Cell mediated and antibody immune response to inactivated hepatitis A vaccine

Persistence of immunity against hepatitis A in Brazilian children vaccinated with a single dose of inactivated virus vaccine

In 2014, the Brazilian National Immunization Program implemented the universal vaccination against the hepatitis A virus (HAV) for children aged 12 months and older, applying a single dose of the inactivated virus vaccine. It is essential to carry out follow-up studies in this population, aiming to verify the longevity of HAV immunological memory. This study evaluated the humoral and cellular immune response of a cohort of children vaccinated between 2014 and 2015, and further investigated between 2015 and 2016, and who had their initial antibody response assessed after the single dose. A second evaluation took place in January 2022. We examined 109 children out of the 252 that took part in the initial cohort. Seventy (64.2%) of them had anti-HAV IgG antibodies. Cellular immune response assays were performed in 37 anti-HAV-negative and 30 anti-HAV-positive children. Production of interferon-gamma (IFN-y) stimulated with the VP1 antigen was demonstrated in 34.3% of these 67 samples. Of the 37 negative anti-HAV samples, 12 (32.4%) produced IFN-y. Among the 30 anti-HAV-positive, 11 (36.7%) produced IFN-y. In total, 82 (76.6%) children presented some type of immune response against HAV. These findings demonstrate the persistence of immunological memory against HAV in the majority of children vaccinated between 6 and 7 years with a single dose of the inactivated virus vaccine.

Humoral and cellular immune memory response 12 years following single dose vaccination against hepatitis A in Argentinian children

Infants' universal hepatitis A virus (HAV) single-dose vaccination has been highly effective for controlling HAV infection in Argentina, and in other Latin-American countries that adopted that strategy. Although antibodies wane over time, this has not been associated with HAV outbreaks or breakthrough infections, suggesting a relevant role for memory immunity. This study assessed long term humoral and cellular immune memory response after an average of 12 years follow-up of HAV single-dose vaccination. We selected 81 HAV-single dose vaccinated individuals from a 2015 study, including 54 with unprotective (UAL) and 27 with protective antibody levels (PAL) against HAV. Humoral memory response was assessed by measuring anti-HAV antibody titers at admission in both groups, and 30 days after a booster dose in the UAL group. Flow cytometry analysis of peripheral blood mononuclear cell samples stimulated with HAV antigen was performed in 47/81 individuals (21 with PAL, 26 with UAL) to identify activated CD4 + memory T cells or CD8 + memory T cells. The results showed that 48/52 (92%) individuals from UAL group who completed follow up reached protective levels after booster dose. In the PAL group, anti-HAV Abs waned in 2/27 (7%) individuals lacking seroprotection, while in 25/27 (93%) Abs remained >10 mUI/mL. HAV-specific memory CD4 + T cells were detected in 25/47 (53.2%) subjects while HAV-specific memory CD8 + T cells were observed in 16/47 (34.04%) individuals. HAV-specific memory CD4⁺ and CD8⁺ T cell responses were detected in 11/21 (52.4%) and in 9/21 (42.9%) subjects with PAL and in 14/26 (53.8%) and in 7/26 (26.9%) individuals with UAL, showing that the presence of memory T-cells was independent of the level or presence of anti-HAV antibodies. Long-term immunity demonstrated in the present work, including or not antibody persistence, suggests that individuals with waned Ab titers may still be protected and supports the single-dose HAV strategy.

Long-Term Persistence of Antibody Response with Two Doses of Inactivated Hepatitis A Vaccine in Children

INTRODUCTION

Hepatitis A virus infection is more severe in adults than children. Although vaccination can protect adults, current childhood programs cover a large population more successfully. Childhood vaccination is, therefore, a solution to protecting adults if it induces lasting immunity. Fifteen-year protection has been demonstrated in children, but longer-term data are only available for adults. We aimed to predict long term persistence of antibody in children beyond 15 years and assess if immunological mechanisms triggered by vaccination support longer-term protection.

METHODS

Long-term clinical studies using hepatitis A (HAV) or A/B vaccines (HAB) containing 720 or 1440 Enzyme-linked immunosorbent assay Units (EU) of hepatitis A virus antigen were identified. Duration of persistence of antibodies and possible protection was determined by descriptively comparing antibody geometric mean concentration (GMC) kinetics, as well as GMC (95% confidence interval) at 15 years post-vaccination across studies. Immunological mechanism studies describing hepatitis A vaccination were identified.

RESULTS

One study in children 12-15 years (2-dose HAB 720) and four in adults (2-dose HAV 1440 and 3-dose HAB 720) showed comparable GMC kinetics and per year rates of change up to 15 years. At 15 years, the GMC in children [414.7 mEU/ml (336.9; 510.5)] was in the same range as in adults [range 282.6 (217.6; 367.0) to 550.1 (416.0; 727.4)]. Based on these data, mathematical model predictions from adult studies (showing > 85% protected at 50 years) were deemed likely to also apply to children. Studies identified, both humoral and cell-mediated responses are induced following vaccination.

