Clinical and virological features of acute hepatitis A during an ongoing outbreak among men who have sex with men in the North of France

Evolution and Impact of Hepatitis A Epidemiology in Europe-Systematic Literature Review of the Last 20 Years

While globally hepatitis A (hepA) infections occur in 150 million people annually, European high-income countries now have a low endemicity. However, this results in a more susceptible adult population which is prone to severe illness. To determine current epidemiological characteristics, we performed a systematic literature review to assess the severity of hepA disease in the past two decades in 11 European countries (i.e., Denmark, France, Germany, Greece, Hungary, Italy, the Netherlands, Spain, Sweden, Switzerland and the United Kingdom). Literature search was performed using PubMed and Embase between 1 January 2001 and 14 April 2021. Search terms included the disease (hepA), the 11 selected countries, the term 'outbreaks' and its synonyms, outcomes and terms for hepA virus circulation. In total, 43 records reported data on hepA disease outcomes. Hospitalisation rates varied between the countries, with annual rates exceeding 50% at least once in seven countries. The lowest hospitalisation rates were reported for the Netherlands (≤ 32%) and the highest for Greece (≥ 81%). Liver failure, haemorrhagic and other complications were rarely reported, and case fatality rates were low (0.03%-0.26%). Our findings are consistent with the trends observed globally. This systematic literature review highlights the need to increase awareness of hepA risks and to strengthen prevention strategies. Continuous monitoring of epidemiological data is crucial to assess which populations would most benefit from prevention, mainly with respect to future vaccination recommendations.

Delays in Hepatitis A vaccination in people with HIV in Houston, Texas between 2010 and 2018

Background

Studies have demonstrated low hepatitis A virus (HAV) vaccination rates among persons with HIV (PWH).

Methods

We conducted a retrospective study of persons entering HIV care at two clinics in Houston, Texas between 2010 and 2018. We defined those eligible for HAV vaccination as those who had no history of HAV vaccination and had a negative anti-HAV IgG at entry to care. Kaplan-Meier curves summarized time to receipt of HAV vaccines. The proportions of patients who received 1 and 2 HAV vaccines at 6, 12, and 24 months were estimated. Cox proportional hazards regression evaluated associations between patient characteristics and vaccination. Significant factors were included in a multivariable Cox proportional hazards model.

Results

Of 6,515 patients, 1372 were eligible for HAV vaccination. Of eligible patients, 29.2 % received 1 HAV vaccination at 6 months, 37.1 % at 12 months, and 47.8 % at 24 months. At 6 months, 10 % received 2 HAV vaccinations, 21.1 % at 12 months, and 33.4 % at 24 months. In multivariable analysis, men who have sex with men (adjusted HR 1.35, 95 % CI 1.06, 1.73) or those who had CD4 count ≥ 200 cells/µl (adjusted HR 2.52, 95 % CI 1.89, 3.37) had their second vaccination sooner than those who were not men who have sex with men or who had CD4 counts < 200 cells/µl, respectively. Patients > 50 years of age had their second vaccination sooner than those aged 30-50 years (adjusted HR 1.47, 95 % CI 1.08, 1.99). Those with active substance history had a longer time to second vaccination compared to those with no substance use history (adjusted HR 0.57, 95 % CI 0.40, 0.82).

Conclusions

HAV vaccination rates were low and highlight the need for effective solutions to address HAV immunization gaps in PWH, especially among young patients, those with active substance use disorders, and those with significant immunocompromise.

Immunogenicity and Efficacy of Vaccination in People Living with Human Immunodeficiency Virus

People living with HIV (PLWH) remain at high risk of mortality and morbidity from vaccine-preventable diseases, even though antiretroviral therapy (ART) has restored life expectancy and general well-being. When, which, and how many doses of vaccine should be administered over the lifetime of PLWH are questions that have become clinically relevant. Immune responses to most vaccines are known to be impaired in PLWH. Effective control of viremia with ART and restored CD4+ T-cell count are correlated with an improvement in responsiveness to routine vaccines. However, the presence of immune alterations, comorbidities and co-infections may alter it. In this article, we provide a comprehensive review of the literature on immune responses to different vaccines in the setting of HIV infection, emphasizing the potential effect of HIV-related factors and presence of comorbidities in modulating such responses. A better understanding of these issues will help guide vaccination and prevention strategies for PLWH.

