Does the moderna vaccine 100% protect against severe covid-19 after the first dose?

NO it does not! Initial injection requires a 2 week period before 2nd dose, then 2 weeks for max benefit of 94+%. There would be some benefit 2 weeks after initial dose, but I have not seen that listed. Protecting against variants has been inconsistent and there is no firm data on how successful Modena would be. Remember J&J did test in UK and Africa and was 66% effective there 28 days post inj

“The Moderna vaccine can provide 80.2% protection after one dose, compared to 95.6% after the second (in people aged 18 to 65 – it's 86.4% in those over 65)” REF: https://www.bbc.com/future/article/20210114-covid-19-how-effective-is-a-single-vaccine-dose *& Please be aware that this would be at least 14 days after vaccination.