CONCLUSION

Based on comparable antibody data in adults and children up to 15 years, similar longer-term antibody persistence is expected in children with 2-dose inactivated hepatitis A 720 containing vaccine at least up to 50 years. Accordingly, improving routine childhood hepatitis A vaccination coverage could protect against more severe disease in adulthood. Fig. 1 Plain language summary TRIAL REGISTRATION: ClinicalTrials.gov identifiers, NCT00875485, NCT01000324, NCT01037114, NCT00289757, NCT00291876.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

This review is withdrawn because it is outdated. A new review is to be published by the end of 2019.

Increasing Burden of Hepatitis A in Adolescents and Adults and the Need for Long-Term Protection: A Review from the Indian Subcontinent

Hepatitis A, an acute inflammatory liver disease caused by hepatitis A virus (HAV) infection from close contact with infected people, is highly endemic in the Indian subcontinent. Due to poor sanitary conditions, most of the population is exposed to the virus in childhood. At this age, the disease is asymptomatic and provides life-long protection against the disease. Due to rapid socioeconomic development in some areas, however, pockets of the population are reaching adolescence/adulthood without prior exposure to the virus and are thus susceptible to infection. At these ages, infection carries a higher risk of symptomatic disease and complications including mortality. This review of epidemiology and burden of disease studies in the Indian subcontinent, published since 2005, shows increasing evidence of a shift from high to intermediate endemicity in high-income-typically urban-populations. The prevalence of anti-HAV antibodies (previously reported at > 90%) is lower now in adolescents and young adults (e.g., around 80% in Bangladesh and 55% in 5-15 years in India). As a result, HAV is responsible for more acute viral hepatitis predominantly in this age group (e.g., > 15 years: 3.4% in 1999 to 12.3% in 2003 or high socioeconomic status 13-20 years: 27% in 1999 to 62% in 2003), with a greater clinical and economic burden. Numerous outbreaks due to HAV have been reported [e.g., Sri Lanka (2009-2010): > 13,000 affected; Kashmir (2015-2017): 12 outbreaks; Kerala (2012-2016): 84 outbreaks] from water or food contamination. Due to current shifts in endemicity, a growing proportion of the population is no longer exposed in childhood. As the disease remains highly endemic, it also provides a source for more severe disease in susceptible people at an older age and for outbreaks. Well-tolerated and effective vaccines are available and help prevent disease burden and provide long-term protection. These should now be used more widely to protect more patients from the growing disease burden of hepatitis A. FUNDING: GlaxoSmithKline Biologicals SA. Plain language summary available for this article-please see Fig. 1 and the following link: https://doi.org/10.6084/m9.figshare.9963044.Fig. 1Plain Language Summary. Highlights the context of the article, the endemicity shift and the burden of hepatitis A in adolescents and adults and steps to be taken to address the impact of this disease.

Adherence to hepatitis A travel health guidelines: A cross-sectional seroprevalence study in Dutch travelling families - The Dutch travel Vaccination Study (DiVeST)

BACKGROUND

This Dutch travel Vaccination Study (DiVeST) aimed to study adherence or compliance to Dutch travel health guidelines in travelling families and to identify risk groups to provide better advice and protection for international travellers.

METHODS

Between 2016 and 2018, family members who travelled to Eastern Europe or outside Europe during the preceding year were recruited via Dutch secondary schools. The vaccination status of the travellers was assessed using questionnaires and vaccination records and hepatitis A virus antibody concentrations in dried blood spot (DBS) eluates. Subgroups of travellers with lower adherence to guidelines were identified.

RESULTS

Of the 246 travellers that participated in this study, 155 (63%) travelled to destinations for which the HAV vaccination was recommended. Of these 155 travellers, 56 (36%) said they visited a pre-travel clinic, and 64 of them (41%) showed a valid HAV vaccination in their vaccination records. Of the 145 travellers with available DBS eluates, anti-HAV antibodies were detected in 98 (68%) of them.

CONCLUSIONS

We found that adherence to travel health guidelines, in terms of HAV vaccination, was suboptimal. According to our results, specific attention should be paid to children, persons visiting friends and relatives and those who travel relatively short distances.

