Control of a community-wide outbreak of hepatitis A by mass vaccination with inactivated hepatitis A vaccine

Homelessness and Hepatitis A-San Diego County, 2016-2018

BACKGROUND

Hepatitis A is a vaccine-preventable viral disease transmitted by the fecal-oral route. During 2016-2018, the County of San Diego investigated an outbreak of hepatitis A infections primarily among people experiencing homelessness (PEH) to identify risk factors and support control measures. At the time of the outbreak, homelessness was not recognized as an independent risk factor for the disease.

METHODS

We tested the association between homelessness and infection with hepatitis A virus (HAV) using a test-negative study design comparing patients with laboratory-confirmed hepatitis A with control subjects who tested negative for HAV infection. We assessed risk factors for severe hepatitis A disease outcomes, including hospitalization and death, using multivariable logistic regression. We measured the frequency of indications for hepatitis A vaccination according to Advisory Committee on Immunization Practices (ACIP) guidelines.

RESULTS

Among 589 outbreak-associated cases reported, 291 (49%) occurred among PEH. Compared with those who were not homeless, PEH had 3.3 (95% confidence interval [CI], 1.5-7.9) times higher odds of HAV infection, 2.5 (95% CI, 1.7-3.9) times higher odds of hospitalization, and 3.9 (95% CI, 1.1-16.9) times higher odds of death associated with hepatitis A. Among PEH, 212 (73%) patients recorded other ACIP indications for hepatitis A vaccination.

CONCLUSIONS

PEH were at higher risk of infection with HAV and of severe hepatitis A disease outcomes compared with those not experiencing homelessness. Approximately one-fourth of PEH had no other ACIP indication for hepatitis A vaccination. These findings support the recent ACIP recommendation to add homelessness as an indication for hepatitis A vaccination.

Vaccination strategies for control of community outbreaks of hepatitis A: A comparison of two outbreaks in England

In August 2015 two community outbreaks of hepatitis A virus (HAV) occurred in sub-urban communities in Northern England. Each was managed by an independent outbreak control team. In outbreak one, mass vaccination was deployed targeting a residential area and two schools, while in outbreak two, vaccination was reserved for household-type contacts of cases. The highest vaccination uptake was achieved in the school settings (82% and 95%). These case studies illustrate the range of approaches that can be used and the factors that influence decision-making in response to a hepatitis A community outbreak. Both outbreaks likely started from importation(s) of HAV by returning travellers and spread through extended social networks and the local community. Vaccination strategies were selected based on hypotheses about transmission pathways, which were informed by evidence from oral fluid (OF) testing of asymptomatic contacts. More evidence about the effectiveness of mass vaccination in community outbreaks of hepatitis A in low endemicity settings is needed. Hepatitis A guidelines should include recommendations for the use of mass vaccination and OF testing in outbreaks.

Immunization against Hepatitis A

Worldwide, there are multiple formaldehyde-inactivated and at least two live attenuated hepatitis A vaccines now in clinical use. The impressive immunogenicity of inactivated vaccines is reflected in rapid seroconversion rates, enabling both preexposure and postexposure prophylaxis. Universal childhood vaccination programs targeting young children have led to significant drops in the incidence of hepatitis A both in toddlers and in susceptible nonimmune adults in regions with intermediate endemicity for hepatitis A. Although the safety of inactivated vaccines is well established, further studies are needed concerning the implications of fecal virus shedding by recipients of attenuated vaccines, as well as the long-term persistence of immune memory in children receiving novel immunization schedules consisting of single doses of inactivated vaccines.

Long-term immunogenicity and immune persistence of live attenuated and inactivated hepatitis a vaccines: a report on additional observations from a phase IV study

Both live attenuated (HA-L) and inactivated (HA-I) hepatitis A vaccine were licensed for routine use in China. Although phase 1, 2 and 3 clinical studies of both vaccines have been completed, further systematic evaluation of their immunogenicity and immunological persistence under phase 4 clinical studies in a wide range of conditions and involving large populations is necessary. A phase IV clinical trial (NCT02601040) was performed in 9000 participants over 18 months of age. Geometric mean concentrations (GMCs) and seroconversion rates (SRs) were compared at five time points during 3 years for 1800 individuals among them. The SRs of HA-L and HA-I were 98.08% (95% CI 95.59%-99.38%) and 99.64% (95% CI 98.93%-100.00%) respectively 28 days after administration of the first dose, and remained at 97.07% (95% CI 94.31%-98.73%) or above and 96.73% (95% CI 94.07%-98.42%) or above respectively during the following 3 years. The GMCs for both the HA-L and HA-I groups showed that both vaccines elicited high anti-HAV titres, considerably more than the threshold of protection needed against HAV infection in humans, and these titres were sustained. Hence, both HA-I and HA-L vaccines could provide an excellent long-term protective effect, and supported the routine use of both vaccines.

