance that none of those 39 got really sick. I'm not sure what the age breakdown of trial participants was- were the people in the oxford trial younger? Did the distribution match the distribution from the mRNA trials? I have no idea.
But you're less correct about saying "smple size is probably too small" (in general, people really really really need to stop dismissing things based on sample sizes until they actually go through a Power calculation!). Your question about demographic breakdown is entirely valid.
Hospitalization rate for covid is about 228.7 hospitalizations per 100,000 population [0]. Or, more easily interpretted, about 10-20% of cases turning to hospitalization. Taking the more conservative (10%) rate, we'd need 31 samples for a 95% CI and 5% margin of error. Thus, the interpetation is that is it unlikely that the _lack of seeing any hospitalizations in the vaccine+covid-positive group is by chance_.
Hope that helps!
[0] https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covidvi...
I think there was a bit of an implication in the parent post that it would eliminate hospitalizations (instead of just reduce), i still think that is unrealistic.
Yes, its true that there were no "severe" cases in the other vaccine trials as well.
> This statement seems a big deal: "There were no hospitalised or severe cases in anyone who received the vaccine"
It may be. When considering disease severity, we are no longer looking at a pool of people who have been given the vaccine (which is in the tens of thousands for all of these), we are looking at a pool of people who got sick. That means the sample size is reduced to approximately 90-100 for placebo wing of each vaccine, and 30 for ChadOx vaccine arm, and about 5 for Moderna/Pfizer vaccine arms each. That's fairly small.
Seems like the estimated rate of severe cases is around 10-20%. Assuming its 10% (which would mean its harder to identify an actual reduction in disease severity rate from the placebo group), then in the case of Pfizer/Moderna, there would be a greater than 50% chance of seeing no severe cases in a group of 5 infected, vaccinated patients, even if there was no effect on the severity of the disease. The greatest benefit to the vaccine is that they seem to prevent infections substantially, but that also means it will take months before enough infections occur to get some kind of statistical significance on if severity is also affected.
But with this vaccine, 30 cases with no infections is definitely in the realm of statistical significance. I don't have the exact numbers from the trial, but if it indeed is 0/30 vs around 10/100 between the vaccine/placebo wings, it definitely meets the typical thresholds of statistical significance.
It's important to note that, at least according to my understanding, the Pfizer/Moderna trials are measuring symptomatic cases, not doing actual tests on their trial participants. This means that it could well mean that the reason the vaccines appear to be so effective is because they truly are reducing the severity of the disease to the point of being asymptomatic. We just aren't able to see it yet due to the way the data is being collected.
The Pfizer press release states: "There were 10 severe cases of COVID-19 observed in the trial, with nine of the cases occurring in the placebo group and one in the BNT162b2 vaccinated group."
So, zero severe cases for Oxford, and one for Pfizer. Interesting.
Should also point out the Pfizer trial may have had 43,000 participants, and the Oxford one 24,000, so they are different size trials. Also, it's super easy to miss important details when comparing outcomes like this, to do this properly really requires a project or in-depth investigation, not my 15-minutes research effort. :)
Pfizer release: https://www.pfizer.com/news/press-release/press-release-deta...
Seriously, do you think this is a huge difference in quality of measurements?
And it's pretty easy to compare the vaccines. It will mostly come down to price, ease of manufacture and ease of distribution i.e. temperature. Given that for the 3 viruses all have no risks associated with their use.
“There were 10 severe cases of COVID-19 observed in the trial, with nine of the cases occurring in the placebo group and one in the BNT162b2 vaccinated group.” (1) “170 confirmed cases of COVID-19 were evaluated, with 162 observed in the placebo group versus 8 in the vaccine group.”
1) https://www.pfizer.com/news/press-release/press-release-deta...
I think the commenter wanted to know whether anyone who received the vaccine was hospitalized for anything covid related, not for anything vaccine related.
a) A virus that is known to cause severe disease in a significant proportion of people, including months-long serious health effects, hospitalisation and death.
b) A virus chosen because it doesn't causing any ill-effects in humans, modified to take on some non-harmful aspects of virus a) and found to not cause any significant harm in tens of thousands of people over several months.
Which is more likely to cause long-term side effects?