The nation's top experts on influenza, mindful of last year's swine flu debacle, agreed yesterday to recommend to the U.S. surgeon general only that work continue on the development of a vaccine to combat the new Russian flu, which now has caused major outbreaks in five countries.

The group was unable to agree on little else, other than targeting those above 65, and those suffering from chronic diseases, as the group to receive a vaccine if and when it is produced.

Last year, many of the same experts strongly recommended a national immunization program against a disease that never spread beyond the gates of Ft. Dix, N.J. Some serious physical reactions to the shots occured, plunging the program into considerable controversy. This year, the group is being cautious to the point of inaction.

One problem facing the group, particularly in the light of last year's experience, is a lack of knowledge concerning the seriousness of the flu threat.

While all attending the meeting at the National Institutes of health, in Bethesda, agreed to agree that the flu will reach this country, probably this spring or next fall, they do not yet know how direct a health threat it poses.

Three American officials will be traveling to Russia next week to confer directly with Soviet health officials, and American epidemiologists hope to have a better idea what the extent of the problem is after that trip.

In the meantime, the surgeon general is expected to produce a set of recommendations by early next week that then will be given to a policy committee to implement.

Among matters known about the flu from work done thus far with the A/USSR/76 virus are:

Those persons over 63 and under 23, the most susceptible groups to flu, have virtually no antibodies against the virus.

Those is the 24 to 34 age group, the healthiest group least affected by influenza, have the best natural protection because of exposure to a somewhat similar virus in the 1947 to 1950 period. The elderly have lost what antibodies they developed at that time.

It is probably no more virulent, will make persons no sicker, than any other strain of flu.

It is quite easily reproduced in eggs, making the production of a vaccine a relatively easy matter.

The virus is likely to affect a large proportion of the population because school children, who play a major role in spreading infections, have no natural protection against it.

M.R. Hilleman, of Merck Sharp & Dohme, pharmaceutical manufacturers, told the meeting that he believes the new strain of flu is a mutation of a strain that escaped from a laboratory somewhere.

Because the virus is similar to the HINI strain seen in 1947, and is, in fact, a form of the HINI, Hilleman said it "must have persisted some place.

"One possibility is in man - though no such human reservoir maintenance is known . . . The alternative reservoir is a deep free somewhere, somehow, that contained stored . . . virus of the (1947) variety that was released by man, by error, intent, or laboratory worker infection. This seems a possibility, with no intent to state that it actually happened," said Hilleman.

The policy committee, which will report to Health, Education and Welfare Secretary Joseph Califano, will have to decide what vaccine should be produced, how much of it should be produced, who should get it, and whether it should be given as part of a federal program.