Amy Matser

• Doctor of Philosophy
• Professor of applied sciences, datadriven public safety at NIPV, Dutch National Institute for Public Safety

Source and contact tracing (SCT) is a core public health measure that is used to contain the spread of infectious diseases. It aims to identify a source of infection, and to advise those who have been exposed to this source. Due to the rapid increases in incidence of COVID-19 in the Netherlands, the capacity to conduct a full SCT quickly became ins...

Background This study explored the expected impact of two hypothetical HIV cure scenarios on quality of life, sexual satisfaction, and stigma among people with HIV and key populations (i.e., partners and communities of people with HIV and men who have sex with men without HIV) in the Netherlands. Methods A cross-sectional survey was conducted amon...

Background: Syndromic surveillance systems are crucial for the monitoring of population health and the early detection of emerging health problems. Internationally, there are numerous established systems reporting on different types of data. In the Netherlands, the Nivel syndromic surveillance system provides real-time monitoring on all diseases an...

Background Little is known about the effect of HCV treatment on sexual risk behaviour among men who have sex with men (MSM) with HIV by treatment type (IFN-based vs DAA-based). Setting MSM with HIV and recently acquired HCV infection enrolled in the observational MOSAIC cohort. Methods Using data from 2009-2018, we evaluated risk behaviour throug...

Objective This study explored the expected impact of two hypothetical HIV cure scenarios on quality of life (QoL), sexual satisfaction, and stigma among people with HIV (PHIV) and key populations (i.e., partners of PHIV, family members, friends and other contacts, and MSM without HIV) in the Netherlands. Design A cross-sectional survey was conducte...

UNSTRUCTURED The present article introduces the Nivel Syndromic Surveillance system (NSSS), emphasizing its role in providing “real-time” information on infectious diseases and various health problems at the population level, in the Netherlands. Utilizing data from general practitioners’ (GPs) electronic health records (EHRs), the system allows for...

Background Syndromic surveillance systems are crucial for the monitoring of population health and the early detection of emerging health problems. Internationally, there are numerous established systems reporting on different types of data. In the Netherlands, the Nivel syndromic surveillance system provides real-time monitoring on all diseases and...

After 3 years of its introduction to humans, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared as endemic. Little is known about the severity of the disease manifestation that future infections may cause, especially when reinfections occur after humoral immunity from a previous infection or vaccination has waned. Such k...

During the COVID-19 pandemic, levels of seasonal influenza virus circulation were unprecedentedly low, leading to concerns that a lack of exposure to influenza viruses, combined with waning antibody titres, could result in larger and/or more severe post-pandemic seasonal influenza epidemics. However, in most countries the first post-pandemic influe...

The Dutch government introduced the CoronaMelder smartphone application for digital contact tracing (DCT) to complement manual contact tracing (MCT) by Public Health Services (PHS) during the 2020–2022 SARS-CoV-2 epidemic. Modelling studies showed great potential but empirical evidence of DCT and MCT impact is scarce. We determined reasons for test...

We assessed the predictive capacity of the HCV-MOSAIC risk score, originally developed for primary early HCV infection, as a screening tool for HCV reinfection in 103 men who have sex with men (MSM) with HIV using data from the MOSAIC cohort, including MSM with HIV/HCV-coinfection who became reinfected (cases, n = 27) or not (controls, n = 76) duri...

Biomedical HIV-prevention strategies (BmPS) among men who have sex with men (MSM), such as pre-exposure prophylaxis (PrEP) and viral load sorting (VLS), are essential but relatively new and their uptake gradual. Using an extension of the causal attitude network approach, we investigated which beliefs are related to uptake of PrEP and VLS at each ti...

OBJECTIVE. Clinical trials have shown that doxycycline as post-exposure prophylaxis after sexual contact (doxy-PEP) prevents sexually transmitted bacterial infections (STI). We investigated current awareness about informal use of antibiotics as pre- and post- exposure prophylaxis to prevent STI (STI-PrEP/PEP) among men who have sex with men (MSM)....

Aims We measured the association between a history of incarceration and HIV positivity among people who inject drugs (PWID) across Europe. Design, Setting and Participants This was a cross‐sectional, multi‐site, multi‐year propensity‐score matched analysis conducted in Europe. Participants comprised community‐recruited PWID who reported a recent i...

