Changing Epidemiology of Hepatitis A Infection (Commentary) (Clinical Report)
Viral hepatitis continues to be a major public health problem in India. Since the first officially reported epidemic of viral hepatitis in 1955 at Delhi (1), many outbreaks of hepatitis have occurred in different parts of the country (1-3). In India, hepatitis A virus (HAV) is still a major cause of sporadic acute hepatitis (4,5) in children whereas HEV is the major agent for epidemics in adults (3). Most of the outbreaks of waterborne hepatitis in India have been attributed to HEV (1,3), but the epidemiology of viral hepatitis is changing as outbreaks of hepatitis A are being reported with increased frequency, in the paediatric age group as well (2,6,7). Children with HAV tend to present with non-specific gastrointestinal symptoms and jaundice with cholestasis is common. Viral hepatitis A in adults has a more severe course than in children (8,9). In recent years children and adults with acute viral hepatitis A have been reported to have more relapses and a protracted course (9). A study on 37 patients With acute viral hepatitis A (20 children and 17 adults) showed that the mean hospitalization period in adults was longer (28 days as compared with 19), the average serum bilirubin value was higher (5.5 mg/dl as compared with 3 mg/dl), there were more patients with obvious jaundice (59% as compared with 30%) and the serum antibody IgM anti-HAV persisted longer (19 wk as compared with 14 wk). Relapses of the disease were equally frequent (12 vs. 10%), however adults had more often a protracted course of hepatitis (23.5 vs. 10%). The observed differences were not statistically significant (9), suggesting that viral hepatitis A in adults takes a more severe course than in children. Recent changes in the epidemiology of HAV infection and the availability of effective vaccines have renewed interest in this infection. Various studies have shown beyond doubt the increasing seroprevalence rates with age with rates as high as 80.8 per cent in those aged 16 yrs or more (6). Prevalence was lower in the higher socio-economic group (64.5%) compared with the lower socio-economic group (85%) (7). Based on these results, possibility of epidemics of HAV in high socio-economic status population can be predicted wherein HAV vaccination would be of much help. The first recorded outbreak of HAV in Indian adults was from Kottayam, Kerala, and the infection was traced to the presence of a sewage treatment plant which was overflowing and getting mixed with canal water (10). Another study from Delhi over a 5 year period showed an increased incidence of symptomatic HAV among children (10.6 to 22.0%) and also in adults (3.4 to 12.3%) amongst the patients with acute viral hepatitis attending the hospital (11). A study done in Chile showed that routine vaccination of toddlers reduced the rates of symptomatic hepatitis A and associated mortality (12). The two-dose vaccine schedule evaluated in the study was less expensive than disease-related costs in the absence of vaccination from the sixth year of its implementation. These findings supported the establishment of a routine vaccination programme for toddlers in Chile. Routine childhood vaccination against hepatitis A has been introduced in Argentina (13). Inactivated hepatitis A vaccine also demonstrated a good protective effect against an outbreak of hepatitis A in China where vaccination was given after the outbreak in an emergency vaccination campaign (14). A similar study in Israel showed that within 2 wk of starting a mass immunization campaign with hepatitis A vaccine, the incidence of hepatitis A declined dramatically; the last case occurred 6 wk after the immunization programme began and post-exposure administration of immunoglobulin to contacts was ineffective in controlling the outbreak (15). Selective vaccination of the high-risk populations, based on their serological evidence of HAV antibody, could be a rational and cost-effective approach.