Enterotoxigenic E. coli (ETEC) is a type of bacteria that can infect both children and adults, causing diarrhoea. In particular, it affects people in developing countries. However, it is also a major cause of 'travellers' diarrhoea' in people visiting or returning from regions where this infection is common. It is transmitted from person to person by eating or drinking unclean food or water. Typically it causes watery diarrhoea, with abdominal pains and vomiting, that can last for several days. Vaccines are being considered as a way to prevent diarrhoea caused by ETEC bacteria. ETEC bacteria share some similarities with the bacteria that cause cholera. In this review, we examined the effectiveness of either vaccines designed to prevent cholera or vaccines designed specifically to prevent ETEC infection for preventing ETEC diarrhoea. We compared these vaccines against the use of a control vaccine (either an inert vaccine or a vaccine normally given to prevent an unrelated infection), no intervention, an alternative ETEC vaccine, or a different dose or schedule of the same ETEC vaccine.
We examined the research published up to 07 December 2012. We included 24 randomized controlled trials and 53,247 participants in this review. Four studies assessed the use of oral cholera vaccines to prevent diarrhoea caused by ETEC and eight trials assessed the use of ETEC-specific vaccines to prevent diarrhoea. Seven studies presented data from field trials and four studies presented data from studies where people were artificially infected with ETEC bacteria. Also, 13 trials gave safety and immunological data only.
There is currently insufficient evidence to support the use of the oral cholera vaccine Dukoral® to protect travellers against ETEC diarrhoea. Based on a single trial in people travelling from the USA to Mexico, the oral cholera vaccine Dukoral® may have little or no effect in preventing ETEC diarrhoea (one trial, 502 participants, low quality evidence). Two earlier trials, one undertaken in an endemic population in Bangladesh and one undertaken in people travelling from Finland to Morocco, evaluated a precursor of the oral cholera vaccine Dukoral®. Short term protection against ETEC diarrhoea was demonstrated, lasting for around three months (RR 0.43, 95% CI 0.26 to 0.71; two trials, 50,227 participants). However, this vaccine is no longer available.
An ETEC-specific, killed whole cell vaccine, which also contains the recombinant cholera toxin B-subunit, was evaluated in people travelling from the USA to Mexico or Guatemala, and from Austria to Latin America, Africa, or Asia. There were no statistically significant differences in ETEC-specific diarrhoea or all-cause diarrhoea (two trials, 799 participants) found and the vaccine was associated with increased vomiting (RR 2.0, 95% CI 1.16 to 3.45; nine trials, 1528 participants). The other ETEC-specific vaccines in development have not yet demonstrated clinically important benefits. Further research is needed to develop safe and effective vaccines to provide both short and long-term protection against ETEC diarrhoea.