Hello The most commonly followed schedule for pneumococcal vaccine is 3+1 (at 6,10,14 week and then at 12-15 month of age)schedule. Pneumococcal vaccine (conjugated like PCV13) can be given from the age of 6 weeks upto 5 years as pneumonia is more severe in this particular age group and which can be prevented by vaccination. There are various studies according to which protective efficacy against pneumococcal pneumonia varies between 80-98% after complete vaccination. Now the schedule changes according to age category. As your child is in age group of 12-23 months only two dosage are needed which should be at least 8 weeks apart. So next dose of PCV 13( pneumococcal conjugate vaccine) in your child will be needed 8 weeks after first dose that is at 18+ months. Wish you and your family good health Regards