Nonspecific Effects of Oral Polio Vaccine on Diarrheal Burden and Etiology Among Bangladeshi Infants

Main point

Oral Polio Virus may cause nonspecific reductions in mortality by reducing etiology-specific diarrheal burden, specifically the number of days with diarrhea. This is likely driven by reductions in bacterial—especially Campylobacter, Shigella—diarrhea. Similar off-target effects were not identified for rotavirus vaccine.

Abstract

Background.

As the global polio eradication initiative prepares to cease use of oral polio vaccine (OPV) in 2020, there is increasing interest in understanding if oral vaccination provides non-specific immunity to other infections so that the consequences of this transition can be effectively planned for and mitigated.

Methods.

Data were collected from infants in an urban slum in Bangladesh (Mirpur, Dhaka) as part of the performance of rotavirus and oral polio vaccines in developing countries (PROVIDE) study. Following vaccination with trivalent oral polio vaccine (tOPV) at 6, 10, and 14 weeks, infants were randomly assigned to receive tOPV (n = 315) or inactivated polio vaccine (IPV) (n = 299) at 39 weeks. Episodes of diarrhea were documented through clinic visits and twice-weekly house visits through 52 weeks. In sum, 14 pathogens associated with diarrhea were analyzed with TaqMan Array Cards.

Results.

Although the proportion of children experiencing diarrhea was not different between the tOPV and IPV groups ( P = .18), the number of days with diarrhea ( P = .0037) and the number of separate diarrheal episodes ( P = .054) trended lower in the OPV arm. Etiological analysis revealed that male tOPV recipients were less likely to have diarrhea of bacterial etiology ( P = .0099) compared to male IPV recipients but equally likely to experience diarrhea due to viruses ( P = .57) or protozoa ( P = .14). Among the 6 bacterial enteric pathogens tested, only Campylobacter jejuni/ coli detection was significantly reduced in the OPV arm ( P = .0048).

Conclusions.

Our results suggest that OPV may cause nonspecific reductions in mortality, as has been studied elsewhere, by reducing etiology-specific diarrheal burden. This is likely driven by reductions in bacterial diarrhea. Further study of nonspecific OPV effects before global cessation is supported.

Clinical Trials Registration.

NCT01375647.