Review
Incidence and routes of transmission of hepatitis B virus in England and Wales, 1995–2000: implications for immunisation policy

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Abstract

Background: The incidence of hepatitis B virus (HBV) infection in the UK is low. Since the infection can have serious sequelae, there is a continuing need to examine its epidemiology so as to inform control measures. Objectives: We aimed to describe the current HBV incidence and patterns of transmission in the UK, to estimate the rate of new carrier infections, and to discuss implications for the control of HBV through immunisation. Study design: We analysed routine England and Wales laboratory surveillance data of acute HBV infection (1995–2000) and data on migration and global HBsAg prevalence. Results: The estimated annual incidence of HBV infection in England and Wales was 7.4 per 100,000. Injecting drug use was the most frequently reported route of transmission. The number of cases attributed to heterosexual contact was fairly stable, whereas the number of cases in men having sex with men decreased. These observations continue trends reported for the early 1990s. Transmission during childhood was rarely reported, but was more frequent among South Asians. The incidence in South Asians is relatively high, and their main risk factors are medical treatment overseas and heterosexual contact. For about a third of cases of acute HBV infection no route of transmission is reported, but analysis of secular trends and age distribution suggest that many of these may be related to injecting drug use. Endemic transmission gives rise to only a small proportion of all new chronic infections, with the vast majority arising from immigration of established HBV carriers. Conclusions: The incidence of acute HBV infection in England and Wales has remained low, with a similar pattern of reported routes of transmission compared to the early 1990s. The UK prevalence of HBV infection is dependant on global rather than national immunisation policy. Endemic transmission may be reduced by improving immunisation coverage among injecting drug users, which is expected to also reduce the number of cases without a risk factor reported. In addition, immunisation options that better suit the needs of ethnic minorities need to be explored.

Introduction

The incidence of hepatitis B virus (HBV) infection varies widely between countries, with the estimated life time risk of infection ranging from 0.4% in the UK to over 90% in East Asia (Ramsay et al., 1998, Kane et al., 1993). A likely explanation for this marked difference is that a higher incidence is linked to a lower average age at infection, which has a much higher probability of development of HBV carriage, and therefore of onward transmissions (Edmunds et al., 1996a, Medley et al., 2001).

Although the incidence of infection in England and Wales is amongst the lowest in the world, its potential to cause chronic infection with serious sequelae such as cirrhosis and cancer of the liver means that control of HBV infection is still a public health priority.

Safe and effective vaccines to prevent HBV infection have been available since 1982, and the World Health Organization (WHO) recommended that all countries should have implemented universal immunisation programmes by 1997 (WHO, 1992). However, the current HBV control programme in the UK is based upon selective immunisation of those at highest risk of infection and universal antenatal screening and immunisation of babies born to infected mothers (NHS, 1998, Salisbury and Begg, 1996). The UK strategy is based on the observation that overall incidence of HBV is low, that the risk of infection is distributed heterogeneously in the population (Mortimer and Miller, 1997), and that it is determined mainly by country of birth, ethnicity and adult risk behaviours such as injecting drug use (Soldan et al., 2000, Aweis et al., 2001, Department of Health, 2000).

There is a continuing need to examine the effectiveness of the UK’s HBV vaccination strategy. This is done by analysing current incidence and patterns of transmission. The main source of data for this is the laboratory surveillance of acute HBV infection in England and Wales, complemented by prevalence surveys among groups at different risk of infection. The surveys allow quantification of the burden of infection at a population level, including the many chronic infections acquired prior to immigration into the UK. These latter infections are not preventable by any UK programme, and they limit the potential impact of vaccination on the overall burden of HBV infection.

We have analysed recent routine surveillance data on acute HBV infection in England and Wales, estimated the number of infections imported through immigration, and discuss implications for the control of HBV through immunisation.

Section snippets

Patients and samples

Laboratories in England and Wales routinely report acute HBV infections and associated risk factors to the Health Protection Agency-Communicable Disease Surveillance Centre (HPA-CDSC). A case of acute HBV infection is normally defined by positive serology for HBsAg and anti-HBc IgM, or seroconversion to anti-HBc detected during epidemiological investigation in a person with or without a compatible illness. Cases reported between 1 January 1995 and 31 December 2000 were included in the analyses.

Incidence of acute HBV infection and demographics

Between 1995 and 2000, on average 673 cases of laboratory confirmed acute HBV infection were reported to the HPA-CDSC each year, with a peak of 840 cases in 1998 (Fig. 1). The average incidence of laboratory reports was 1.3 per 100,000 per year, with an incidence rate of 1.6 per 100,000 per year among those aged 15 years or older.

The number of reports represents an estimated total of 3,780 infections per year, resulting in an estimated 269 new chronic infections per year. From this, the true

Discussion

Our analyses of laboratory surveillance of acute HBV infection in England and Wales between 1995 and 2000 suggest that the incidence of HBV has remained at a low level, though with a modest increase in 1998. This increase was mainly due to an increase in the number of cases reported to have resulted from injecting drug use, and a single outbreak linked to autohaemotherapy (Webster et al., 2000).

The cumulative risk of infection at adult age based on our current incidence estimate is similar to

Acknowledgements

We are grateful to all laboratories reporting acute HBV infections, to Usha Gungabissoon and Nigel Gay (HPA-CDSC) and to Rhian Tyler (International Migration Supervisor, ONS).

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