Abstract
Background
Various Serosurveys and studies provide ample evidence of differing perspectives regarding epidemiology of HAV and HEV in India. This study was conducted to assess the seroprevalence of HAV and HEV and its associated factors with an aim to provide inputs to planners regarding requirement of HAV vaccine.
Methods
A multi-centric cross sectional survey amongst 4175 healthy trainees (young adults) was carried out in training centres, selected by multistage random sampling, giving equal representation to all regions of India. Sample size was calculated by taking prevalence of HAV seropositivity amongst adults as 60% and alpha 0.05.
Results
Seroprevalence for HAV and HEV was 92.68% (95% CI 91.82, 93.47) and 17.05% (15.90, 18.26), respectively. Logistic regression showed that hand washing without soap, regular close contact with domestic animals, consumption of unpasteurized milk and regular consumption of food outside home were risk factors for HAV (p < 0.05). For HEV, irregular hand washing, consumption of unpasteurized milk and irregular consumption of freshly prepared food were risk factors (p < 0.05).
Conclusion
High level of immunity against HAV among the healthy young adults clearly demonstrates that vaccination against HAV is not required at present in our country. The large proportion being susceptible to HEV points towards the requirement of preventive strategies in the form of safe drinking water supply, hygiene, sanitation, increasing awareness and behaviour change with respect to personal hygiene especially hand and food hygiene.
Keywords: HAV, HEV, Vaccine, Multi-centric survey, Young adults, Trainees
Introduction
Faeco-oral route is one of the leading routes of transmission of infectious diseases and contributes to 4.62 million episodes of diarrhoeal illness worldwide with 1.27 million in SEAR alone.1 1562 DALYs per 100,000 are lost in India due to these infections. Amongst the faeco-orally transmitted pathogens, Hepatitis A and Hepatitis E viruses are responsible for acute viral hepatitis and more than 300 million people worldwide suffer from viral hepatitis annually. Nearly 300 deaths per year are attributed to fulminating acute disease and about 15,000 people succumb each year to chronic liver disease. The disease has an enormous impact on health and national economy of many countries including India.2 Worldwide, Hepatitis A virus (HAV) infection accounts for 1.4 million cases annually with number of cases of HAV in Asian countries ranging from 10 to 30 per 100,000 per year.3 Exact incidence of Hepatitis E virus (HEV) is unknown with outbreaks of HEV common in parts of world with hot climates and rare in temperate climates.4
HAV infection largely depends on sanitary and hygiene conditions of populations. HAV infection in children is generally self-limiting but it causes significant morbidity in adults. Seroprevalence of HAV differs significantly in different socioeconomic groups at 85.3% and 64.5% in upper and lower socioeconomic groups, respectively in an Indian study5 and 68.8% and 79.7% in Bangladesh.6 A study conducted in Delhi has shown seroprevalence of HAV as 57% in individuals less than 35 yrs and 92% in more than 35 yrs with no socioeconomic disparity.7 Lowest seropositivity rates have been reported in Kerala (10.3%) amongst children below 5 yrs of age.8 The available data show heterogeneity among population regarding endemicity of HAV. Epidemics of HAV, mainly affecting young adults have occurred in different parts of the country, e.g. in Delhi,9 Kerala,10,11 Shimla.12
HEV is also self limiting and clinically indistinguishable from other hepatitis infections. Disease affects mainly young adults between 15 and 45 yrs with increased mortality among pregnant women.13 Ratio of clinical to subclinical infection has not yet been determined. Seroprevalence of HEV has been reported to be lower as compared to HAV. Hospital based study among jaundiced patients in a tertiary care hospital in Manipur reported 18% cases due to HEV,14 while a similar study in Pakistan reported the proportion as 5.3%.15 Various epidemics have occurred due to HEV e.g. in Kashmir valley,16 Kanpur17 and Satara district of Maharashtra.18
Armed forces have been no exception to viral hepatitis as it accounted for 4.11% and 3.78% of total hospital admissions during 2005 and 2006 respectively. Average duration of hospital stay was 34.04 and 40.25 days respectively in 2005 and 2006. HAV contributed 0.24 per 1000 hospital admissions while other unspecified viral hepatitis including HEV to 3.37 per 1000 hospital admissions in the year 2006.19 In an Armed Forces study, conducted in a tertiary care hospital with study individuals mainly being army trainees, HAV and HEV have been found to be responsible for 33% and 45.4% cases respectively amongst hepatitis patients.20
Outbreaks as well as sporadic cases of HAV and HEV not only lead to loss of man days but also have a direct effect on fighting efficiency of the troops. Outbreaks of HEV have been reported sporadically from various parts of the country.21,22 Vaccine against HAV is available worldwide to immunize susceptibles and a vaccine against HEV has shown promising results in phase II and III trials.23
Indian Armed forces comprise of men from all regions and socioeconomic status and data on seroprevalence of HAV from the whole country suggests heterogeneity regarding age, socioeconomic status and region while no data are available on HEV in our country so far. Since, no exhaustive study has been carried out either in the armed forces or in the country, this study was conducted to assess the current seroprevalence of Hepatitis A and E infection among young healthy adults joining the Armed Forces, with a view to guide the policy decision on vaccination.
