Antibodies in lymphocyte supernatants can distinguish between neutralising antibodies induced by RSV vaccination and pre-existing antibodies induced by natural infection.

There was a wide background distribution of RSV-specific antibodies in serum and nasal samples that obscured vaccine-specific responses measured two weeks after vaccination. No RSV-specific antibodies were observed at baseline in ALS samples, but a clear vaccine-specific antibody response was observed in ALS seven days after the administration of each dose of vaccine. These vaccine-specific antibodies in ALS displayed functional activity in vitro, and quantification of this functional activity was unperturbed by pre-existing antibodies from natural exposure. The results demonstrate a promising new approach for assessing functional immune responses attributed to RSV vaccines.