Decreasing your calorie intake by about 500 calories per day will stimulate safe weight loss of about 1.1 pounds (0.5 kg) per week. This amount of weight loss is considered safe for breastfeeding women. You may search in Google the TDEE calculator to computer your total calories per day.
Also...
Safer to get vaccine after pregnancy. When I got vaccinated I asked for a friend whether it's okay for breastfeeding moms to get the vax and she said yes.