The nasal spray vaccine licensed in 2003 does contain live strains of virus that have been greatly weakened so as to safely provoke an immune response without causing disease.

(A live-virus vaccine is made using the live strains of a virus.)

The Soviets use a vaccine composed of two live but nontoxic strains of the bacillus.

It carries 2,300 live strains and others that are frozen as embryos.

They have also raised the theoretical concern that the vaccine, which consists of a live weakened strain of the chicken pox virus, might itself cause symptoms.

The vaccine contains a live weakened strain of the chicken pox virus that causes an infection that produces no symptoms.

Russia relies on a vaccine made from a live but nonlethal strain of the anthrax bacterium.

The vaccine consists of a live, but attenuated, strain of the yellow fever virus called 17D.

Do not receive vaccines that use live strains of the virus (e.g., measles, mumps, and rubella or MMR) during and for three months following treatment with IGIM.

The article quoted critics as saying that if live strains contaminated the vaccine, the volunteers could be infected.