American confidence in the major social institutions has risen dramatically in the past year with the impact of Watergate and the Vietnam war receding from public consciousness, according to two extensively public opinion surveys.

For the first time in four years, the public's respect for those institutions rose significantly in 1977, according to a Louis Harris survey issued yesterday.

Of the 16 institutions tested, 15 have risen in public confidence in the last year, the Harris poll showed. The largest increases were recorded by doctors, college presidents and leaders of organized religion.

At the same time, an extensive survey of young people by the University of Michigan's Institute for Social Research showed a sharp drop in the level of cynicism and suspicion toward such embattled institutions as the presidency, the Congress and the police.

The Michigan group found, concurrently, that increasing numbers of youth feel that such institutions as the Supreme Court and the medical profession are doing either a "good" or "very good" job for the public.

"It doesn't surprise me much at all. With a change of administrations since Watergate, there is bound to be a general shift in attitudes," said Lloyd Johnston, associate research scientist at Michigan's social research unit.

Emphasizing that he lacked specific data to support a conjectural explanation of the phenomenon, Johnston added in a telephone interview, "I believe this produces a kind of halo effect - it spills over to the other institutions unrelated to the government."

Both national surveys were conducted during the close of 1977 and involved sizable samples, 1,498 adults in the case of the University of Michigan study.

The Harris study showed that for the first time since 1973, a majority of Americans - 55 per cent - now places a "great deal" of confidence in people running the medical profession.

At the other end of the scale, the news media was the only institution to record a drop in confidence from a year ago, the Harris poll showed. However, the 1 percentage point decline may not be statistically significant because of the 2 point plus or minus sampling error allowed for that large a survey, statisticians said. [TEXT OMITTED FROM SOURCES]