Hepatitis E virus outbreak in postearthquake Nepal: is a vaccine really needed?

Dear Editor, The massive earthquakes that hit Nepal on April 25 and May 12, 2015 claimed more than 8500 lives and displaced more than one million people to temporary shelters. During the recovery period, the monsoon season raised the possibility of significant water borne diseases such as bacterial diarrhoea, typhoid, hepatitis E and cholera. Some experts recommended that the HEV239 vaccine should be used to prevent an outbreak of hepatitis E virus (HEV) infections [1]. In the past, there have been several epidemics of HEV in Nepal – in Kathmandu in 1973, 1981–1982, 1987 and 2006–2007 and Biratnagar in 2014 [2–6] – and 310 HEV-infected pregnant women were documented in those epidemics [2–4]. Repeated epidemics of HEV in the Kathmandu valley may be related to the consumption of contaminated drinking water and the periodic migration of nonimmune people from the endemic areas of the country [5]. Following the earthquake, many predicted that the monsoon would be associated with another epidemic of HEV and suggested that immunization should be introduced. Local residents of the Kathmandu valley have a high prevalence of immunity against HEV (78% of people have IgG antibodies against HEV), whereas people from other cities and nearby areas have a much lower prevalence (25%). Although outbreaks of diarrhoeal and other waterborne diseases are frequent in rural hilly areas, outbreaks of HEV have not been documented in this population, and following the earthquake, there were concerns that an outbreak of HEV may develop. Basnyat et al. projected that nearly 2000 pregnant women in disaster-affected areas might acquire HEV infection with mortality of 500 [1]. However, in our opinion, vaccinating pregnant women (comprising less than 5% of the population) would have little value as the remaining 95% of the displaced population would remain at risk of acquiring HEV. The resulting morbidity and mortality could be substantial among the nonimmune population, and we do not believe that it is justified to ignore them. Furthermore, vaccinating 48 000 pregnant women with three doses on the dawn of monsoon would take six months, and this would make the present vaccination campaign ineffective, at a considerable cost. Vaccination against HEV would clearly not protect recipients from other water borne diseases and might provoke a false sense of security. In our view, safe provision of drinking water alone would be the single most important preventive measure and would be likely to prove cost-effective and generalizable to both pregnant and nonpregnant populations. Rapid and extensive campaigns to ensure safe water at household levels would have a profound impact on prevention and control of HEV outbreaks and should be preferred to vaccination, the safety of which has yet to be established in pregnancy.