Background Daily and event-driven HIV pre-exposure prophylaxis (PrEP) with oral tenofovir-emtricitabine is highly effective to prevent HIV in men who have sex with men (MSM). PrEP care generally consists of in-clinic monitoring every 3 months that includes PrEP dispensing, counseling, and screening for HIV and sexually transmitted infections (STIs)...

BACKGROUND Daily and event-driven HIV pre-exposure prophylaxis (PrEP) with oral tenofovir-emtricitabine is highly effective to prevent HIV in men who have sex with men (MSM). PrEP care generally consists of in-clinic monitoring every 3 months that includes PrEP dispensing, counseling, and screening for HIV and sexually transmitted infections (STIs)...

Background. The Dutch government introduced the CoronaMelder smartphone application for digital contact tracing (DCT) to complement manual contact tracing (MCT) by Public Health Services (PHS) during the 2020-2022 SARS-CoV-2 epidemic. Modelling studies showed great potential but empirical evidence of DCT and MCT impact is scarce. Methods. We determ...

Objectives: A previous study showed higher prevalence of Escherichia coli expressing extended-spectrum β-lactamases (ESBL-Ec) among men who have sex with men (MSM) in Amsterdam, the Netherlands, compared to the general Dutch population. We here genetically characterised the ESBL-Ec isolates and investigated whether the increased prevalence could b...

Background: As highly effective therapy against hepatitis C virus (HCV) infection is available with rapid uptake, there is newfound optimism for HCV elimination. Nevertheless, certain key populations have a high risk of HCV reinfection, in particular men who have sex with men (MSM) in Western European countries. Modelling data indicate that HCV el...

Respondent-driven sampling (RDS) uses the social network of participants to sample people of populations that can be challenging to engage. While in this context RDS offers improvements on standard sampling methods, it does not always generate a sufficiently large sample. In this study we aimed to identify preferences of men who have sex with men (...

Background Suriname, a country endemic for dengue virus (DENV), is a popular destination for Dutch travellers visiting friends and relatives and tourist travellers. Chikungunya and Zika virus (CHIKV, ZIKV) were introduced in 2014 and 2015, respectively. Data on infection risks among travellers are limited. Aim We aimed to prospectively study incid...

Introduction In the 2022 multicountry mpox (formerly named monkeypox) outbreak, several countries offered primary preventive vaccination (PPV) to people at higher risk for infection. We study vaccine acceptance and its determinants, to target and tailor public health (communication-) strategies in the context of limited vaccine supply in the Nether...

Background: As highly effective therapy against hepatitis C virus (HCV) infection is available with rapid uptake, there is newfound optimism for HCV elimination. Nevertheless, certain key populations have a high risk of HCV reinfection, in particular men who have sex with men (MSM) in Western European countries. Modelling data indicate that HCV eli...

To reappraise pre-exposure prophylaxis (PrEP) eligibility criteria towards the men who have sex with men (MSM) with highest HIV-risk, we assessed PrEP need (i.e. HIV-risk) using Amsterdam Cohort Studies data from 2011-2017 for all non-PrEP using MSM. Outcomes were incident HIV-infection and newly-diagnosed anal STI. Determinants were current PrEP e...

Background Testing and Contact Tracing (TCT) was a core strategy in the fight against the spread of SARS-CoV-2. However, little is known about the real-world effectiveness of TCT for COVID-19. Because time is an important conditional factor, we aim to study timeliness of TCT in the Netherlands, and its determinants. Methods We used routine COVID-1...

Objectives We studied the effects of restrictions related to the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2; coronavirus disease 2019 [COVID‐19]) pandemic on the use of sexual healthcare and pre‐exposure prophylaxis (PrEP) and on the incidence of sexually transmitted infections (STIs) among men who have sex with men (MSM) in a pros...

Introduction In the global monkeypox outbreak primary preventive vaccination is offered to people at higher risk for infection. We study vaccine acceptance and its determinants, to target and tailor public health (communication-)strategies in the context of limited vaccine supply in the Netherlands. Methods. Online survey in a convenience sample of...

