CVD 103-HgR vaccine for travelers

Dear Editor

The CVD 103-HgR vaccine (Vaxchora), described in “Re-born in the USA: Another cholera vaccine for travellers” by Dr. Freedman, will soon be available to adult travelers to cholera-affected areas [1]. In the United States, most cholera cases reported to the national Cholera and Other Vibrio Illness Surveillance (COVIS) system are associated with travel to cholera-affected areas. In 2011, after the cholera epidemic began in Haiti, 42 cases of laboratory-confirmed cholera were reported [2]. Few cases were reported in 2012 (18), 2013 (14), and 2014 (7). Although cholera is rare in the United States, cases reported to COVIS underestimate the risk to travelers for several reasons. First, cholera is under-reported in the United States, as testing stool specimens for Vibrio cholerae is not routine. Second, although cholera can be life-threatening, illness is usually fairly mild and self-limited, so ill persons may not seek medical care. Third, the incubation period is short, thus many infections likely occur during travel rather than after return to the United States. Such illnesses are not captured by COVIS. Among 90 cases of travel-associated cholera in the United States reported from 2001 to 2011, reasons for travel included visiting friends and relatives (62%), medical missions or other relief work (9%), tourism (7%), and business (7%) [3].

In June 2016, the Advisory Committee on Immunization Practices (ACIP) approved a recommendation for CVD 103- HgR vaccine for adult (18–64 years old) travelers to areas of active cholera transmission [4]. The ACIP considered additional risk factors for travelers to these areas, including increased risk of toxigenic V. cholerae O1 exposure and increased risk of severe outcomes. However, only travel to an area of active cholera transmission was included in the approved recommendation; other risk factors are not mentioned in the recommendation. The proposed definition of an area of active cholera transmission is a province, state, or other administrative subdivision within a country with endemic or epidemic cholera caused by toxigenic V. cholerae O1. It includes areas with cholera activity within the last 1 year that are prone to recurrence of cholera epidemics; it does not include areas where rare sporadic cases have been reported. The vaccine is not routinely recommended for most travelers from the United States, as most travelers from the United States do not visit areas with active cholera transmission. CDC is developing resources for clinicians and travelers to learn which travel destinations may have active cholera transmission.

No information is available about the duration of protection provided by Vaxchora beyond 3–6 months, so the ACIP recommendation does not address reimmunization.