The Prevention of Infections in Older Adults: Vaccination

All living beings are at risk for experiencing infections; humans are no exception. The prestige and credibility of modern medicine is built in large part on achievements in preventing and treating infectious diseases. For most of human history, there was little that could be done to prevent and treat infections. Millions of humans, of all ages, have died from infections; and in some parts of the world, infection-related deaths remain common. Advances in preventing and treating infectious diseases include improved sanitization, sterilization, pasteurization, immunization, and antibiotics. Vaccination has played a major role in the prevention of lethal diseases, such as smallpox, diphtheria, cholera, and influenza. Because of developing or waning immune function, the young and the old are at particularly high risk of experiencing infections. Influenza and pneumonia remain common causes of death in older adults. Influenza, in particular, has the potential to result in premature mortality for all age groups, including those who are older and particularly those who live in congregate settings. Vaccination is important in promoting healthy aging. J Am Geriatr Soc 68:207-214, 2019.

Hepatitis A vaccine immunogenicity in patients using immunosuppressive drugs: A systematic review and meta-analysis

INTRODUCTION

Inactivated hepatitis A (HepA) vaccines are very immunogenic in healthy individuals; however, it remains unclear how different immunosuppressive regimens affect HepA vaccine immunogenicity. Our objective was to summarise the current evidence on immunogenicity of HepA vaccination in patients using immunosuppressive drugs.

METHODS

We systematically searched the literature for studies on immunogenicity of inactivated HepA vaccines in adults using immunosuppressive drugs. Studies reporting seroconversion rates (SCR) 4-8 weeks after 1 and 2 doses of HepA vaccine in organ transplant recipients and patients with chronic inflammatory conditions were included in a meta-analysis.

RESULTS

We included 17 studies, comprising 1,332 individuals. In healthy controls (2 studies), SCRs were 90-94% after the first dose and 100% after the second dose. In organ transplant recipients, SCRs ranged from 0 to 67% after the first dose of vaccine and 0-97% after the second dose. In patients with chronic inflammatory conditions, SCRs ranged from 6% to 100% after the first dose and from 48 to 100% after the second dose of vaccine. Patients using a TNF-alpha inhibitor versus conventional immune-modulators (e.g. methotrexate, azathioprine, corticosteroids) were more likely to seroconvert after the first dose of vaccine (OR12.1 [2.14-68.2]) but not after the second dose of vaccine (OR 0.78 [0.21-2.92]) in a meta-analysis.

CONCLUSION

Studies evaluating HepA vaccine immunogenicity in immunosuppressive agents are heterogeneous. Overall, there is an impaired immune response following HepA vaccination in patients using immunosuppressive drugs, especially after only one dose of vaccine and in organ transplant recipients. HepA vaccination should therefore be considered before immunosuppressive therapy. Future research should focus on alternative vaccination regimens and long-term immunogenicity.

PROSPERO ID

CRD42018102607.

Efficacy, immunogenicity and safety of vaccination in adult patients with autoimmune inflammatory rheumatic diseases: a systematic literature review for the 2019 update of EULAR recommendations

Aim

To present a systematic literature review (SLR) on efficacy, immunogenicity and safety of vaccination in adult patients with autoimmune inflammatory rheumatic diseases (AIIRD), aiming to provide a basis for updating the EULAR evidence-based recommendations.

Methods

An SLR was performed according to the standard operating procedures for EULAR-endorsed recommendations. Outcome was determined by efficacy, immunogenicity and safety of vaccination in adult patients with AIIRD, including those receiving immunomodulating therapy. Furthermore, a search was performed on the effect of vaccinating household members of patients with AIIRD on the occurrence of vaccine-preventable infections in patients and their household members (including newborns). The literature search was performed using Medline, Embase and the Cochrane Library (October 2009 to August 2018).

Results

While most investigated vaccines were efficacious and/or immunogenic in patients with AIIRD, some were less efficacious than in healthy control subjects, and/or in patients receiving immunosuppressive agents. Adverse events of vaccination were generally mild and the rates were comparable to those in healthy persons. Vaccination did not seem to lead to an increase in activity of the underlying AIIRD, but insufficient power of most studies precluded arriving at definite conclusions. The number of studies investigating clinical efficacy of vaccination is still limited. No studies on the effect of vaccinating household members of patients with AIIRD were retrieved.

Conclusion

Evidence on efficacy, immunogenicity and safety of vaccination in patients with AIIRD was systematically reviewed to provide a basis for updated recommendations.

A review of immunogenicity and tolerability of live attenuated Hepatitis A vaccine in children

Changing epidemiology of Hepatitis A virus (HAV) has led to an increased susceptibility of adolescents and adults to the infection. Vaccination can remarkably reduce the incidence and associated morbidity of HAV infection. This review is focused on the safety and efficacy of H2 strain derived live attenuated Hepatitis A vaccine. We found the vaccine to be highly immunogenic with minimal or negligible safety issues. Moreover, a single dose of live attenuated vaccine persists a long term immune response and can be a preferred option for developing countries. In 2014, Indian Academy of Paediatrics (IAP) also updated their recommendations for H2 vaccine as a single dose as against the previous 2 dose schedule. A focused approach to include the vaccine in national immunization program should be explored.

