A vaccine that protects people against coronavirus is nearly 95% effective.
That's according to early data from US pharmaceutical company, Moderna, which tested its vaccine on 30,000 Americans.
It's the second company to announce successful trial results, and comes a week after another trial of a vaccine offered 90% protection from the virus.
However, the vaccines have not been approved for use yet and it's not known how well they work on the elderly or how long the immunity lasts for.
Another big vaccine trial to help protect people from coronavirus has also started in the UK.
The jab - which is designed by the Belgian company Janssen - uses a genetically modified common cold virus to train a person's immune system.
The Janssen trial has started the job of recruiting 6,000 people in the UK to take part. Other countries will join the effort to bring the total up to 30,000.
Half of the volunteers will be given two doses of the vaccine around two months apart.
It could take six to nine months before the results are available.
The UK government has already put in advanced orders for six coronavirus vaccines, including 30 million doses of the Janssen jab.
If these vaccines are approved to be used on the public the government has said it will be given to older people who are at most risk first.
Children are not likely to get vaccinated but they will benefit from others having the jab because of something called herd immunity.
Different countries and scientists have been trying to come up with a vaccine for Covid-19 which means there are lots of trials going on at the moment.
Scientists believe that many types of vaccines will be needed to end the pandemic.
So far, they know that the vaccines which have been successfully tested are effective in the short term.
It's believed that one company won't have the capacity to offer the number of vaccines needed to treat everyone on the planet.
It's also thought that some vaccines will work better for certain age groups.