Persistence Of Immune Responses To Vaccine Against Haemorrhagic Fever With Renal Syndrome In Healthy Adults Aged 16-60 Years: Results From An Open-Label 2-Year Follow-Up Study

Background: Approximately 2 million doses of vaccine against haemorrhagic fever with renal syndrome (HFRS) have been used annually in China. However, there were limited studies focused on persistence of immune responses to HFRS vaccine in healthy adults. A phase 4, multicentre, open trial has been undertaken to assess antibody persistence after HFRS vaccination of healthy adolescents and adults aged 16-60 years.Methods: The vaccine was administered as a three-dose series at 0, 2 weeks and 6 months, including two primary doses and one booster dose. Anti-hantavirus IgG antibodies were measured by enzyme-linked immunosorbent test (ELISA) pre-vaccination and 1.5, 7 and 24 months after the initial vaccination.Results: A total of 143 individuals aged 16-60 years were included. The median OD (range) values of IgG antibody were 0.005 (0.004-0.016), 0.116 (0.036-0.620), 0.320 (0.065-0.848) and 0.128 (0.011-0.649) pre-vaccination and at 1 month after the two primary doses, 1 month after the booster dose and 18 months after the booster dose. The positivity rate was 7.7%, 40.6%, 62.2% and 48.2%, respectively.Conclusions: The two primary doses could help healthy individuals to generate an immune response, and this three-dose series may be better than a two-dose regimen.