A retrospective pooled analysis assessing the effect of age on the immunogenicity of Havrix™ in healthy adults

Over recent decades, the global incidence of hepatitis A virus infection has been reduced by improvements in sanitation infrastructure and through immunization programs. The immunogenicity and field efficacy of the inactivated hepatitis A vaccine (Havrix™, GSK, Belgium) has been demonstrated in clinical trials, population-impact studies as well as in several outbreak settings. However, immunological data in older populations are limited, with only few studies assessing the immune response of this vaccine in adults aged ≥40 years. This retrospective pooled analysis of 4 2-dose primary vaccination studies compared the immunogenicity and safety of the inactivated hepatitis A vaccine in adults aged ≥40 years with subjects aged 20–30 years (control group; N = 80 in each group). Fifteen days after the first vaccine dose, 79.7% (95% CI: 68.8–88.2) and 92.3% (95% CI: 84.0–97.1) of subjects were seropositive in the ≥40 years and control groups, respectively; 97.5% (95% CI: 91.2–99.7) and 97.4% (95% CI: 91.0–99.7), respectively, were seropositive one month after the first dose. All subjects in both groups (95% CIs: 95.4–100 and 95.3–100, respectively) were seropositive one month after the second dose. Safety profiles were similar in both groups. In conclusion, the inactivated hepatitis A vaccine induced similar immune responses in adults aged ≥40 and 20–30 years one month after the first and second dose whereas younger subjects may demonstrate a higher seroconversion rate 15 days after the first dose.

Dietary plant stanol ester consumption improves immune function in asthma patients: results of a randomized, double-blind clinical trial

BACKGROUND

In vitro and ex vivo studies have suggested that plant sterols and stanols can shift the T helper (Th) 1/Th2 balance toward a Th1-type immune response, which may be beneficial in Th2-dominant conditions such as asthma and allergies.

OBJECTIVE

We evaluated in vivo whether plant stanol esters affect the immune response in asthma patients.

DESIGN

Fifty-eight asthma patients participated in a randomized, double-blind, placebo-controlled intervention study. All subjects started with a 2-wk run-in period in which they consumed 150 mL control soy-based yogurt without added plant stanol esters/d. Next, an 8-wk experimental period was started in which one-half of the participants received plant stanol enriched soy-based yogurts (4.0 g plant stanols/d), whereas the other one-half of subjects continued the consumption of control yogurts. After 4 wk of daily plant stanol consumption, all participants were vaccinated against hepatitis A virus (HAV), and the increase of antibody titres was monitored weekly until 4 wk after vaccination.

RESULTS

Asthma patients in the plant stanol ester group showed higher antibody titres against HAV 3 and 4 wk after vaccination [19% (P = 0.037) and 22% (P = 0.030), respectively]. Also, substantial reductions in plasma total immunoglobulin E, interleukin (IL)-1β, and tumor necrosis factor-α were shown in the plant stanol ester group. The increase in serum plant stanol concentrations was correlated significantly with the decrease in IL-13 concentrations and the Th1 switch in the Th1/Th2 balance. However, no absolute differences in cytokine production between the plant stanol ester group and the control group were shown.

CONCLUSION

To the best of our knowledge, we are among the first authors to show that plant stanol ester consumption improves the immune function in vivo in asthma patients. This trial was registered at clinicaltrials.gov as NCT01715675.

Decreasing immunity to hepatitis A virus infection among US adults: Findings from the National Health and Nutrition Examination Survey (NHANES), 1999-2012

BACKGROUND

The clinical course of hepatitis A virus (HAV) infection is more severe with increased age. In the United States, surveillance data reported to CDC since 2011 indicate increases in both the absolute number of cases and the mean age of cases. Total antibody to HAV (anti-HAV) is a marker of immunity.

METHODS

We analyzed National Health and Nutrition Examination Survey (NHANES) data for anti-HAV from respondents aged ≥ 2 years collected from 2007 to 2012 and compared with data collected 10 years earlier (1999-2006). For US-born adults aged ≥ 20 years, we estimated age-adjusted anti-HAV prevalence by demographic and other characteristics, evaluated factors associated with anti-HAV positivity and examined anti-HAV prevalence by decade of birth.

RESULTS

The prevalence of anti-HAV among adults aged ≥ 20 years was 24.2% (95% CI 22.5-25.9) during 2007-2012, a significant decline from 29.5% (95% CI 28.0-31.1) during 1999-2006. Prevalence of anti-HAV was consistently lower in 2007-2012 compared to 1999-2006 by all characteristics examined. In 2007-2012, the lowest age-specific prevalence was among adults aged 30-49 years (16.1-17.6%). Factors significantly associated with anti-HAV positivity among adults were older age, Mexican American ethnicity, living below poverty, less education, and not having insurance. By decade of birth, the prevalence of anti-HAV was slightly lower in 2009-2012 than in 1999-2002, except among persons born from 1980 to 1989.

