Can defective interfering RNAs affect the live attenuated influenza vaccine? – Authors’ reply

Reduced effectiveness of LAIV has been observed only in the past 7 years, whereas internal gene components of vaccine viruses that give rise to defective interfering RNAs have remained unchanged since its development. One explanation for the emergence of reduced effectiveness would be a change in the manufacturing process—eg, virus inadvertently being propagated at high multiplicity. Quantification of Ann Arbor LAIV components is currently by focus-forming assay—a convenient method that quantifies virus in a single cycle of replication. This could mistakenly score defective interfering particles as infectious virus. Validation using assays that detect multicycle replication competent virus would be valuable. The presence of defective interfering RNAs in preparations of LAIV from different years and production lines should also be tested. In particular, batches of Leningrad LAIV (manufactured in Russia and India), which uses a different viral genetic background and manufacturing process should be assessed, especially given that low vaccine effectiveness against the pH1N1 component has also been noted in clinical trials with this vaccine.5

Can defective interfering RNAs affect the live attenuated influenza vaccine? – Authors' reply
Source: Virology News