Hepatitis A occurrence and outbreaks in Europe over the past two decades: A systematic review

Hepatitis A (HA) is a vaccine-preventable liver disease with >170 million new cases occurring yearly. In recent outbreaks in the USA, hospitalization and case-fatality ratios were >60% and ~1%, respectively. In Europe, endemicity persists and outbreaks continue to occur. We performed a systematic literature review to understand the changes in HA occurrence in Europe over the past two decades. PubMed and Embase were systematically searched for peer-reviewed articles published between 1 January 2001 and 14 April 2021 using terms covering HA, 11 selected European countries, outbreaks, outcomes and HA virus circulation. Here, we focus on HA occurrence and outbreaks in the five countries with the largest population and the most comprehensive vaccination recommendations: France, Germany, Italy, Spain and the UK; 118 reports included data for these five European countries. Notification rates (≤9.7/100,000 population) and percentages of men among cases (≤83.0%) peaked in 2017. The number of person-to-person-transmitted cases and outbreaks decreased in children but increased in other risk groups, such as men who have sex with men (MSM). Sexually transmitted outbreaks in MSM clustered around 2017. Travel-related outbreaks were few; the proportion of travel-related cases decreased during the past two decades, while the number of domestic cases increased. Despite the existing risk-based vaccination recommendations, HA transmission shifted in proportions from travelers and children to other risk groups, such as MSM and older age groups. Because a substantial proportion of the European population is susceptible to HA, adherence to existing recommendations should be monitored more closely, and enhanced vaccination strategies should be considered.

Hepatitis A: Viral Structure, Classification, Life Cycle, Clinical Symptoms, Diagnosis Error, and Vaccination

Hepatitis A virus (HAV) is one of the well-known viruses that cause hepatitis all around the globe. Although this illness has decreased in developed countries due to extensive immunization, numerous developing and under-developed countries are struggling with this virus. HAV infection can be spread by oral-fecal contact, and there are frequent epidemics through nutrition. Improvements in socioeconomic and sanitary circumstances have caused a shift in the disease's prevalence worldwide. Younger children are usually asymptomatic, but as they become older, the infection symptoms begin to appear. Symptoms range from slight inflammation and jaundice to acute liver failure in older individuals. While an acute infection may be self-limiting, unrecognized persistent infections, and the misapplication of therapeutic methods based on clinical guidelines are linked to a higher incidence of cirrhosis, hepatocellular carcinoma, and mortality. Fortunately, most patients recover within two months of infection, though 10-15% of patients will relapse within the first six months. A virus seldom leads to persistent infection or liver damage. The mainstay of therapy is based on supportive care. All children from 12-23 months, as well as some susceptible populations, should receive routine vaccinations, according to the Centers for Disease Control and Prevention and the American Academy of Pediatrics. Laboratory diagnosis of HAV is based on antigen detection, checking liver enzyme levels, and antibody screening. Furthermore, polymerase chain reaction (PCR) technology has identified HAV in suspected nutrition sources; therefore, this technique is used for preventative measures and food-related laws.

Hepatitis A Outbreak in Men Who Have Sex with Men Using Pre-Exposure Prophylaxis and People Living with HIV in Croatia, January to October 2022

The hepatitis A virus (HAV) is a highly hepatotropic virus transmitted mainly via the fecal-oral route. The purpose of this study is to describe a prolonged HAV outbreak in HIV-infected men who have sex with men (MSM) and pre-exposure prophylaxis (PrEP) users in Croatia in 2022. Croatia has a centralized system of HIV care and the PrEP service is only available at the University Hospital for Infectious Diseases (UHID), Zagreb. We reviewed all MSM living with HIV and MSM PrEP users at UHID and identified those diagnosed with HAV between January and October 2022. During this period, a total of 1036 MSM living with HIV and 361 PrEP users were followed, and 45 (4.4%) and 32 (8.9%) were diagnosed with HAV, respectively. Most cases were diagnosed in mid-February. A total of 70.1% (726/1036) MSM living with HIV and 82.3% (297/361) PrEP users were susceptible to HAV. Sequencing information was available for 34 persons; in all cases the HAV subtype IA was found. Our findings indicate that both MSM living with HIV and HIV-uninfected PrEP users are vulnerable to HAV infection and might be a potential source for a more widespread HAV epidemic.