CONCLUSIONS

NHANES data document very low prevalence of hepatitis A immunity among U.S. adults aged 30-49 years; waning of anti-HAV over time may be minimal. Improving vaccination coverage among susceptible adults should be considered.

Hepatitis A vaccine for immunosuppressed patients with rheumatoid arthritis: a prospective, open-label, multi-centre study

BACKGROUND

Hepatitis A vaccine is the most frequently used travel vaccine, yet data are scarce about its ability to induce protection in patients with concurrent immunosuppressive treatment. We assessed the immunogenicity of this vaccine in rheumatoid arthritis (RA) patients treated with tumour necrosis factor-inhibitors (TNFi) and/or methotrexate (MTX).

METHODS

Hepatitis A vaccine was administered to non-immune RA patients at 0 and 6 months. Hepatitis A virus (HAV) antibodies were assessed at 0, 1, 6, 7, 12, and 24 months with a quantitative Chemiluminescent Microparticle Immuno Assay (CMIA) for HAV-IgG. Samples from month 1, 6, and 7 were, in addition, analysed with a microparticle EIA (MEIA) for anti-HAV IgM + IgG.

RESULTS

The final study population consisted of 53 patients treated with TNFi (n = 15), TNFi + MTX (n = 21) or MTX (n = 17). One and six months after the first dose, 10% and 33% of the patients had attained seroprotection. One and six months after the second dose 83% and 72% were seroprotected. At month 24, 86% of the vaccinees showed protective levels.

CONCLUSIONS

Two doses of hepatitis A vaccine at a 6-month interval provided protection for most immunosuppressed RA patients. A single dose does not seem to afford sufficient protection to this group of patients.

Immunogenecity of hepatitis A and B vaccination in pediatric patients with inflammatory bowel disease

OBJECTIVES

Aim of the study was to evaluate the response to hepatitis A and B vaccination in pediatric patients with inflammatory bowel disease (IBD).

METHODS

A total of 47 patients with IBD (25 ulcerative colitis, 14 Crohn's disease, and 8 indeterminate colitis) ages 3 to 17 years were compared with 50 healthy age- and sex-matched controls. Screening for hepatitis A and B serology was carried out before vaccination. Susceptible cases received 20 mg of recombinant DNA vaccine for hepatitis B (0, 1, and 6 months)and 720 milliELISA units of inactivated hepatitis A virus vaccine (HAV) (0 and 6 months). Postvaccination serologic evaluation was performed 1 month after the last dose of primary vaccination, 1 month after the booster dose, and once every year during follow-up.

RESULTS

A total of 23 patients and 35 controls received HAV and protective anti-HAV antibodies were developed in all of the patients and controls (P =1.00). Forty-seven patients and 50 controls received hepatitis B vaccine and 70.2% of the patients versus 90% of the controls achieved seroprotection(anti-HBs titers 10 mIU/mL) 1 month after primary vaccination (95% confidence interval 0.71–0.87, P = 0.02). The overall seroprotection rates were 96% in controls and 85.1% in patients after the whole hepatitis B vaccination series (95% confidence interval 0.83–0.95, P = 0.08). No significant reduction was observed in antibody response among patients and controls during the follow-up period.

CONCLUSIONS

The rate of seroconversion to the hepatitis B vaccine was lower in pediatric patients with IBD than in healthy controls and hepatitis A vaccine was highly immunogenic among patients with IBD.

Response to hepatitis A and B vaccination in pediatric patients with celiac disease

OBJECTIVES

The aim of the study was to evaluate the response to hepatitis A and B vaccinations in pediatric patients with celiac disease (CD).

METHODS

Thirty patients with CD ages 1 to 15 years were compared with 50 healthy age-, sex-, and body mass index-matched controls. Screening for hepatitis A and B serology was carried out before vaccination. Susceptible cases received 20 μg of recombinant DNA vaccine for hepatitis B (0,1, and 6 months) and 720 milliELISA units of inactivated hepatitis A virus (HAV) vaccine (0 and 6 months). Postvaccination serologic evaluation was performed 1 month after the last dose of primary vaccination, 1 month after the booster dose, and once every year during follow-up.