An extra priming dose of hepatitis A vaccine to adult patients with rheumatoid arthritis and drug induced immunosuppression - A prospective, open-label, multi-center study

BACKGROUND

Previous studies have indicated that a pre-travel single dose of hepatitis A vaccine is not sufficient as protection against hepatitis A in immunocompromised travelers. We evaluated if an extra dose of hepatitis A vaccine given shortly prior to traveling ensures seroconversion.

METHOD

Patients with rheumatoid arthritis (n = 69, median age = 55 years) treated with Tumor Necrosis Factor inhibitor(TNFi) and/or Methotrexate (MTX) were immunized with two doses of hepatitis A vaccine, either as double dose or four weeks apart, followed by a booster dose at six months. Furthermore, 48 healthy individuals, median age = 60 years were immunized with two doses, six months apart. Anti-hepatitis A antibodies were measured at 0, 1, 2, 6, 7 and 12 months.

RESULTS

Two months after the initial vaccination, 88% of the RA patients had protective antibodies, compared to 85% of the healthy individuals. There was no significant difference between the two vaccine schedules. At twelve months, 99% of RA patients and 100% of healthy individuals had seroprotective antibodies.

CONCLUSION

An extra priming dos of hepatitis A vaccine prior to traveling offered an acceptable protection in individuals treated with TNFi and/or MTX. This constitutes an attractive pre-travel solution to this vulnerable group of patients.

Type A viral hepatitis: A summary and update on the molecular virology, epidemiology, pathogenesis and prevention

Although epidemic jaundice was well known to physicians of antiquity, it is only in recent years that medical science has begun to unravel the origins of hepatitis A virus (HAV) and the unique pathobiology underlying acute hepatitis A in humans. Improvements in sanitation and the successful development of highly efficacious vaccines have markedly reduced the worldwide prevalence and incidence of this enterically-transmitted infection over the past quarter century, yet the virus persists in vulnerable populations and remains a common cause of food-borne disease outbreaks in economically-advantaged societies. Reductions in the prevalence of HAV have led to increases in the median age at which infection occurs, often resulting in more severe disease in affected persons and paradoxical increases in disease burden in some developing nations. Here, we summarize recent advances in the molecular virology of HAV, an atypical member of the Picornaviridae family, survey what is known of the pathogenesis of hepatitis A in humans and the host-pathogen interactions that typify the infection, and review medical and public health aspects of immunisation and disease prevention.

Effectiveness of hepatitis A vaccination as post-exposure prophylaxis

Hepatitis A (HA) has been a vaccine-preventable disease since 1995. In Catalonia, a universal combined hepatitis A+B vaccination program of preadolescents was initiated at the end of 1998. However, outbreaks are reported each year and post-exposure prophylaxis (PEP) with hepatitis A virus (HAV) vaccine or immunoglobulin (IG) is recommended to avoid cases. The aim of this study was to assess the effectiveness of HAV vaccine and IG in preventing hepatitis A cases in susceptible exposed people. A retrospective cohort study of contacts of HA cases involved in outbreaks reported in Catalonia between January 2006 and December 2012 was made. The rate ratios and 95% confidence intervals (CI) of HA in susceptible contacts receiving HAV or IG versus those without PEP were calculated. There were 3550 exposed persons in the outbreaks studied: 2381 received one dose of HAV vaccine (Hepatitis A or hepatitis A+B), 190 received IG, and 611 received no PEP. 368 exposed subjects received one dose of HAV vaccine and IG simultaneously and were excluded from the study. The effectiveness of PEP was 97.6% (95% CI 96.2-98.6) for HAV vaccine and 98.3% (95% CI 91.3-99.9) for IG; the differences were not statistically significant (p = 0.36). The elevated effectiveness of HAV vaccination for PEP in HA outbreaks, similar to that of IG, and the long-term protection of active immunization, supports the preferential use of vaccination to avoid secondary cases.

Viral hepatitis: global goals for vaccination

In countries where hepatitis A is highly endemic, exposure to hepatitis A virus (HAV) is almost universal before the age of 10 years, and large-scale immunization efforts are not required. In contrast, in areas of intermediate endemicity or in transition from high to intermediate endemicity, where transmission occurs primarily from person to person in the general community (often with periodic outbreaks), control of hepatitis A may be achieved through widespread vaccination programmes. Hepatitis B virus (HBV) is one of the world's most widespread infectious agents and the cause of millions of infections each year. Between 500,000 and 700,000 people die each year from chronic infection-related cirrhosis, hepatocellular carcinoma (HCC) or from acute hepatitis B. Hepatitis B vaccine provides protection against infection and its complications including liver cirrhosis and HCC. It is therefore, the first vaccine against a cancer, the first vaccine protecting from a sexually transmitted infection, and the first vaccine against a chronic disease ever licensed. Control and significant reduction in incidence of new HBV infections as well as hepatocellular carcinoma has repeatedly been reported in countries in East Asia (i.e. Taiwan) and Africa (i.e. The Gambia). Two experimental vaccines against hepatitis E have been developed; one of them has been recently licensed but is not yet widely available. Attempts to develop a hepatitis C vaccine were so far unsuccessful.

