[M T]

Suppose a large number of people chose to voluntarily forego or delay their 2nd shot, putting themselves as a cohort of people only getting the single dose.   Say, they wait 3 months or 6 months for their 2nd dose.

They would provide 3 benefits, at a risk to themselves,
1)  More people would get at least the first dose more quickly simply by their delay
2)  They could provide evidence for whether a single dose is effective.
3)  #2 could conceivable allow first doses to be declared sufficient, in time to finish vaccinations earlier.

Among the people that might decide this are health care workers who got their first dose first.  By being among the first, evidence from their experience would be available most quickly.

What does the current science suggest for the effectiveness of just one dose?  I’m assuming it reduces risk by some factor.  Is that correct?

Something around 1100 people in each of the vaccine & placebo arms of the Moderna trial did not get a 2nd dose.  Many were removed for cause.  But of what was left, Moderna had a handful of cases.  Their very weak numbers had a 54% effectiveness but a 95% confidence interval from -300% to 95%.

Even so, that's better numbers than those doing Moderna's trial knew when they started.

[M T]

Suppose a large number of people chose to voluntarily forego or delay their 2nd shot, putting themselves as a cohort of people only getting the single dose.   Say, they wait 3 months or 6 months for their 2nd dose.

They would provide 3 benefits, at a risk to themselves,
1)  More people would get at least the first dose more quickly simply by their delay
2)  They could provide evidence for whether a single dose is effective.
3)  #2 could conceivable allow first doses to be declared sufficient, in time to finish vaccinations earlier.

Among the people that might decide this are health care workers who got their first dose first.  By being among the first, evidence from their experience would be available most quickly.

What does the current science suggest for the effectiveness of just one dose?  I’m assuming it reduces risk by some factor.  Is that correct?

Something around 1100 people in each of the vaccine & placebo arms of the Moderna trial did not get a 2nd dose.  Many were removed for cause.  But of what was left, Moderna had a handful of cases.  Their very weak numbers had a 54% effectiveness but a 95% confidence interval from -300% to 95%.

Even so, that's better numbers than those doing Moderna's trial knew when they started.