RESULTS

Sixteen patients and 35 controls received hepatitis A vaccine; protective anti-HAV antibodies were developed in 12 (75%) of the patients and all of the controls (75% vs 100%, respectively; 95% confidence interval [CI] 0.47-0.92, P=0.007). Thirty patients and 50 controls received hepatitis B vaccine, and 70% of the patients vs 90% of the controls achieved seroprotection (anti-HBs titers ≥10 mIU/mL) 1 month after primary vaccination (95% CI 0.74-0.90, P=0.03). Four patients were unresponsive to both of the vaccines. The overall seroprotection rates were 96% in controls and 80% in patients after the whole hepatitis B vaccination series (95% CI 0.04-0.18, P=0.04). No significant reduction was observed in antibody response among patients and controls during follow-up period.

CONCLUSIONS

The rate of seroconversion to the hepatitis B virus- and HAV vaccine is lower in patients with CD than in healthy controls.

Declining incidence of hepatitis A in Amsterdam (The Netherlands), 1996-2011: second generation migrants still an important risk group for virus importation

BACKGROUND

The Netherlands is a very low endemic country for hepatitis A virus infections (HAV, notification rate of <1/100,000). Historically in Amsterdam, a large proportion of infections are imported from Turkey and Morocco in children returning from summer holiday. Annually since 1998, the public health service of Amsterdam has targeted these children for HAV vaccination before the summer. As the population of non-western immigrants and their descendents increases, we describe recent trends in HAV in ethnic groups in Amsterdam (1996-2011), identifying current risk groups and recommending targeted prevention through vaccination.

METHODS

We studied all cases of (non-homosexually acquired) HAV infection notified in the Amsterdam region (1996-2011, n=819) by ethnic group and generation (first/second generation migrants: FGM and SGM respectively). Incidence rates were estimated as the average number of cases per 100,000/year. Using Poisson regression, we calculated incidence rate ratios (IRR) by ethnic group and generation adjusted for age and calendar year, and modeled seasonal variation using a smoothed time series.

RESULTS

Incidence of HAV in Amsterdam dropped from 24.8/100,000 population in 1996 (178 cases) to 1.0/100,000 in 2011 (8 cases). Since 2005, 56% of cases are imported, the majority (62%) in second generation migrant (SGM) children of Moroccan, or other non-western ethnic backgrounds. The adjusted IRR in SGM relative to the ethnic Dutch population was 3.7 (95% CI: 2.3-6.1) in Moroccan SGM, 4.3 (95%CI: 2.6-7.2) in SGM of other non-western backgrounds and 1.9 (95%CI: 0.8-4.1) in Turkish SGM.

CONCLUSION

Though incidence of HAV in Amsterdam has declined substantially since 1996, it is still higher in SGM children of Moroccan & other non-western ethnic backgrounds. In line with WHO recommendations of June 2012, introduction of single-dose HAV vaccination, targeted at SGM children from HAV endemic countries, could be considered within the routine childhood vaccination schedule.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

BACKGROUND

In many parts of the world, hepatitis A infection represents a significant cause of morbidity and socio-economic loss. Whilst hepatitis A vaccines have the potential to prevent disease, the degree of protection afforded against clinical outcomes and within different populations remains uncertain. There are two types of hepatitis A virus (HAV) vaccine, inactivated and live attenuated. It is important to determine the efficacy and safety for both vaccine types.

OBJECTIVES

To determine the clinical protective efficacy, sero-protective efficacy, and safety and harms of hepatitis A vaccination in persons not previously exposed to hepatitis A.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and China National Knowledge Infrastructure (CNKI) up to November 2011.

SELECTION CRITERIA

Randomised clinical trials comparing HAV vaccine with placebo, no intervention, or appropriate control vaccines in participants of all ages.

DATA COLLECTION AND ANALYSIS

Data extraction and risk of bias assessment were undertaken by two authors and verified by a third author. Where required, authors contacted investigators to obtain missing data. The primary outcome was the occurrence of clinically apparent hepatitis A (infectious hepatitis). The secondary outcomes were lack of sero-protective anti-HAV immunoglobulin G (IgG), and number and types of adverse events. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Dichotomous outcomes were reported as risk ratio (RR) with 95% confidence interval (CI), using intention-to-treat analysis. We conducted assessment of risk of bias to evaluate the risk of systematic errors (bias) and trial sequential analyses to estimate the risk of random errors (the play of chance).