Material and methods
A multi-centric cross sectional survey was conducted in years 2010 and 2011 amongst healthy young adults of eleven (11) training centres, selected by multistage random sampling, giving equal representation to all regions of India.
The purpose and methodology of the study was explained to all study participants and informed consent was obtained. Pretested questionnaire was used to collect data on demographic profile and various risk factors associated with Hepatitis A and E infection. . The participants were asked to answer regarding their practices before joining the training centre. The filled questionnaire and the blood sample of each study participant was coded to relate the results of ELISA later for data entry and analysis.
Briefly, 5 ml of blood was collected under aseptic precautions in red top vacutainer from the cubital vein. The serum was separated and stored in sterile cryovials which was transported to the testing lab in storage boxes, each with capacity of 64 vials. Cold chain was maintained. ELISA for detection of anti-HAV IgG and anti-HEV IgG antibodies was carried out on each of the samples following protocols as per kits manufactured by standard reputed companies. Tests were carried out at the hospitals with ELISA readers nearest to the centres selected.
Sample size was calculated for each centre taking seroprevalence for Hepatitis A as 60%, with alpha 5% and size worked out to be 369 (370) with a total sample size for 11 centres as 4070. Adding 5% for refusals, a total of 4275 participants were included. However, 06 (0.14%) participants in one of the centres gave a probable history of Hep A vaccination and 94 (4.13) were excluded either due to refusal to be part of the study (21) or filling up questionnaire but not providing blood sample (73). A total of 4175 participants were included in the study. Study participants within each centre were chosen by simple random sampling. A data base was created in MS Excel and was analysed using SPSS ver 14.0. 95% confidence intervals were calculated. Chi square test for trend and multivariate analysis were used to analyse the data.
Results
The mean age and sd of study participants were 19.88 years ± 1.38 years. Table 1 depicts the education level, area of residence prior to joining and family income of the study participants. Seroprevalence for IgG antibodies for Hepatitis A virus among the study participants was found to be 92.68% (95% CI: 91.82–93.47) and IgG antibodies for Hepatitis E virus was found to be 17.05% (95% CI: 15.90–18.26). The distribution based on seropositivity for hepatitis A and E has been described in Table 2.
Table 1.
Distribution of Study participants as per age, education, residence and family income.
| N | % | |
|---|---|---|
| Education (N = 4168) | ||
| ≤10th | 191 | 4.58 |
| >10 ≤ 12th | 3940 | 94.53 |
| Graduate and above | 37 | 0.89 |
| Area of residence (N = 4166) | ||
| Rural | 3271 | 78.51 |
| Urban | 895 | 21.49 |
| Family income (N = 4175) | ||
| ≤5000 | 3019 | 72.31 |
| 5001–10000 | 772 | 18.49 |
| 10001–15000 | 95 | 2.27 |
| 15001–20000 | 104 | 2.49 |
| >20000 | 185 | 4.44 |
Table 2.
