People who became infected with Covid-19 after getting a messenger RNA vaccine carried less virus and had shorter cases than unvaccinated people who became infected, a study by government health researchers found. Sixteen people in the study who got infected, despite taking a Pfizer Inc. or Moderna Inc. vaccine, had on average 40% less virus in their nose … The vaccinated individuals also had a 66% lower risk of having detectable virus for more than one week, and they had a shorter duration of illness, with about two fewer days spent in bed, the study said.