Abstract
Severe fever with thrombocytopaenia syndrome (SFTS) is an emerging infectious disease discovered in 2010 and has a case fatality as high as 30%. We intended to study the immune protection conferred by SFTS with natural infection. We collected and analysed 4-year follow-up data to study the characteristics of neutralising antibodies against SFTS virus (SFTSV). The 50% plaque reduction neutralisation test was used for the detection of neutralising antibodies against SFTSV. Geometric mean titres (GMTs) and proportions of patients with a protective titre were analysed, and the persistence of protection was predicted. The titre of antibodies declined yearly in the 4-year study period. Approximately 3 months after infection, the GMT was 143 (95% confidence interval (CI): 89-231), and 100% of patients had a protective titre. In the fourth year, the GMT declined to 53 (95% CI: 37-76), and 95% of patients had a protective titre. The titre was higher in females than in males. On average, the protection offered by neutralising antibodies against SFTSV could last as long as 9 years. The durations of protection were different for different initial titres. The characteristics of neutralising antibodies can be used as a reference for the vaccination doses and schedules of forthcoming vaccines.
Highlights
Severe fever with thrombocytopaenia syndrome (SFTS) is an emerging infectious disease discovered in China in 2010 [1]
The generalised estimating equation (GEE) is a general statistical approach to fit a marginal model for longitudinal data analysis, and it has been popularly applied to clinical trials and biomedical studies [4, 5]
The neutralising antibody titre against SFTS virus (SFTSV) was measured by standard plaque reduction neutralisation test
Summary
Severe fever with thrombocytopaenia syndrome (SFTS) is an emerging infectious disease discovered in China in 2010 [1]. A safe and efficacious vaccine may be a good option. There are no vaccines available on the market . Information about the characteristics of immunity to SFTS is still scarce as it is a newly discovered disease. We conducted a follow-up study from 2011 to 2015 to study the decay of neutralising antibodies against SFTS virus (SFTSV). After the study period of 4 years, all 25 patients still maintained neutralising antibodies, which indicated long-term persistence of neutralising antibodies against SFTSV. We further analysed the 4-year follow-up data to learn about the long-term persistence and the differences of neutralising antibodies against SFTSV between the gender and age of patients. The generalised estimating equation (GEE) is a general statistical approach to fit a marginal model for longitudinal data analysis, and it has been popularly applied to clinical trials and biomedical studies [4, 5]
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