MAIN RESULTS

We included a total of 11 clinical studies, of which only three were considered to have low risk of bias; two were quasi-randomised studies in which we only addressed harms. Nine randomised trials with 732,380 participants addressed the primary outcome of clinically confirmed hepatitis A. Of these, four trials assessed the inactivated hepatitis A vaccine (41,690 participants) and five trials assessed the live attenuated hepatitis A vaccine (690,690 participants). In the three randomised trials with low risk of bias (all assessing inactivated vaccine), clinically apparent hepatitis A occurred in 9/20,684 (0.04%) versus 92/20,746 (0.44%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.03 to 0.30). In all nine randomised trials, clinically apparent hepatitis A occurred in 31/375,726 (0.01%) versus 505/356,654 (0.18%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.05 to 0.17). These results were supported by trial sequential analyses. Subgroup analyses confirmed the clinical effectiveness of both inactivated hepatitis A vaccines (RR 0.09, 95% CI 0.03 to 0.30) and live attenuated hepatitis A vaccines (RR 0.07, 95% CI 0.03 to 0.17) on clinically confirmed hepatitis A. Inactivated hepatitis A vaccines had a significant effect on reducing the lack of sero-protection (less than 20 mIU/L) (RR 0.01, 95% CI 0.00 to 0.03). No trial reported on a sero-protective threshold less than 10 mIU/L. The risk of both non-serious local and systemic adverse events was comparable to placebo for the inactivated HAV vaccines. There were insufficient data to draw conclusions on adverse events for the live attenuated HAV vaccine.

AUTHORS' CONCLUSIONS

Hepatitis A vaccines are effective for pre-exposure prophylaxis of hepatitis A in susceptible individuals. This review demonstrated significant protection for at least two years with the inactivated HAV vaccine and at least five years with the live attenuated HAV vaccine. There was evidence to support the safety of the inactivated hepatitis A vaccine. More high quality evidence is required to determine the safety of live attenuated vaccines.

The use of dried blood spots for assessing antibody response to hepatitis A virus after natural infection and vaccination

During recent years, vaccination against hepatitis A has been implemented in several countries. It is expected that the increase in mass vaccination against hepatitis A will eventually result in a decreased prevalence of anti-HAV antibodies in the general population. For this reason, a suitable clinical sample for diagnosis of hepatitis A must be sufficiently sensitive to enable detection of lower antibodies titers. In this study, the feasibility of using dried blood spots (DBS) was assessed for the detection of anti-HAV antibodies after a natural infection and vaccination. Seventy-four DBS and paired plasma samples were obtained from a group of college students for a cross-sectional hepatitis A seroepidemiological study. Forty-six students seronegative for anti-HAV were selected randomly and immunized with an inactivated hepatitis A vaccine using an 0-6 month schedule. Seroconversion was monitored in paired plasma and DBS samples 6 months after the first dose followed by a period of 8 and 24 months after the second dose. A strong correlation between OD/CO rates of paired plasma and DBS samples for the detection of anti-HAV was observed. The sensitivity and specificity of the DBS compared with plasma for the detection of anti-HAV antibodies after natural infection was 100%. The sensitivity of DBS in samples collected 24 months after the second dose of hepatitis A vaccine was 95.4%. The results showed that DBS samples can be used for the detection of anti-HAV antibodies both after natural infection or vaccination.

Correlates of protection induced by vaccination

This paper attempts to summarize current knowledge about immune responses to vaccines that correlate with protection. Although the immune system is redundant, almost all current vaccines work through antibodies in serum or on mucosa that block infection or bacteremia/viremia and thus provide a correlate of protection. The functional characteristics of antibodies, as well as quantity, are important. Antibody may be highly correlated with protection or synergistic with other functions. Immune memory is a critical correlate: effector memory for short-incubation diseases and central memory for long-incubation diseases. Cellular immunity acts to kill or suppress intracellular pathogens and may also synergize with antibody. For some vaccines, we have no true correlates, but only useful surrogates, for an unknown protective response.

Virologic and immunologic correlates with the magnitude of antibody responses to the hepatitis A vaccine in HIV-infected children on highly active antiretroviral treatment

BACKGROUND

HIV-infected individuals mount poor antibody responses to vaccines. We sought to identify the immunologic and virologic factors associated with a robust response to hepatitis A virus (HAV) vaccine in children on highly active antiretroviral treatment.

METHODS

One hundred fifty-two pediatric highly active antiretroviral treatment recipients immunized against HAV at weeks 0 and 24 had anti-HAV antibodies, CD4+, CD8+, and CD19+ cell percent assessed at weeks 0 and 32. Subgroups had HIV viremia, B- and T-cell subpopulations, and cell-mediated immunity (CMI) to HAV and other stimulants measured.

RESULTS

Anti-HAV antibodies after complete vaccination correlated positively with CD4+ percent and CD19+ percent and negatively with viremia and CD8+ percent at baseline, but not at 32 weeks. There were no significant correlations between anti-HAV antibodies and B- or T-cell-naïve, memory, or activated subpopulations or non-HAV CMI. Compared with children who remained HAV-CMI-negative, those who mounted HAV-CMI in response to vaccination had higher anti-HAV antibody titers and CD19+ CD21+ CD27+ memory B cell percent at 32 weeks, but no other differences.

