Really, it just means a) it works, b) the study should go on longer to get more significant results.

That relative risk reduction is very signficant, not just statistically signficant, it is very practically signficant too.

Sure, but the sample of confirmed positives is so small that it might not include some important subgroups. If only 1 at risk person in the placebo tested positive, and 0 in the vaccinated group did we haven't learned much.

How much longer? There is significant benefit to rolling out massive amounts of vaccine immediately. I know that any scientist worth their salt will almost always claim that more study is warranted. But we're playing against a clock measured in human lives right now

And if this vaccine doesn't work or has nasty side effects, or even ends up killing people, most people will be very reluctant to take it, or any of the next better vaccines, and that would cause even more deaths.

It's a hard problem, and even though the clock is ticking, we also need to get it right the first time.

The relevant piece for most people to know is that based on data from a short time period, people were 20x less likely to get symptomatic COVID if they get the vaccine. The exact number will probably change a bit as more time goes by and more data comes in, but 20x is the ballpark.

Things we still don't know:

- Does the vaccine also stop you from contracting the virus asymptomatically and spreading it? People enrolled in the trial were only told to get tested if they showed symptoms.

- How long does the immunity from the vaccine last? We won't know this for some time.

A new study of 185 COVID patients found that 90% of the subjects were still seropositive for neutralizing antibodies at the 6 to 8 month time points. B-cells specific to the Spike and to the nucleocapsid coronavirus proteins actually increased over a five-month period. Memory T cells appeared to have half-lives of at least five or six months in these patients, and helper T cells were completely stable over the entire period studied.

https://www.biorxiv.org/content/10.1101/2020.11.15.383323v1

I presume how long immunity lasts is based on how well and quickly the virus can mutate itself? Do we have any research on other Coronaviruses that might hint at how long immunity will last?

That's part of it, but it also depends on the 'memory' of your immune system.