Clinical trials of around 4,000 individuals have shown that half the current dose of its U.S.-approved vaccine Fluvirin gives immunity to adults, the Swiss drug maker said in a statement.
The company's H1N1 flu (also known as swine flu) vaccine for the U.S. contains no adjuvant, a chemical compound that hasn't been approved by the U.S. Food and Drug Administration but which often is used in vaccines sold in other countries to boost the immune system and stretch the vaccine's active ingredient.
Novartis is discussing the findings with the Food and Drug Administration, which is assessing whether the amount of vaccine per dose can be reduced in the United States.
In Europe, Novartis has been using an adjuvant for flu vaccines since 1997. A separate study of more than 33,000 participants showed that the adjuvant is well tolerated, the company said. A single shot containing the adjuvant and half the amount of vaccine used in Fluvirin is enough to protect children between 3 and 8 and adults, according to the study.
Novartis said using the adjuvant in the U.S. could allow the immunization of four times more people with current vaccine supplies.
Shares in Novartis were down 0.6 percent at 54.20 Swiss francs ($53.57).