Background Chemoprophylaxis and anti-mosquito measures are key to preventing malaria in travelers. Long-term travelers are at higher risk than short-term travelers, but their adherence to preventive measures is lower. Our aim was to determine malaria exposure risks and predictors for adherence to malaria-preventive measures in long-term travelers....

Background During the COVID-19 pandemic, the number of hepatitis B virus (HBV) vaccinations among men who have sex with men (MSM) has been considerably lower than before the pandemic. Moreover, less frequent HBV testing and a reduction in numbers of sex partners have been reported. We assessed the impact of these COVID-19-related changes on HBV tra...

Men who have sex with men (MSM) initiating human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP) may increase condomless anal sex (CAS) and number of partners, and, consequently, more often acquire sexually transmitted infections (STIs). Using data from the Amsterdam Cohort Studies, we compared sexual behavior and STI among MSM after P...

Background: Worldwide, efforts are being made to stop the COVID-19 pandemic caused by SARS-CoV-2. Contact tracing and quarantining are key in limiting SARS-CoV-2 transmission. Mathematical models have shown that the time between infection, isolation of cases, and quarantining of contacts are the most important components that determine whether the...

Background During the first two years of the COVID-19 pandemic, the circulation of seasonal influenza viruses was unprecedentedly low. This led to concerns that the lack of immune stimulation to influenza viruses combined with waning antibody titres could lead to increased susceptibility to influenza in subsequent seasons, resulting in larger and m...

Background: During the COVID-19 pandemic, the disruption in care for sexually transmitted infections (STIs) and the social distancing measures have led to reductions in STI testing and sexual behavior. We assessed the impact of these COVID-19-related changes on transmission of C. trachomatis (CT) and N. gonorrhoeae (NG) among men who have sex with...

Introduction Most COVID-19 symptoms are non-specific and also common in other respiratory infections. We aimed to assess which symptoms are most predictive of a positive test for SARS-CoV-2 in symptomatic people of the general population who were tested. Methods We used anonymised data of all SARS-CoV-2 test results from the Public Health Service...

Introduction: The uptake of pre-exposure prophylaxis (PrEP) against HIV is low among young men who have sex with men (MSM) in the Netherlands. Studying the intention to use PrEP among non-PrEP using young and older MSM can guide health authorities in developing new prevention campaigns to optimize PrEP uptake. Methods: We investigated the sociod...

As individual sexual behavior is variable over time, the timing of interventions might be vital to reducing HIV transmission. We aimed to investigate transitions between HIV risk levels among men who have sex with men (MSM), and identify determinants associated with behavior change. Participants in a longitudinal cohort study among HIV-negative MSM...

To assess whether HIV-negative men who have sex with men (MSM) have realistic views of the current implications of living with HIV, we compared data of 950 tested HIV-negative and 122 never-tested MSM on anticipated consequences of an HIV-infection to the actual experiences of 438 MSM living with HIV. Data were collected with a self-reported, web-b...

Objectives: Pre-exposure prophylaxis (PrEP) use may influence sexual behaviour and transmission of STIs among men who have sex with men (MSM). We aimed to quantify the distribution of STI diagnoses among MSM in the Netherlands based on their sexual behaviour before and after the introduction of PrEP. Methods: HIV-negative MSM participating in a pro...

Background: Few robust longitudinal data on long-term COVID-19 symptoms are available. We evaluated symptom onset, severity and recovery across the full spectrum of disease severity, up to one year after illness onset. Methods: The RECoVERED Study is a prospective cohort study based in Amsterdam, the Netherlands. Participants aged≥18 years were...

Aims To test whether recreational drug use (RDU) and sexualized drug use (SDU) changed in the Amsterdam metropolitan area between 2008 and 2018 and quantify associations of SDU with condomless anal sex (CAS), recent human immunodeficiency virus (HIV) or sexually transmitted infections (STI) among human immunodeficiency virus (HIV)-negative men who...

Pre-exposure prophylaxis (PrEP) use may influence sexual behavior, and sexually transmitted infections (STI) incidence among men who have sex with men (MSM). Here, we aimed to quantify how STI diagnoses are distributed among MSM in the Netherlands based on their sexual behavior using Gini coefficients, and examined possible changes in these coeffic...