Distribution of study participants based on Seropositivity for Hepatitis A and E virus.
| Training centre | Station | Presence of IgG antibody [N (%) 95% CI] |
|
|---|---|---|---|
| Against Hepatitis A (n = 3974)a | Against Hepatitis E (n = 3992)b | ||
| I | Ahmadnagar | 372 (97.89) 95.89, 99.09 | 67 (17.63) 13.93, 21.84 |
| II | Bengaluru | 370 (100.00) 99.00, 100.00 | 3 (0.81) 0.17, 02.35 |
| III | Bareilly | 332 (94.05) 91.05, 96.28 | 2 (22.16) 18.03, 26.74 |
| IV | Pune | 373 (92.10) 89.03, 94.53 | 42 (10.34) 07.56, 13.73 |
| V | Jabalpur | 323 (86.83) 82.96, 90.09 | 31 (8.36) 05.75, 11.65 |
| VI | Jabalpur | 315 (86.36) 81.34, 88.81 | 45 (12.20) 09.84, 15.98 |
| VII | Lucknow | 337 (95.74) 93.07, 97.60 | 32 (8.96) 06.21, 12.42 |
| VIII | Namkum | 366 (95.31) 92.69, 97.20 | 21 (5.47) 03.42, 08.24 |
| IX | Pune | 321 (84.25) 80.20, 87.76 | 50 (13.08) 09.87, 16.88 |
| X | Roorkee | 332 (94.05) 91.05, 96.28 | 82 (22.16) 18.03, 26.74 |
| XI | Shillong | 242 (94.90) 91.44, 97.26 | 7 (3.00) 01.22, 06.09 |
| TOTAL | 3683 (92.68) 91.82, 93.47 | 681(17.05) 15.90, 18.26 | |
201 samples for Hep A.
183 for Hep E were either inadequate/haemolysed during processing of blood samples.
The bivariate analysis between various correlates and immunity against HAV and HEV among the study participants was carried out. All the variables showing statistically significant association with immunity to HAV and HEV were included in respective model of multivariate analysis by logistic regression. Results of these models have been depicted in Tables 3 and 4. Logistic regression shows that hand washing without soap, regular close contact with domestic animals, consumption of unpasteurized milk and regular consumption of food outside home were risk factors for HAV (p < 0.05). For HEV, irregular hand washing, consumption of unpasteurized milk and irregular consumption of freshly prepared food were risk factors (p < 0.05).
Table 3.
Multivariate analysis – HAV.
| S No | Variable | Adjusted Odds Ratio | 95% CI |
|---|---|---|---|
| 1 | Hand washing | ||
| With soap | 1 | 1.005, 2.136* | |
| Without soap | 1.465 | ||
| 2 | Domestic animals | ||
| No | 1 | 1.059, 1.938* | |
| Yes | 1.433 | ||
| 3 | Type of milk consumed | ||
| Packaged & pasteurised | 1 | 1.380, 2.965* | |
| Open and unpasteurised | 2.023 | ||
| 4 | Consumption of food outside home | ||
| Infrequently | 1 | 1.856, 10.519* | |
| Frequently | 4.064 | ||
| 5 | Treatment of water | ||
| Boiling | 1 | 0.897, 1.746 | |
| Other | 1.252 | ||
| 6 | Consumption of freshly prepared food | ||
| No | 1 | 0.062, 1.064 | |
| Yes | 0.257 | ||
*p < 0.05.
Table 4.
Multivariate analysis – HEV.
| S No | Variable | Adjusted Odds Ratio | 95% CI |
|---|---|---|---|
| 1 | Hand washing | ||
| Regular | 1 | 1.555, 2.796* | |
| Irregular | 2.085 | ||
| 2 | Type of milk consumed | ||
| Packaged & pasteurised | 1 | 1.385, 3.338* | |
| Open and unpasteurised | 2.166 | ||
| 3 | Consumption of freshly prepared food | ||
| Regularly | 1 | 1.050, 5.731* | |
| Irregularly | 2.454 | ||
| 4 | Hand washing | ||
| With soap | 1 | 0.727, 1.498 | |
| Without soap | 1.043 | ||
| 5 | Domestic animals | ||
| No | 1 | 0.818, 1.390 | |
| Yes | 1.067 | ||
| 6 | Treatment of water | ||
| Boiling | 1 | 0.817, 1.404 | |
| Other | 1.071 | ||
| 7 | Water supply | ||
| Tap | 1 | 0.800, 1.421 | |
| Other sources | 1.066 | ||
| 8 | Place of residence | ||
| Urban | 1 | 0.729, 1.395 | |
| Rural | 1.009 | ||
| 9 | Education status | ||
| >10th | 1 | 0.689, 2.483 | |
| ≤10th | 1.400 | ||
*p < 0.05.
