Transmission
This report says that seroprevalence of COVID-19 antibodies from infection in Canadian blood donors went up to 4.5%, up from 4.0% in May. (How can they tell the difference? Vaccines only make antibodies to the spike protein, so if there are antibodies to some other part of the SARS-CoV-2 virus, then it was acquired by infection.) Racialized groups had more than double the seroprevalence (8.0%) of whites (3.7%).
They also found that seroprevalence was highest in 17-29 year-olds (9.3%), especially in the Prairies (17.5% in Alberta!!).
Vaccines
This study, if I understand it correctly, says that MMR and Tdap immunizations give some protection against severe COVID-19. I’m also seeing some chatter around that article speculating that maybe the reason kids don’t get COVID-19 as much as adults do could be because their MMR and Tdap vaccinations are more recent. (Note that this is wild speculation.)
Meanwhile, this study (from July 2020) suggests that the reason smokers have some resistance to COVID-19 might be because they were infected with Tobacco Mosaic Virus (TMV), and that revs up their immune system. TMV doesn’t make humans sick, but the human immune system does notice it and stimulate both the innate and adaptive immune systems.
Recommended Reading
This opinion piece says we should all get a flu shot.