Background Fear of COVID-19 infection and the response measures have affected sexual behaviours of men who have sex with men (MSM) and access to care for sexually transmitted infections (STI). We investigated whether these changes resulted in increased or decreased STI transmission among MSM. Methods We developed a mathematical transmission model...

BACKGROUND Worldwide, efforts are being made to stop the COVID-19 pandemic caused by SARS-CoV-2. Contact tracing and quarantining are key in limiting SARS-CoV-2 transmission. Mathematical models have shown that the time between symptom onset and isolation of cases and isolation of contacts are the most important components that determine whether th...

HIV risk perception plays a crucial role in the uptake of preventive strategies. We investigated how risk perception and its determinants changed between 1999 and 2018 in an open, prospective cohort of 1323 HIV-negative men who have sex with men (MSM). Risk perception, defined as the perceived likelihood of acquiring HIV in the past 6 months, chang...

Background Risk-group HBV vaccination for men who have sex with men (MSM) was introduced in the Netherlands in 2002, followed by universal infant vaccination in 2011, that will enable termination of risk-group vaccination over time. The introduction of pre-exposure prophylaxis (PrEP) for HIV prevention might result in increased HBV testing and vacc...

Background: Few longitudinal data on COVID-19 symptoms across the full spectrum of disease severity are available. We evaluated symptom onset, severity and recovery up to nine months after illness onset. Methods: The RECoVERED Study is a prospective cohort study based in Amsterdam, the Netherlands. Participants aged>18 years were recruited followin...

Background and aims: Major declines in HIV and hepatitis C and B virus (HCV/HBV) incidence among people who inject drugs (PWID) have been attributed to early implementation of harm-reduction programs (HRP) in the Netherlands, but alternative factors such as selective mortality and demographic and drug market shifts over time probably contributed t...

Background Extended spectrum β-lactamase Enterobacteriaceae (ESBL-E) might be sexually transmitted. Men who have sex with men (MSM) have different sexual behavior than the general population and thus might be at risk for ESBL-E carriage. We determined the prevalence of ESBL-E carriage and its association with sexual behavior among MSM in Amsterdam,...

Background Optimising HIV pre-exposure prophylaxis (PrEP) provision requires insight into preferences of PrEP regimens and PrEP discontinuation. We assessed regimen switching and discontinuation and their determinants among men who have sex with men (MSM) participating in the Amsterdam PrEP demonstration project. Methods Between 3-August-2015 and...

Objective: To investigate the impact of Dutch COVID-19 restrictions on sexual behavior and HIV/STI acquisition among men who have sex with men (MSM) participating in the Amsterdam Cohort Studies (ACS) on HIV in Amsterdam. Methods: ACS participants complete a questionnaire on sexual behaviour and are tested for HIV/STI biannually. They may also b...

A key unsolved question in the current coronavirus disease 2019 (COVID-19) pandemic is the duration of acquired immunity. Insights from infections with the four seasonal human coronaviruses might reveal common characteristics applicable to all human coronaviruses. We monitored healthy individuals for more than 35 years and determined that reinfecti...

Introduction: Before 2019, availability of affordable HIV Pre-exposure prophylaxis (PrEP) was limited in the Netherlands. Consequently, some men who have sex with men (MSM) and transgender persons (TGP) obtained PrEP informally, i.e. without a prescription. Methods: Between September 2017 and August 2018, we enrolled informal PrEP users in a coh...

The current study sought to identify types of group sex acts among HIV-negative men who have sex with men (MSM) and assess their association with different sexual risk behaviors using cross-sectional data of group sex acts reported during 6 waves (2015–2018) of the Amsterdam MSM Cohort Study. Latent class analysis was performed to identify group se...

Background: HIV-positive men who have sex with men (MSM) are at high risk of hepatitis C virus (HCV) reinfection following clearance of HCV, but risk factors specifically for reinfection have never been comprehensively assessed. Methods: Using data from a prospective observational cohort study among HIV-positive MSM with an acute HCV infection (...