Discussion
The proportion of study participants from rural areas (78.51%) was more in our study as compared to the census figure of 68.85%.24 The seropositivity for HAV shows that approximately 93% of the study participants were immune and only 7.32% were susceptible to hepatitis A virus infection, this is in consonance with the high endemicity zone as per the WHO.25 Our results are also similar to a cross sectional population based study (85.9%) in the age group of 16–25 years.26 Seropositivity rates of around 90% were found in a study conducted on voluntary blood donors aged 18–25 years from city and suburbs of Pune27 and in a population based cross sectional study in Mumbai in age group of 11–30 years.28 However, seroprevalence findings of our study are in contrast to the findings of 54.1% in age group of 15–24 years among healthy outpatients of a hospital in New Delhi8 and 62.6% among medical students of New Delhi in age group of 18–22 years.29 This difference might be attributable to the regional differences, urban – rural differences amongst the study population and also because of different settings of our study and the study conducted in Delhi.
No declining trend of HAV seropositivity was observed when this study findings were compared with earlier studies like a multi-centric study30 in 2001 (80.8% vs 88.30%) and a study in Pune.27 This level of immunity among large proportion of healthy young adults suggests an asymptomatic exposure to HAV. Based on the findings of this study, no epidemiological transition in epidemiology of HAV seems to be taking place.
High level of sero-negativity for anti-HEV shows that large proportion of young adults is susceptible to infection by hepatitis E virus. As per WHO,31 the seroprevalence in our country varies from 10 to 40% and our study has shown a similar pattern with overall being 17.05% (range 15.90–18.26%). A South Indian study32 estimated seroprevalence of 8% among healthy blood donors, antenatal women and patients for elective surgeries aged 16–40 years while a study in Mumbai estimated it as 25.8% in age group of 11–20 years in a residential colony.28
Conclusion
The large proportion of healthy young adults with pre-existing immunity to HAV does not pose risk of personal morbidity and operational ability. The consideration of HAV vaccination as recommended by WHO in this subset of population (healthy young adults) across the country will not only have a tremendous unnecessary economic burden on the meager resources and constrained economy of our country but also an immunological assault on the individuals with pre-existing immunity. Public-health agencies in our country will have to carefully reassess the need for mass or universal vaccination depending on other factors such as the disease burden, available resources and priorities. In view of this high immunity, it would be more pertinent to improve our water supply, sanitation and eating practices rather than recommending vaccine for all. Only after improvements in hygiene, sanitation and water, which may take few years, we can reassess the value of this vaccine in children.
The low seropositivity among healthy young adults shows an increased susceptibility to HEV infection. The risk is increased manifold when conglomeration of individuals takes place in slums, refugee camps, training camps, etc. The dominance of HEV in the whole spectrum of viral hepatitis both sporadically and in outbreaks makes it a suitable candidate for vaccination whenever the same is available. The coordinated efforts towards the research on effectiveness of the candidate vaccine are required but at this juncture preventive strategies aiming at providing clean drinking water, proper sewage disposal and health education in form of hand hygiene practices are of utmost importance. These preventive strategies coupled with efforts to improve housing and living conditions, management of crowds during fairs, festivals, etc., are immediately required for prevention of HEV infection.
Conflicts of interest
All authors have none to declare.
Acknowledgement
This paper is based on Armed Forces Medical Research Committee Project No 3946/2009 granted by the office of the Directorate General Armed Forces Medical Services and Defence Research Development Organisation, Government of India.
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