Not sure I can since the 2018 numbers (this year's match) aren't public yet. Those of us who applied this cycle can see them through the NRMP site.
The data is now public on the NRMP website. NRMP --> Data and Reports --> Fellowship -->
NRMP Results and Data Specialties Matching Service, 2018 Appointment Year
Total applicant numbers were down from 174 to 141 (2017 --> 2018), which is a 5-year low. The bar graphs show there were 17 positions across 15 programs that went unfilled, though when I search the programs I can only account for 16 positions in 14 programs. Many of these programs are currently 3 year fellowships, with 2 years of a T32 research fellowship built in.
Unfilled programs
Stanford (medicine, 0 of 1)
Stanford (peds, 1 of 2)
UC Irvine (med or peds, 0 of 1)
UCSF (medicine, 0 of 1)
Yale (med or peds, 1 of 2)
Northwestern (peds, 0 of 1)
Indiana (med or peds, 0 of 1)
Hopkins (peds, 0 of 1)
Boston Children's (0 of 1)
UNC (med or peds, 0 of 2)
Cincinnati (peds, 1 of 2)
CHOP (peds, 1 of 2)
U Tennessee (med or peds, 1 of 2)
UTMB (medicine, 0 of 2)