Assessing countermeasures during a hepatitis A virus outbreak among men who have sex with men

Background

A hepatitis A epidemic occurred among men who have sex with men (MSM) in Japan in 2017–2018. In this study, we employ a parsimonious mathematical model to epidemiologically investigate the dynamics of infection, aiming to evaluate the effectiveness of campaign-based interventions among MSM to raise awareness of the situation.

Methods

A mathematical model describing a mixture of human-to-human transmission and environmental transmission was fitted to surveillance data. Taking seasonally varying environmental transmission into account, we estimated the reproduction number of hepatitis A virus during the course of epidemic, and, especially, the abrupt decline in this reproduction number following campaign-based interventions.

Results

The reproduction number prior to the countermeasures ranged from 2.6 to 3.1 and then began to decrease following campaign-based interventions. After the first countermeasure, the reproduction number decreased, but the epidemic remained supercritical (i.e., R_t > 1). The value of R_t dropped well below one following the second countermeasure, which used web articles to widely disseminate information about the epidemic risk.

Conclusions

Although the effective reproduction number, R_t, changes because of both intrinsic and extrinsic factors, the timing of the examined countermeasures against hepatitis A in the MSM population was consistent with the abrupt declines observed in R_t. Even without vaccination, the epidemic was brought under control, and risky behaviors may have been changed by the increase in situation awareness reached through web articles.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12976-021-00150-1.

Outbreak of hepatitis A in a post-vaccination era: High rate of co-infection with sexually transmitted diseases

INTRODUCTION AND OBJECTIVES

After hepatitis A (HAV) mandatory immunization in 2005 in Argentina, the incidence of HAV declined drastically. However, several new autochthonous cases of HAV have been reported since 2017. We aimed to evaluate the clinical and epidemiological characteristics and possible transmission routes of affected patients.

PATIENTS OR MATERIALS AND METHODS

We performed a cross-sectional study of patients residing in Argentina with acute hepatitis A between 30.06.2017 and 31.12.2018.

RESULTS

66 cases of HAV were registered. Fifty-six patients (86%) were males, with a mean age of 34 ± 12 years old. The most likely routes of transmission were sexual intercourse of men with men, reported by 31 patients. Additionally, 23% and 26% of patients tested positive for HIV and syphilis, respectively. In total, 35% of patients required hospitalization. When assessing outcomes, 79% had a mild presentation and 21% had a severe/fulminant presentation: one patient underwent liver transplantation, and one patient died.

CONCLUSIONS

Our study describes that during the study period, HAV infection affected predominantly young adults, particularly men who have sex with men. An elevated proportion of them was diagnosed with a concomitant sexually transmitted disease, and several patients had a severe presentation of the disease.

Hepatitis A: Epidemiology, High-Risk Groups, Prevention and Research on Antiviral Treatment

The hepatitis A virus (HAV) is a leading cause of acute viral hepatitis worldwide. It is transmitted mainly by direct contact with patients who have been infected or by ingesting contaminated water or food. The virus is endemic in low-income countries where sanitary and sociodemographic conditions are poor. Paradoxically, improving sanitary conditions in these countries, which reduces the incidence of HAV infections, can lead to more severe disease in susceptible adults. The populations of developed countries are highly susceptible to HAV, and large outbreaks can occur when the virus is spread by globalization and by increased travel and movement of foodstuffs. Most of these outbreaks occur among high-risk groups: travellers, men who have sex with men, people who use substances, and people facing homelessness. Hepatitis A infections can be prevented by vaccination; safe and effective vaccines have been available for decades. Several countries have successfully introduced universal mass vaccination for children, but high-risk groups in high-income countries remain insufficiently protected. The development of HAV antivirals may be important to control HAV outbreaks in developed countries where a universal vaccination programme is not recommended.

Acute Hepatitis A Outbreak Among Men Who Have Sex With Men in Krakow, Poland; February 2017-February 2018

