5 Undersøgelser, der er gennemført under den kliniske udvikling af denne vaccine, har vist, at immuniteten over for de stammer, der er inkluderet i vaccinen, normalt persisterer 6- 12 måneder efter vaccinationen.
The persistence of postvaccination antibodies to strains included in the vaccine is usually 6-12 months, as shown by studies performed during the clinical development of this vaccine.