Johns Hopkins Bloomberg School of Public Health researchers say a new candidate vaccine against respiratory syncytial virus (RSV) made with a weakened version of the virus shows great promise at fighting the disease, the leading cause of hospitalization for children under the age of one in the U.S.
There is currently no vaccine against RSV, which causes an estimated 66,000 to 199,000 deaths worldwide each year, and annual wintertime epidemics of respiratory illness in U.S. children.
Creating a vaccine with a live weakened virus – similar to what is used to prevent measles, mumps and rubella – requires a delicate balance: The virus must be weak enough so as not to make anyone sick and strong enough to induce a response from the body’s immune system.
The researchers, who conducted a clinical trial that is reported in the November 4 Science Translational Medicine, say they have used the virus’ own machinery to create a vaccine that may protect young children from RSV disease. The vaccine, called MEDI ΔM2-2, is made from a genetically engineered version of the virus that is missing the gene for the M2-2 protein, a protein that acts like a switch. When M2-2 is deleted, the virus produces more of the viral proteins that trigger immune responses but less of the infectious virus that makes people ill.