Since February 2017 in Poland, an increasing number of acute hepatitis A (AHA) cases have been reported; a noteworthy increase to 3,072 cases of AHA in 2017 compared to 35 cases in 2016 was reported by the National Institute of Public Health (NIPH). The aim of this study was to evaluate the demographic features, clinical manifestations, laboratory results, and sexually transmitted coinfections. All cases of AHA diagnosed between February 2017 and February 2018 at the University Hospital in Krakow were analyzed. A total of 119 cases of hepatitis A virus (HAV) were reported; 105 (88%) were males and 14 (12%) were females, with a mean age 31 years (range 19–62). In 84 patients (71%), the HAV was transmitted by oral–anal sexual contact between men. Six women were infected by close house contact with men infected with HAV. The route of transmission was not identified for 29 cases, and 88 patients (74%) required hospitalization. Among the cases, the following coinfections were already diagnosed: HIV 36 patients (30%), chronic hepatitis C virus (HCV) 4 patients (3%), and chronic hepatitis B virus (HBV) 2 patients (1.5%). During AHA diagnosis, some new sexually transmitted infections (STIs) were detected; syphilis eight patients (6.7%), HIV/syphilis seven patients (6%), HIV//HCV/syphilis one patient, and acute retroviral syndrome/Shigella flexneri one patient. Overall, AHA outbreak in Poland in 2017 affected primarily men who have sex with men (MSM) and was connected with oral–anal sexual contacts, and the majority of patients did not have HAV vaccination. These results show a clear need for routinely offering HAV vaccination to at-risk populations and that awareness among health-care workers about HAV sexual transmission may help introduce prevention methods.

Low immune response rate of HIV-infected patients to a single injection of hepatitis A vaccine

OBJECTIVES

We aimed to evaluate the immune response of HIV-1 positive patients to a single injection of HAV vaccine in a context of vaccine shortage during the 2017 European outbreak.

METHODS

We retrospectively enrolled all HIV-1 positive patients vaccinated by a single injection of HAV vaccine Vaqta 50®. HAV serology was performed before and>30 days after the vaccine injection.

RESULTS

Among the 73 patients, HIV-1 viral load was≤50 copies/mL in 93.2% of the cases. Medians of CD4 and median ratio of T CD4/CD8 cells were 658/mm³ and 0.9, respectively. A low immune response rate (59.7%) was observed among the patients. Responders had a significantly higher CD4/CD8 cell ratio than non-responders.

CONCLUSIONS

A serologic control should be recommended in this population in the event of a single injection vaccination schedule. During routine follow-up, and prior to any untoward event, physicians should assess the vaccination coverage of HIV-infected patients.

A description of a hepatitis A outbreak in men who have sex with men and public health measures implemented in Seine-Maritime department, Normandy, France, 2017

BACKGROUND

In 2016-2017, a European-wide circulation of genotype IA hepatitis A virus was responsible for hepatitis A outbreaks in men who have sex with men (MSM). This study aimed to describe the outbreak investigation in Seine-Maritime department (France) and the control measures implemented accordingly.

METHODS

Outbreak description used data from mandatory reporting and enhanced surveillance of male cases. Confirmed case was genotype IA isolated, possible cases had no reported genotype information. Targeted control measures included communication on sexual practices at risk of hepatitis A transmission and two vaccination campaigns in April 2017 and January 2018. Characteristics of cases and vaccinees were described. We reported the best communication channel for relaying outbreak information and control measures based on the monitoring of social network activities and feedback from vaccinees.

RESULTS

During the outbreak period (December 2016 to December 2017), a total of 48 confirmed outbreak cases and 30 possible outbreak cases were notified. Among them, 69 were male (88%). Two epidemic waves were observed. Cases encountered their partners through gay-dating apps (54%) and in one specific sauna (62%). In response to the outbreak, two vaccination campaigns were deployed. A total of 156 MSM were vaccinated, of whom 56 in a truck parked beside the sauna. Most of the vaccinees had been informed about the campaign through dating apps (44%). Community-based organizations involved in sexual health promotion and other gay social media were very proactive in sharing information about the outbreak and promoting the vaccination campaign through their social media account and also on site (gay venues). Vaccinees reported the same sexual practices at risk of hepatitis A transmission as cases.

CONCLUSIONS

In response to this massive hepatitis A outbreak that affected mostly MSM in Seine-Maritime department, vaccination campaign remained the cornerstone of prevention. Prevention officers from the community-based organization played a key role in vaccination promotion. Gay-dating apps and outdoor sessions of vaccination allowed to effectively reach MSM. Cost-effectiveness studies might analyze the interest of a continuous sexual health promotion including vaccination against hepatitis A in MSM through dating apps and social networks.

