Following a 2 1/2-hour meeting Thursday night between Secretary of State Cyrus R. Vance and Soviet Ambassador Anatoliy F. Dobrynin, the State Department reported yesterday that an additional meeting or meetings of the two are expected before completion of a new strategic arms limitation treaty (SALT).

Spokesman Hodding Carter would give no details of the Vance-Dobrynin session except to say that "SALT" was at the heart of it" although other matters were also discussed. There were indications that the unusual length of the meeting, which began at 6:30 p.m. was partly a result of socializing.

"For the moment, we have neither a summit meeting or a treaty in hand," said Carter. In response to questions, he said there is "no indication" that the current illness of Soviet leader Leonid Brezhnev will affect SALT. Brezhnev is officially reported to be suffering from a case of flu.

Informed U.S. sources said Vance presented Dobrynin with the latest American statement on the encoding of missile test data, or telemetry. The United States is sseeking to fashion a clear understanding through diplomatic exchanges of the limits of such encoding under SALT II.

Vance is also reported to have presented the latest U.S. compromise plan on the definition of new missile systems permitted in the treaty Final details of the telemetry and new missile questions are said to be the only major issues outstanding in the SALT negotiations.