A new experimental smallpox vaccine is much safer than the old one, say researchers.

This vaccine is known as modified vaccinia Ankara (MVA). Tests on monkeys and mice have shown it to be effective against a pox virus, say the researchers.

You can read about this in the journal Nature (about the trial on monkeys).

The trial that was carried out on mice is published in the journal Proceedings of the National Academy of Sciences.

The research was done at the National Institute of Allergy and Infectious Diseases.

In traditional smallpox vaccines there are side effects such as sores on the skin (and other things). Scientists noticed that the monkeys did not develop these side-effects when they were administered this new vaccine.

The mice became immune to a lethal dose of vaccinia virus - this is a similar virus to smallpox (same family).