Co-Occurrence of Hepatitis A Infection and Chronic Liver Disease

Hepatitis A virus (HAV) infection occasionally leads to a critical condition in patients with or without chronic liver diseases. Acute-on-chronic liver disease includes acute-on-chronic liver failure (ACLF) and non-ACLF. In this review, we searched the literature concerning the association between HAV infection and chronic liver diseases in PubMed. Chronic liver diseases, such as metabolic associated fatty liver disease and alcoholic liver disease, coinfection with other viruses, and host genetic factors may be associated with severe hepatitis A. It is important to understand these conditions and mechanisms. There may be no etiological correlation between liver failure and HAV infection, but there is an association between the level of chronic liver damage and the severity of acute-on-chronic liver disease. While the application of an HAV vaccination is important for preventing HAV infection, the development of antivirals against HAV may be important for preventing the development of ACLF with HAV infection as an acute insult. The latter is all the more urgent given that the lives of patients with HAV infection and a chronic liver disease of another etiology may be at immediate risk.

Effectiveness of hepatitis A vaccination among people living with HIV in Taiwan: Is one dose enough?

BACKGROUND

Single dose hepatitis A virus (HAV) vaccine had been proven its efficacy in immunocompetent but not immunocompromised hosts. We aim to investigate the effectiveness of one dose versus 2 doses HAV vaccine among people living with HIV (PLHIV).

METHOD

We conducted a 1:1 single center retrospective case-control study for PLHIV in Northern Taiwan. Case patients were those who received single dose HAV vaccine and controls were those who completed standard 2 doses HAV vaccine. Nationwide campaign of single dose HAV vaccine had been practiced for high risk population including PLHIV and those who had newly diagnosed sexually transmitted diseases.

RESULTS

During February 2016 and December 2017, 90 cases received single dose HAV vaccine provided while the other 90 age-matched controls received 2 doses vaccine were enrolled. We found more injection drug users (22.22% vs. 1.11%, p < 0.0001), more co-infection with viral hepatitis C (28.89% vs. 5.56%, p < 0.0001), and history of syphilis infection (56.67% VS 30%, p = 0.0003) in single dose group than 2 doses group. Seroconversion rate at one year was significantly higher in 2 doses group (97.78% vs 56.67%, p < 0.0001). Among single dose group, people with hepatitis B or C virus co-infection (HBV: p = 0.02, aOR: 0.03, 95% CI: 0.002-0.55; HCV: p = 0.002, aOR: 0.22, 95% CI: 0.08-0.58) were less likely to achieve seropositivity, while those who had higher CD4 count at baseline and one year, had better response to vaccine.

CONCLUSION

Two doses HAV vaccine is necessary among PLHIV to achieve sustained seroresponse rather than single dose.

Sexual behaviour and poor hygiene are related to recent hepatitis a virus community outbreaks

OBJECTIVES

there has been a global increase in the incidence of hepatitis A infection. The aim of this study was to examine the characteristics of the increase in our region and the degree of adherence to the recommended hygienic measures after discharge from hospital.

METHODS

demographic, clinical and biochemical variables were collected from patients with acute hepatitis A in our health area. The patients were grouped as follows: January 2010 to December 2016 (historical cohort) and January 2017 to October 2017 (recent cohort). A phylogenetic analysis was also performed in the recent cohort. One month after discharge, bacterial growth was evaluated by a culture of the dominant hand imprint and were compared with a control group.

RESULTS

a total of 110 cases were registered with a median age of 36.3 years (range 3-89) and 77.3 % were male. The incidence was 0.82/100,000 inhabitants/year and 22.75/100,000 inhabitants/year in the historical and recent cohorts, respectively. Patients in the recent cohort were more frequently male (52.6 % vs. 82.4 %, p = 0.008) and younger (51.7 [3-89] vs. 33.4 [4-74] years, p < 0.001). In addition, 63.8 % of the recent cohort were men who had sex with other men and had unsafe sexual practices (37.5 %). Phylogenetic analysis showed a predominance of genotype A and a high frequency of the VRD 521-2016 sequence. A higher growth of enterobacteria was observed in patients with hepatitis A compared to the control group (7.3 % vs. 1.2 %, p = 0.005), despite specific hygienic measures given at discharge.

CONCLUSIONS

a recent outbreak of hepatitis A in our area was related with gender, younger age and sexual practices. Hepatitis A infected subjects showed a poor adherence to hygienic measures. Our data suggests the need for policies that encourage preventive actions, particularly vaccination in this high-risk group.

