People who received vaccination against the H1N1 swine flu bug might also get protection against the strain of influenza that killed around 50 million to 100 million citizens in 1918, researchers reported on Tuesday.

Tests on mice could show that the vaccine for the still-circulating strain of H1N1 helped in protecting against the older bug, which is a distant cousin and also called H1N1, the squad at Mount Sinai School of Medicine in New York said.

No one is worried that the 1918 flu will make a comeback in the due course of time but there are apprehensions that someone may try to bring back to life or reconstruct it for a biological attack.

The study that has been published in Nature Communications also depicts that the vaccine has cross-protection against associated flu strains.

The old virus was rebuilt by scientists by making use of samples dug up from the frozen bodies of the individuals in Alaska that died due to the virus and using genetic sequences from sealed samples.

The study while carrying out experiment found that the mice vaccinated against H1N1 swine flu, lived. Almost 80% of mice that had been vaccinated with a seasonal flu vaccine that was designed to guard against a 2007 strain of H1N1 lived, even when infected with the 1918 flu.