Not about SARS-CoV-2 but these two studies convinced me to wear some type of mask.
The first is about household transmission of influenza-like illness from a sick child to an adult with or without a mask. There are caveats but in the household, at least:
“We estimated that, irrespective of the assumed value for the incubation period (1 or 2 days), the relative reduction in the daily risk of acquiring a respiratory infection associated with adherent mask use (P2 or surgical) was in the range of 60%–80%.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662657/pdf/08-1167_finalRCME.pdf
The other found no significant difference in the incidence of influenza between health care workers wearing N95 or Medical(surgical) masks.
https://jamanetwork.com/journals/jama/articlepdf/2749214/jama_radonovich_2019_oi_190087.pdf
I’ve decided to use a DIY mask made from a double layer of cotton t-shirt with some sort of filtration material in between. I’ve worn mine a few times, and it’s been comfortable enough. I’m undecided on the filter. I’ve only used a double layer of paper towel so far. Blue shop towels are supposedly better, and I have a MERV 12 air filter sitting around that i may decide to tear apart.
I may end up getting COVID-19 eventually anyway, but i’m hoping some sort of mask may reduce the viral load.
May I suggest buying a high end (anti-allergen electrostatic 'premium') furnace filter and scavenging the filter media out of it? The static cling of the media will stop particles much smaller than the pore size.