[Community outbreak of hepatitis A in a marginal population. Vaccination for its control and acceptance of the measure]

OBJECTIVE

To study a community outbreak of hepatitis A in a marginal population and the public health response in order to bring it under control.

DESIGN

Descriptive study of the outbreak that occurred in February-June, 2004. An epidemiological survey was conducted to detect prior cases and active vigilance was set up. Case and susceptibility definitions were established.

SETTING

A gypsy population in Madrid, Spain. They had basic provision of sewerage, water supply and waste disposal.

PARTICIPANTS

A population of 550 in census; estimated population, 800. 70% were under 40 and 55% were illiterate.

INTERVENTIONS

Control measures were: a) health education activities to strengthen habits of hygiene, and b) immunisation of susceptible individuals. A total of 646 people were vaccinated, with the active help of staff from the Institute of Rehousing and Integration into Society.

RESULTS

The outbreak affected 26 people, with an average age of 8 (95% CI, 6.2-9.8), similar distribution by sex and 3.3% attack rate. Fourteen cases were students at state schools, not all in the same classes. There were 7 pairs of siblings among the cases. The diagnosis was conformed by serology in 17 cases. Five needed hospital admission.

CONCLUSIONS

The epidemic curve suggested person-person transmission. All those affected were under 20 years old. Vaccination was seen to be effective in controlling the outbreak. Interventions were assisted by intermediaries in order to respect the gypsies' cultural context and were well accepted.

The cost-effectiveness of universal vaccination of children against hepatitis A in Argentina: results of a dynamic health-economic analysis

BACKGROUND

Socioeconomic improvements can reduce levels of endemic hepatitis A, but conversely increase the burden of disease. Routine childhood vaccination can rapidly control hepatitis A infection rates through the induction of herd immunity, although such programs can be costly.

METHODS

We evaluated the healthcare benefits and cost-effectiveness of a routine childhood vaccination program against hepatitis A in Argentina, using a dynamic model that incorporated the changing epidemiology of infection and the impact of vaccine-induced herd immunity. Demographic, disease, and economic data from Argentina were used where available.

RESULTS

At 95% coverage, the program would reduce the number of hepatitis A infections by 352,405 annually, avoiding 121,587 symptomatic cases and 428 deaths. Substantial healthcare benefits were also observed with vaccination coverage as low as 70%, which would prevent 295,826 infections. Economically, the program would save 23,989,963 US$ annually at 95% coverage, equivalent to 3,429 US$ per life-year gained. The program remained cost-saving in response to variation in factors, including disease-related costs, discount rate, herd immunity level, and rate of decrease of force of infection. The break-even cost per vaccine dose for the society was 25 US$ in the base-case, more than three times the current public cost of 7 US$ per dose.

CONCLUSIONS

Routine childhood vaccination against hepatitis A showed both health benefits and robust economic benefits in this analysis, supporting the recent decision of the Argentine government to implement such a program.

Universal mass vaccination against hepatitis A

When first introduced in 1992 the hepatitis A vaccine was recommended for individuals at high risk of exposure. This policy was not expected to have a significant impact on disease incidence at population level in view of the epidemiology of the hepatitis A virus (HAV). More recently two countries, Israel and Bahrain, and regions or subpopulations in others (Australia, China, Byelorussia, Italy, Spain, US) have embarked upon more ambitious vaccination programmes that aim to immunize whole birth cohorts. After a brief survey of the virology and epidemiology of HAV, the disease burden it inflicts and a short history of the development of HAV vaccines--both live (in China) and killed vaccines are available--he vaccination programmes introduced in the countries mentioned above are described. The results have been spectacular: disease incidence, not only in the vaccinated cohorts but also in the whole population, have plummeted within a few years of the start of mass vaccination. There is now convincing evidence that the vaccine confers herd immunity if the main spreaders of the virus are targeted for immunization. This finding should encourage other countries to start mass vaccination programmes against HAV, particularly as pharmacoeconomic studies are beginning to show that such a strategy could be a cost-effective way of controlling the disease. It is now even conceivable to eradicate HAV. In fact, this should be easier to achieve than polio eradication as HAV vaccines confer more durable immunity than polio vaccines. However, the global disease burden of HAV is generally thought not to be high enough to justify such an undertaking in the foreseeable future.