In the current SARS-CoV-2 pandemic a key unsolved question is the quality and duration of acquired immunity in recovered individuals. This is crucial to solve, however SARS-CoV-2 has circulated for under five months, precluding a direct study. We therefore monitored 10 subjects over a time span of 35 years (1985-2020), providing a total of 2473 fol...

Objectives: We investigated changes in incidence rates of HIV and sexually transmitted infections (STI) and trends in sexual behavior in MSM from 2009-2017. Design: Open prospective cohort study. Methods: HIV-negative MSM enrolled in the Amsterdam Cohort Studies were included. Participants semiannually completed a questionnaire on sexual behav...

Background and aim: Men who have sex with men (MSM) are at high risk for both drug use and sexually transmitted infections (STI). We aimed to (1) identify subgroups of drug use during sex among MSM in Amsterdam and after classifying participants,(2) compare sexual behaviour and STI across groups. Design: Cross-sectional study. Latent class analy...

Background: Over-the-counter intra-vaginal lactic-acid containing douches are marketed as vaginal hygiene products that support optimal vaginal pH balance. We report the effect of a commercially available douche (Etos®) on the vaginal microbiota (VM) in a prospective study. Results: Twenty-five healthy women were recruited through advertisements...

Background Men who have sex with men (MSM) are at high risk for both drug abuse and sexually transmitted infections (STI). We aimed to identify subgroups of MSM in Amsterdam with distinctive patterns of drug use during sex and their association with sexual behavior and STI. Methods In this cross-sectional study, data from four different studies on...

Background Recreational drug use (RDU), particularly during sex, may contribute to human immunodeficiency virus (HIV) and sexually transmitted infections (STI) transmission by increasing sexual risk behaviour. We studied changes in RDU, including chemsex, and associations with condomless anal sex (CAS), HIV and STI among HIV-negative men who have s...

Background: Pre-exposure prophylaxis (PrEP) for HIV might induce risk compensation, defined as increased sexual risk behaviour leading to increased incidence of bacterial sexually transmitted infections (STIs). We examined the incidence of HIV, STIs, and sexual behaviour after initiating daily and event-driven PrEP. Methods: AMPrEP is a demonstr...

Background HIV and other sexually transmitted infections remain a burden on men who have sex with men in the era of effective combination antiretroviral therapy. New prevention efforts are therefore needed. One of these approaches is the current country-wide free condom distribution at gay bars with darkrooms and gay saunas in the Netherlands. This...

Changes in sexual risk behavior over the life course in men who have sex with men (MSM)can influence population-level intervention efficacy. Our objective was to investigate the impact of incorporating sexual trajectories describing long-term changes in risk levels on the reduction in HIV prevalence by pre-exposure prophylaxis (PrEP)among MSM. Base...

Background In the Netherlands, there are strong disparities in Chlamydia trachomatis (CT) prevalence between ethnic groups. The current study aims to identify whether socioeconomic status, sexual risk behavior and sexual healthcare seeking behavior may explain differences in CT seroprevalence between ethnic groups. Methods We used 2011–2014 baseli...

Objective Currently, HIV pre-exposure prophylaxis (PrEP) is not covered by health insurance in the Netherlands. We examined time trends in use of PrEP, characteristics of PrEP users, PrEP eligibility and intention to use PrEP among HIV-negative men who have sex with men (MSM) participating in the Amsterdam Cohort Studies (ACS). Design Prospective...

Calculation of the estimated number of expected PrEP users in Amsterdam, the Netherlands. (PDF)

Background: Deferral of men who have sex with men (MSM) from blood donation is highly debated. To assist in defining MSM donor deferral policies, we investigated their suitability to donate blood. Methods: We compared the antibody prevalence of 10 sexually and transfusion transmissible infections (TTI) among 583 MSM from the Amsterdam Cohort Stu...

Background: In response to the increased hepatitis C virus (HCV) prevalence recently found among participants of the Amsterdam pre-exposure prophylaxis demonstration project, we evaluated HCV prevalence over time and the performance of the HCV-MOSAIC risk score for detection of HCV infection in HIV-negative men who have sex with men (MSM) attendin...

Background Despite the considerable burden of helminth infections in developing countries and increasing international travel, little is known about the risks of infection for travelers. Objective We studied the attack and incidence rate of serology confirmed strongyloidiasis, filariasis, and toxocariasis among long-term travelers and associated f...

