The research shows those vaccines may be able to protect against the infection for years.
The study published in the journal "Nature" shows the Pfizer and Moderna vaccine produce strong antibodies against the virus.
Researchers also looked at other parts of the immune system including the B-cells. They may help train the body to prevent the infection long-term.
Dr. Judith ODonnell, an infectious disease specialist at Penn Medicine, said there is still a lot to learn, but this is promising research.
"This study is really telling us that the immunity after COVID-19 vaccination is going to be much longer lasting than we had anticipated and could be well beyond the 6 to 12 months where many people were thinking a booster might be needed," she said.
The study only looked at the mRNA vaccines. It did not look at the Johnson & Johnson single-shot vaccine.
One potential wild card is variants of the virus. We know the vaccine works against the Delta variant, but if the virus were to change significantly then the components of the vaccine might need to be adjusted and that would mean a booster shot.
The best way to prevent more variants is by getting more people vaccinated here and abroad.