The Food and Drug Administration yesterday announced approval of the first vaccine to combat the most serious form of hepatitis, a debilitating liver disease that poses a worldwide public health hazard.

FDA Commissioner Arthur Hull Hayes Jr. called the new vaccine for hepatitis B a "major advance" that has the potential "to eliminate or greatly reduce the spread of this major, costly disease." Tests on humans show that it can be as high as 96 percent effective.

He noted that it was the "first completely new viral vaccine in 10 years and the first vaccine ever licensed in the United States that is made directly from human blood."

Government and drug company officials yesterday cautioned that it was not being recommended for use by the population at large. They predicted, however, that initially targeting the vaccine to individuals at "high risk" could cut the hepatitis B incidence in half. Hepatitis B, formerly known as serum or post-transfusion hepatitis, is one form of the disease and is spread through contact with blood and secretions such as saliva and semen from infected individuals. It is capable of doing permanent liver damage and is potentially fatal.

Hepatitis A, caused by a different virus that is spread through contaminated food and water, is considered more common, but its long-term consequences are generally more mild. It is declining as sanitation improves throughout the world.

Federal estimates suggest that there are more than 200,000 new hepatitis B infections each year in this country, with 50,000 of them serious enough to cause acute illness and signs of jaundice, and perhaps 200 resulting in death.

But even the mild cases can lead to chronic disease and liver damage in thousands more. And at least 400,000 Americans are chronic carriers of the virus who can go on to infect others.

Because recent research has implicated chronic hepatitis B infection in the development of liver cancer, Hayes noted that the new vaccine "may save people not only from an infectious disease, but from one form of cancer as well."

Donald Francis of the Centers for Disease Control said that roughly 10 million Americans would fall in the "high risk" category for contracting hepatitis B.

They include health care workers--those who handle equipment in blood banks or kidney dialysis units, surgeons and dentists--as well as drug addicts and sexually promiscuous individuals, particularly male homosexuals.

The vaccine, which is produced through a laborious process requiring 65 weeks, is not expected to be available until mid-1982. Officials at Merck Sharp and Dohme, the drug company manufacturing the vaccine, said that the price for a three-dose regimen has not yet been determined, but it is likely to be costly--from $75 to $120. Cheaper production methods such as the use of recombinant DNA, or genetic engineering, could eventually bring the cost down, however.

Francis said that candidates for the hepatitis B vaccine should probably be screened, since chronic carriers or those who already have protective immunity to the disease would not benefit. He said the disease was costing the U.S. economy at least $6.5 million a week in hospitalization and work loss.

Hayes said there was "no question" about the safety of the vaccine, which is produced with virus fragments taken from the blood of carriers of the disease (unlike other vaccines that are grown from cells in the laboratory). He emphasized that the final product was "highly purified" and treated to destroy any live virus.

Merck said that short-term side effects can include those similiar to other vaccinations, including mild discomfort at the site of the shot, rash, mild nausea and a temporary fever.

The development of the vaccine involved the collaborative effects of researchers from government, industry and academia, starting with the 1965 discovery by Dr. Baruch S. Blumberg of the presence of the hepatitis B virus in the blood of an Australian aborigine.