% Reduction in probability to acquire HBV infection among those receiving PrEPĪssortative mixing in steady or casual partnerships, respectivelyįactor increasing CAI frequency before 2002 compared to 2002 and thereafter % Reduction probability to acquire HBV due to HBV-related antiretrovirals for HIV Relative transmissibility if virally suppressed, compared to inactive chronic HBV Transmissibility decompensated cirrhosis, HCC Relative transmissibility compensated cirrhosis, compared to inactive chronic HBV Relative transmissibility active CHB, compared to inactive chronic HBV ![]() Relative transmissibility acute HBV, compared to inactive chronic HBV Probability HBV transmission per act CAI if infected has inactive chronic HBV Probability HBV transmission per act CAI if infected in state i = 1, 2, ⋯, 6, T Rate of entry into and exit out of population, per year % Virally suppressed among treated, from 2012 onwards % Virally suppressed among treated, until 2011 % of diagnosed under treatment, from 2012 onwards % of diagnosed under treatment, until 2011 Treatment rate active CHB, compensated cirrhosis, per year HBV-related death rate for those treated, per year Progression rate treated (T) to HCC (W 8), per year % new HBV infections notified during acute phase HBV clearance rate from compensated cirrhosis, per year HBV clearance rate from chronic infection, per year Transition rate out of acute infection, per year Probability acute infection progresses to chronic Progression from decompensated cirrhosis to HCC, per yearĭeath rate from compensated cirrhosis, per yearĭeath rate from decompensated cirrhosis, per year Progression from compensated cirrhosis to HCC, per year Progression from inactive to HCC, per year Progression from active CHB to HCC, per year Progression rate compensated to decompensated cirrhosis, per year Progression rate active CHB to compensated cirrhosis, per year Progression rate inactive to active CHB, per year Progression rate active CHB to inactive, per year ![]() HBV testing rates were derived from the National Database of Sexual Health Centres. The HBV vaccination rate among MSM was estimated by fitting the model to data on the number of MSM who received their third dose of HBV vaccination in each year (data from the National HBV Vaccination Programme for Risk Groups see, Supplement Table S2 and Fig. ![]() Uninfected MSM in the Netherlands can receive HBV vaccination free of charge from 2003 onwards, and with three vaccine doses they are immune for life. Parameters relating to sexual activity before the pandemic were estimated based on data from the Amsterdam Cohort Study on HIV among MSM in Amsterdam (Supplement Table S1). Briefly, the model accounts for HBV transmission among MSM through condomless anal intercourse with steady or casual partners (Supplement Fig. We used a deterministic compartmental model that we developed earlier to investigate the impact of risk-group HBV vaccination of MSM. In this study, we considered changes in the numbers of steady and casual partners during the pandemic as the principal indicator of COVID-19-related changes in sexual activity and investigated how these changes combined with modifications in HBV testing and HBV vaccination could affect HBV transmission among MSM, using a mathematical model. On the other hand, MSM have reported lower levels of sexual activity during the pandemic, , and that could decrease HBV transmission. For similar reasons, there has also been a decline in HBV testing, that, combined with reduced HBV vaccination, could contribute to increased HBV transmission. This reduction is a result of a combination of factors, including lockdowns and other restrictive measures that, for example, made on site outreach impossible, the disruptions in healthcare services, and the reluctance of some individuals to visit healthcare facilities. The COVID-19 pandemic, however, has disrupted this increasing trend and the number of HBV vaccinations administered via the programme since March 2020 has been considerably lower than before. Major efforts among national and regional public health organisations have resulted in a steadily increasing number of HBV vaccinations among MSM over the years. However, the programme for risk groups continues, since it targets sexually active individuals, who are not yet protected via the vaccination of newborn babies. Since 2011, there is also a national programme for HBV vaccination among all newborn babies. Men who have sex with men (MSM) and sex workers are currently included in the programme. In 2002, the National Hepatitis B Vaccination Programme for Risk Groups was initiated in the Netherlands providing vaccination against hepatitis B virus (HBV) for population subgroups at increased risk of acquiring HBV.
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