The pandemic has opened a new era for vaccines developed with gene-based technologies, techniques that have long stumped scientists and pharmaceutical companies, suggesting the possibility of future protection against a range of infectious disease.

Johnson & Johnson’s Covid-19 vaccine, which was authorized Saturday for use in the U.S., is at the vanguard of a class of shots designed to mobilize a person’s immune defenses against the disease. It will be the first Covid-19 vaccine administered in the U.S. that uses viral-vector technology, which employs an engineered cold virus to ferry coronavirus-fighting genetic code to the body’s cells.

J&J’s vaccine is the third to be authorized in the U.S. after ones from Pfizer Inc. PFE -0.98% and its partner, BioNTech SE, BNTX -2.94% and Moderna Inc. MRNA 4.33% In a late-stage trial, J&J’s single-shot vaccine was 66% effective in preventing moderate to severe cases of the disease that has killed more than 500,000 people in the U.S. and about 2.5 million world-wide.

“This is one of those giant leap moments for us. These are fundamental shifts in how we will build vaccines for the future,” said C. Buddy Creech, director of Vanderbilt University’s vaccine research program. “I think this really ushers in a golden age of vaccinology.”

New vaccine technologies spurred by the pandemic are leading efforts to combat Covid-19 and herald a new arsenal of weapons for fighting lethal viruses in the future, infectious-disease researchers said, another example of how the fight against Covid has supercharged technological development.

Viral-vector Covid-19 vaccines developed in China and Russia also have been authorized for use in those and other countries. The Covid-19 vaccine developed by the University of Oxford and AstraZeneca PLC, which has been authorized in the U.K. and other countries, also is a viral-vector shot.

For years, vaccines for such infectious diseases as measles and polio were made from the viruses they targeted, in versions scientists rendered harmless. The shots rally the immune system by exposing people to the targeted virus. Yet such vaccines could take a decade or longer to develop, and manufacturing them took months.

The mRNA vaccines and J&J’s viral-vector shot—developed and tested in months—were propelled by new insights into the immune system that opened the door to engineering a better defense.