Post-travel questionnaire (in Dutch). (PDF)

Travel diary (in Dutch). (PDF)

Post-travel questionnaire (in English). (PDF)

Travel diary (in English). (PDF)

Dataset long-term travelers (de-identified). (XLSX)

HIV and other sexually transmitted infections remain a burden on men who have sex with men in the era of effective combination antiretroviral therapy. New prevention efforts are therefore needed. One of these approaches is the current country-wide free condom distribution at gay bars with darkrooms and gay saunas in the Netherlands. This study asse...

Objective: Sexual risk behaviour changes during a person's life course. Insights in sexual risk behaviour trajectories of MSM may provide starting points for the timing of HIV prevention methods. We aimed to study longitudinal trajectories of sexual risk behaviour predictive of HIV acquisition from sexual debut onwards. Design: A longitudinal st...

Background: The source of an infection is often unknown. To inform directed prevention measures, it is useful to know the location and partner type with the highest transmission risk. We developed a method to estimate infection risk of Neisseria gonorrhoeae per meeting location among men who have sex with men (MSM). Methods: In 2008-2009, we col...

Background: Prevention of hepatitis C virus (HCV) transmission among people who inject drugs (PWID) is critical to eliminating HCV in Europe. We estimate impact of current and scaled-up HCV treatment with and without scaling-up opioid substitution therapy (OST) and needle and syringe programmes (NSP) across Europe over the next 10 years. Methods:...

Introduction Men who have sex with men (MSM) constitute a risk group for sexual transmitted infections (STIs), including HIV. Despite counselling interventions, risk behaviour remains high. Syndemic theory holds that psychosocial problems often co-occur, interact and mutually reinforce each other, thereby increasing high risk behaviours and co-occu...

Introduction Of female visitors to the STI clinic in Amsterdam, 31% report use of vaginal cleansing products (including douches). Vaginal douching may negatively affect vaginal microbiota compositions (VM). We report the effect of intra-vaginal douching on the VM in a prospective study. Methods Through advertisements, we recruited 25 healthy women...

Introduction Syphilis incidence is rising in developed countries worldwide, and men who have sex with men (MSM) are disproportionally affected. Follow-up after treatment of syphilis is important as late complications (e.g. neurosyphilis), therapy failure and re-infections can occur, especially in HIV co-infected patients. Failure to complete follow...

Introduction Sexual behaviour changes during a person’s life course. Insights in sexual careers of men who have sex with men (MSM) may optimise timing of HIV prevention methods. Our objectives were to develop a behavioural risk score for HIV seroconversion and study trajectories of sexual behaviour over time. Methods Longitudinal data from the Ams...

Introduction In the Netherlands, there are strong disparities in Chlamydia trachomatis (CT) prevalence among ethnic groups. The highest prevalence is found among individuals from Surinamese descent. Previous research suggested that socio-economic status (SES) may be important in explaining these differences. In ethnic groups with high CT prevalence...

Background People who inject drugs (PWID) are disproportionally affected by the hepatitis C virus (HCV) infection. The efficacy of HCV treatment has significantly improved in recent years with the introduction of direct-acting antivirals (DAAs). However, DAAs are more costly than pegylated-interferon and ribavirin (PegIFN/RBV). We aimed to assess t...

Supplementary tables & graphs. (DOCX)

Background Men having sex with men (MSM) frequently use the Internet to find sex partners. We examined the association between unprotected anal intercourse (UAI) with partners dated online and with partners dated offline (met elsewhere), and examined whether differences can be explained by self-perceived HIV status of the index and knowledge of par...

The practice of unprotected anal intercourse (UAI) involves at least two partners. We examined the associations between insertive or receptive UAI and perceived HIV seroconcordance and partnership type in self-perceived HIV-negative and self-perceived HIV-positive men who have sex with men (MSM). MSM (age ≥ 18 years) were recruited for a cross-sect...

Decisions to use condoms are made within partnerships. We examined the associations between inconsistent or no condom use and individual and partnership characteristics. We also examined the relative importance of individual versus partnership factors. Cross-sectional study of heterosexual individuals enrolled from the sexually transmitted infectio...