  A search is presented for pair production of heavy vector-like T and B quarks
in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The data sample corresponds
to an integrated luminosity of 35.9 fb$^{-1}$, collected with the CMS detector
at the CERN LHC in 2016. Pair production of T quarks would result in a wide
range of final states, since vector-like T quarks of charge 2$e$/3 are
predicted to decay to bW, tZ, and tH. Likewise, vector-like B quarks are
predicted to decay to tW, bZ, and bH. Three channels are considered,
corresponding to final states with a single lepton, two leptons with the same
sign of the electric charge, or at least three leptons. The results exclude T
quarks with masses below 1140-1300 GeV and B quarks with masses below 910-1240
GeV for various branching fraction combinations, extending the reach of
previous CMS searches by 200-600 GeV.