CONCLUSIONS

In HIV-infected children on highly active antiretroviral treatment, control of viral replication and conserved or reconstituted CD19+ and CD4+ cell numbers and function determine a robust antibody response to anti-HAV primary immunization. Our data support a bidirectional B- and T-cell cooperation in the response to the HAV vaccine.

Correlation between humoral and cellular immune responses and the expression of the hepatitis A receptor HAVcr-1 on T cells after hepatitis A re-vaccination in high and low-responder vaccinees

INTRODUCTION

We recently published a study on the persistence of seroprotection 10 years after primary hepatitis A vaccination in an unselected study population of 1014 vaccinees. The majority of these vaccinees still exhibited sufficient protective antibody levels, while 2% displayed antibody concentrations below detection level. In order to investigate whether the low antibody levels were due to decline after primary vaccination or due to an intrinsic inability to sufficiently respond to hepatitis A antigen, we sought to recruit these low/no responder vaccinees to characterize their immune responses in more detail after booster vaccination in comparison to high responder vaccinees.

MATERIALS AND METHODS

Prior to and one week after booster vaccination with a hepatitis A vaccine, antibody levels, cytokine levels (IL-2, IFN-gamma and IL-10) and CD surface marker expression on peripheral blood mononuclear cells were determined in a study population comprised of 52 individuals. Additionally, the hepatitis A HAV cellular receptor 1 (HAVcr-1) TIM-1, being also expressed on CD4+ T cells and associated with immunomodulatory properties, was measured by RT-PCR before and after hepatitis A booster.

RESULTS

Our data indicate that there is indeed a small group of hepatitis A vaccinees that can be classified as low/no responders as their antibody levels remain below the seroprotection level of 20mIU/ml after booster vaccination. We further describe a good correlation between antibody concentrations and cellular responses, showing that low antibody production is associated with low antigen specific cytokine levels (IL-2, IFN-gamma, IL-10) and vice versa. While there was no significant difference in the expression of the most common surface markers on T and B cells before and after booster vaccination in low and high responder vaccinees, the expression of HAVcr-1 on CD4 T cells correlated significantly with the antibody responses and cytokine levels, suggesting this receptor as cellular prediction marker of immune responsiveness to hepatitis A.

CONCLUSION

Whether hepatitis A low/non-responders deserve particular attention as a risk group or might display certain resistance to hepatitis A infection due to a lack of the hepatitis A receptor needs further investigations. At this stage we suggest that persons at high exposure risk should be carefully observed.

Functional signatures of protective antiviral T-cell immunity in human virus infections

The most common human viruses have different abilities to establish persistent chronic infection. Virus-specific T-cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus-specific CD4+ and CD8+ T-cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T-cell responses against different viruses. The heterogeneity of the T-cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T-cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T-cell response within the same virus infection. Furthermore, the functional characterization of virus-specific CD4+ and CD8+ T-cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin-2 and interferon-gamma (IFN-gamma) secretion and proliferation, and not monofunctional, i.e. IFN-gamma secretion, CD4+ and CD8+ T-cell responses represent correlates of protective antiviral immunity in chronic virus infections.

Cell-mediated immunity and the challenges for vaccine development

One of the hallmarks of successful vaccination is the induction of strong and persistent memory T cell responses, a process that involves striking changes in the number and functional properties of T cells. Many questions pertaining to this complex, multifaceted process remain unanswered. Some of the key issues and challenges to optimize memory T cell responses and foster vaccine development include the optimization of effector T cell burst sizes, the use of adjuvants, cytokines and co-stimulatory molecules, epitope enhancement and the standardization of techniques to detect specific T cells. Age also has an impact on vaccine design because of the physiological changes in cell-mediated immunity that occur throughout life.

Immunogenicity of a chimeric hepatitis A virus (HAV) carrying the HIV gp41 epitope 2F5

Its stable particle structure combined with its high immunogenicity makes the hepatitis A virus (HAV) a perfect carrier to expose foreign epitopes to the host immune system. In an earlier report [Beneduce, F., Kusov, Y., Klinger, M., Gauss-Müller, V., Morace, G., 2002. Chimeric hepatitis A virus particles presenting a foreign epitope (HIV gp41) at their surface. Antiviral Res. 55, 369-377] chimeric virus-like particles (HAV-gp41) were described that carried at their surface the dominant gp41 epitope 2F5 (2F5e) of the human immunodeficiency virus HIV-1. Extending this work, we now report that chimeric virus HAV-gp41 replicates in HAV-susceptible cells as well as in non-human primates. Infected marmosets developed both an anti-HAV and anti-2F5 epitope immune response. Furthermore, an HIV-neutralizing antibody response was elicited in guinea pigs immunized with HAV-gp41 chimeric particles. The results demonstrate that the replication-competent chimeric HAV-gp41 can serve as either a live or a subunit vaccine for eliciting of antibodies directed against a foreign antigenic epitope.