Vaccines against enteric infections for the developing world

Abstract

Since the first licensure of the Sabin oral polio vaccine more than 50 years ago, only eight enteric vaccines have been licensed for four disease indications, and all are given orally. While mucosal vaccines offer programmatically attractive tools for facilitating vaccine deployment, their development remains hampered by several factors: -limited knowledge regarding the properties of the gut immune system during early life; -lack of mucosal adjuvants, limiting mucosal vaccine development to live-attenuated or killed whole virus and bacterial vaccines; -lack of correlates/surrogates of mucosal immune protection; and -limited knowledge of the factors contributing to oral vaccine underperformance in children from developing countries. There are now reasons to believe that the development of safe and effective mucosal adjuvants and of programmatically sound intervention strategies could enhance the efficacy of current and next-generation enteric vaccines, especially in lesser developed countries which are often co-endemic for enteric infections and malnutrition. These vaccines must be safe and affordable for the world's poorest, confer long-term protection and herd immunity, and must be able to contain epidemics.

Keywords: developing country; enteric; gut; immunity; mucosa; vaccine.

Figure 1.

Incidence of enteric infections caused by different pathogens in children below 5 years of age (GEMS study data adapted from Kotloff et al. [3] show attributable pathogen-specific incidence per 100 child years). (Online version in colour.)

Figure 2.

Summary of protective efficacies of Dukoral and Shanchol in large field trials in Bangladesh 1985–1988 (Dukoral) and India 2006–2009 (Shanchol). Data adapted from [27,28] (PEs for Dukoral are based on whole population assuming same PE in adult males as in women).