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.

Hydroclimatic drivers of highly seasonal leptospirosis incidence suggest prominent soil reservoir of pathogenic Leptospira spp. in rural western China

“…Sichuan shared in China's long-term trend towards decreasing leptospirosis incidence [26,47]. A number of explanations have been put forward to explain the long-term decrease in reported leptospirosis over time in China, including improvements in sanitation, vaccination campaigns of high-risk populations [48], mechanization of agriculture, and the inclusion of antibiotics active against leptospires in commercial feeds for captive-bred pigs [47,49]. Examination of reported cases in Sichuan extending back to 1990 reveals a continual downward trend in leptospirosis which the 2004-2005 data seem to align with (S2 Text), thus it does not appear that 2004-2005 were abnormal years, either with respect to surveillance (the NIDRS was established in 2004), or disease occurrence.…”

Genetic diversity of Leptospira interrogans circulating isolates and vaccine strains in China from 1954–2014

“…Furthermore, of 34 Chinese serogroup reference strains represented the diversity revealed by serogroup typing of > 300 isolates. 13 Thus, these strains used should provide a good representation of geographic and genetic diversity of L. interrogans population in China.…”

“…An inactivated whole-cell vaccine including seven major L. interrogans serogroups is still used in the Chinese Expanded Program on Immunization. 11,13 Not surprising, seven vaccine strains have different MT, which were different from other circulating isolates. It is possibly associated with these vaccine strains belonged to old circulating isolates and replaced by new type isolates.…”

“…Furthermore, considering the short-lived serogroup-specific immunity acquired from current inactivated vaccines, it is necessary to develop a universal recombinant leptospirosis vaccine. 13 The data of genotyping for circulating isolates and vaccine strains will contribute to the choices of vaccine strain and efficacy evaluation of leptospirosis vaccine product.…”

“…11,13 Three highly virulent (serogroups Icterohaemorrhagiae, Grippotyphosa, and Autumnalis) and four low-virulence strains (serogroups Canicola, Pomona, Australis, and Hebdomadis) are used as vaccine strains, which are the major L. interrogans serogroups and covered more than 80 % serogroup coverage of circulating strains in the country. 13 Considering the inherent sidereactions and serogroup-specific immunity from inactivated vaccines, it is suggested that universal recombinant vaccines should be developed in the future. Meanwhile, it is curial to select the appropriated vaccine strains for understand the genetic diversity of Leptospira isolates and vaccine strains.…”