A novel process for production of hepatitis A virus in Vero cells grown on microcarriers in bioreactor

AIM: To develop a novel process for production of HAV in Vero cells grown on microcarriers in a bioreactor.

METHODS: Vero cells infected with HAV strain W were seeded at an initial density of 1 × 10⁵ cells/mL into a 7-L bioreactor containing Cytodex-I microcarriers. During the stage of cell proliferation, the following conditions were applied: pH7.2 ± 0.2, temperature 37 ± 0.2 °C, dissolved oxygen 40% of air saturation and agitation rate 40 r/min . After the stage of virus culture started, the culture conditions were altered to pH7.2 ± 0.2, temperature 35 ± 0.2 °C, dissolved oxygen 25% of air saturation, agitation rate 50 r/min and perfusion of fresh medium at a flux of 20 mL/h. During the course of fermentation, cell density, HAV antigen titre, glucose, lactate and ammonia levels were monitored. A control experiment using conventional static culture was conducted in the T150 flask.

RESULTS: After a 28-d cultivation, cell density increased to 14.0 × 10⁵ cells/mL in the bioreactor, 5.6 × 10⁹ viable cells and 4000 mL virus suspension with a titre of 1:64 were harvested. The viral antigen output per cell unit in the bioreactor was 3-fold higher than that in the T150 flask. Meanwhile the metabolic mode of Vero cells did not change after the infection with HAV strain W.

CONCLUSION: The process for production of HAV in Vero cells grown on microcarriers in a bioreactor is a novel, efficient and practical way to obtain virus antigen for vaccine purpose. This approach produces more cells and HAV antigen than the conventional static culture. With futher improvement, it is possible to be used for the production of hepatitis A vaccine.

[Hepatitis A outbreak in a day care center and household transmission]

BACKGROUND

An outbreak of hepatitis A occurred in a day care center in Madrid between October 2002 and February 2003 and spread to the children's families.

PATIENTS AND METHODS

We performed a descriptive study of this outbreak and of the control measures adopted.

RESULTS

The outbreak affected 23 people: eight children aged 1-3 years (attack rate= 8.7 %), two staff members (attack rate=10.5 %), and 13 household contacts. Of the 23 cases, 17 were confirmed by serology and eight patients were hospitalized. The control measures were: (i) increasing general hygiene measures in the home and school and, in particular, those concerning diaper changing by staff, and (ii) vaccination of all pupils aged more than one year (92 children), staff members (16 adults) and family contacts of affected individuals. After vaccination, the epidemic curve showed intrafamilial transmission exclusively. Cases among familial contacts affected adults in contact with asymptomatic children.

CONCLUSIONS

Vaccination was effective in controlling the epidemic outbreak within the day care center. However, when outbreaks occur, vaccination should be prescribed to close contacts of all the children, whether symptomatic or not, especially parents and siblings. The recommendation that day care center workers undergo vaccination on taking up their posts should be put into practice, since vaccination is not systematically performed. General vaccination would be the most effective measure for preventing outbreaks in educational centers.

The role of vaccine in controlling hepatitis A epidemics

We report the conduct and results of a review of recent literature to describe various types of epidemics and outbreaks in Italy or countries with similar epidemiological profiles and to assess vaccine use in outbreak situations. We identified three scenarios most likely to occur in Italy: outbreaks occurring in small closed communities (nursery or a primary school), outbreaks in communities of limited dimensions (small towns or villages) and open community settings in which epidemics occur at regular intervals (person-to-person transmission). In closed communities we recommend vaccination of family members and school personnel living or working in close proximity to the index case as well as classmates. We also recommend vaccination when there is a proof of secondary transmission within the community. In small open communities we recommend vaccination of more susceptible age groups such as children and adolescents. For large open communities the only practicable alternative strategy is vaccination of close family contacts of acute cases couple with non-immunity boosting control measures.

Hepatitis a outbreak in a public school in Rio de Janeiro, Brazil

From June 1 to July 1 1999, an outbreak involving 25 cases of hepatitis A occurred in a public school in Rio de Janeiro, Brazil. Since these cases were notified to the State Health Department, the National Reference Center for Hepatitis Viruses (CNRHV) was required to investigate the extent of hepatitis A virus (HAV) dissemination. Blood samples from all students were tested for IgM and total anti-HAV antibodies using a commercial enzyme-linked immunoassay (ELISA). At the same time, a questionnaire was completed in order to identify possible risk factors for HAV infection. The environmental investigation showed that there was no fecal contamination of the water supply. The epidemiological investigation demonstrated that almost 50% of this population was susceptible to HAV infection and probably person-to-person transmission was the principal mode of virus dissemination. In this situation, a massive vaccination campaign could control the HAV infection.