Human leptospirosis vaccines in China

Abstract

The present incidence of leptospirosis in China is significantly lower than past rates, although small localized outbreaks continue to occur in epidemic regions. Improvements in sanitation, as well as vaccination of high-risk populations, have played crucial roles in reducing the disease burden. Several types of human leptospirosis vaccines have been developed, including inactivated whole-cell, outer-envelope, and recombinant vaccines. Of these, only a multivalent inactivated leptospirosis vaccine is available in China, which was added to the Chinese Expanded Program on Immunization in 2007. However, this vaccine elicits serogroup-specific immunity, and serogroup epidemiology should continue to be monitored to enhance vaccine coverage and distribution. On the other hand, the efficiency of the inactivated vaccine should be further improved by optimizing the formulation, and by expanding the target population. More importantly, additional investments should be made to develop universal recombinant vaccines.

Keywords: human vaccines; inactivated whole-cell vaccine; leptospirosis; recombinant vaccine.

Figure 1.

Reported leptospirosis cases and mortality in China in 1987–2016. The red columns and blue line represent the annual reported cases and disease mortality, respectively.

Figure 2.

Four regions with different leptospirosis incidence and geographical locations in China.^, The A region (pink) is located in tropical or subtropical areas, where typhoons commonly occur, and it has moderate incidence. The B region (red), in which incidence is the highest, encompasses 13 provinces such as Sichuan, Yunan, Zhejiang, Jiangxi, Fujian and Anhui, and is located in the middle and lower Yangtze River regions. The C region (gray) comprises the temperate region located in the middle and lower areas of the Yellow River, with lower leptospirosis incidence. Meanwhile, no human leptospirosis has been reported in the D region (white), which has a dry climate.