Neither of these things are guaranteed to happen if you get the flu vaccine when you are sick, but they are possibilities. If you have just a mild illness, there is no reason to wait to get vaccinated.
Early in the day, let roast stand at room temperature at least 1 hour before cooking. Preheat oven to 375 degrees. Rub meat ... the outside and rare in the middle. Meat will be very brown ... stand at room temperature for at least one hour.
Preheat your oven to 500 degrees. Place the roast in a roasting pan or dutch oven and put it in the oven, fatty side up. Roast at 500 degrees, uncovered, for 7 minutes per pound. Our roast was a little over three pounds, so I cooked it for 25 minutes.