Characteristics of acute hepatitis A virus infection before and after 2001: A hospital-based study in Tokyo, Japan

BACKGROUND AND AIM

The incidence of acute hepatitis A [AH (A)] is decreasing because of improvements in hygiene; however, cases of sporadic severe hepatitis are still being reported. We assessed the epidemiology of AH (A) in Japan.

METHODS

This was a hospital-based retrospective study, in which 126 AH (A) patients (96 men [76%], median age 39 [range, 19-66] years) were enrolled. Patients diagnosed with AH (A) before 2001 (n = 79) and after 2001 (n = 47) were compared.

RESULTS

The incidence of AH (A) showed peaks in 1990, 1999, and 2018. After 2001, one patient had hepatitis B virus, four had human immunodeficiency virus, and three had syphilis coinfections. Before and after 2001, HAV was transmitted, respectively, by raw oysters (28% and 26%), overseas travel (19% and 28%), and sexual contact (0% and 19%) (P < 0.01). The frequencies of symptoms were appetite loss (51% and 32%), fever (63% and 81%), and diarrhea (3% and 13%) (all P < 0.05), respectively. On admission, the median levels of alanine aminotransferase (1455 and 3069 U/L) and γ-glutamyl transpeptidase (221 and 345 U/L) were significantly higher (P < 0.01), and the prothrombin time (77.5% and 65.9%) and platelet count (22.7 and 16.4 × 10/μL) were significantly lower after 2001 (P < 0.05). A time to normalization of the bilirubin level ≥ 30 days was associated with older age and a diagnosis of AH (A) after 2001.

CONCLUSIONS

Outbreaks and severe AH (A) cases due to sexual transmission have been reported recently. It is necessary to examine their sexual behavior and other sexual infection.

Liver Disease in Human Immunodeficiency Virus Infection

Liver disease in human immunodeficiency virus (HIV) remains a main cause of morbidity and mortality. Liver-related morbidity and mortality can be caused by multiple etiologic factors, including opportunistic infections, direct and indirect effects of antiretrovirals, direct and indirect effects of HIV, and viral hepatitides. These factors present with varied liver pathophysiologic mechanisms that lead to abnormalities in liver enzymes and synthetic function test, followed by distinct clinical presentations. This article elucidates the direct effects on HIV in the liver and explores the diagnostic and management challenges in patients with HIV in the era of highly active antiretroviral treatment.

Hepatitis A incidence, seroprevalence, and vaccination decision among MSM in Amsterdam, the Netherlands

BACKGROUND

Several outbreaks of Hepatitis A virus (HAV) were recently documented among men who have sex with men (MSM) in Europe. We investigated the HAV incidence among MSM in Amsterdam, the Netherlands; and HAV seroprevalence and HAV vaccination decision among MSM visiting the Sexually Transmitted Infection (STI) clinic in Amsterdam.

METHODS

Using surveillance data from 1992 to 2017 of MSM with acute HAV in Amsterdam, we estimated the incidence by calendar year and age. We explored HAV seroprevalence by calendar year and age, determinants for HAV seropositivity, and opting-in/out for HAV vaccination using data collected among MSM that visited the STI clinic between 2006 and 2017 and were included in a nationwide Hepatitis B virus (HBV) vaccination programme. Offering HAV vaccination at the STI clinic differed over three consecutive periods: not offered, offered for free, or offered for 75 euros. Logistic regression analyses were used to explore determinants.

RESULTS

HAV incidence increased in 2016/17 after 4 years of absence and peaked in MSM around 35 years of age. Among MSM visiting the STI clinic, HAV seroprevalence was 37% (95%CI = 35-40%), which was constant over the period 2006-2017, and increased with age (p < 0.001). Determinants for HAV seropositivity in multivariable analysis were: older age (p < 0.001), originating from an HAV endemic country (p < 0.001), and being HBV seropositive (p = 0.001). MSM opted-in more frequently when HAV vaccination was offered for free versus paid (89% versus 11%, respectively; p < 0.001). Younger MSM were less inclined to vaccinate when payment was required (p = 0.010). Post-hoc analyses showed that 98% versus 46% of MSM visiting the Amsterdam STI clinic would be protected against HAV infection if HAV vaccination was offered for free or for 75 euros, respectively.

CONCLUSIONS

The MSM population of Amsterdam is vulnerable to a new HAV outbreak. We strongly recommend that MSM have access to free hepatitis A vaccination.