In scenario 1, without a vaccination program, the model estimated 237,021 new HBV infections would occur over the lifetime of the 2 million annual STD clinic clients. These new infections would result in 71,106 acute hepatitis B cases and 14,221 cases of chronic HBV infection. Among people with acute hepatitis B, 1,138 would develop FLF, 137 would require liver transplantation, and 848 would die. Among those with chronic HBV infection 2,933 would develop cirrhosis, 917 would develop HCC, 121 would require liver transplantation, and 3,060 would die. The societal cost of HBV infections would be $1,587 million: $346 million in medical costs and $1,241 million in productivity losses ().
Hepatitis B vaccination at STD clinics: expected outcomes and economic implications among 2 million clients
In the first year of a national vaccination program (scenario 2), a total of 1.3 million clients would receive vaccination: 626,040 clients would receive a single dose, 306,360 clients would receive two doses, and 399,600 clients would receive three doses of vaccine. This level of vaccine coverage would prevent 105,828 of the new HBV infections expected without vaccination, a 45% reduction. Reduction in infection would avert 31,748 acute hepatitis B cases and resultant complications, including 508 FLF cases, 61 liver transplantations, and 378 deaths. In addition, 6,350 chronic HBV infections would be prevented, which would avert 1,309 cirrhosis cases, 410 HCC cases, 54 liver transplantations, and 1,366 deaths.
The first year of the vaccination program would require 2,708,400 doses of vaccine (including an estimated 10% wastage) and cost $138 million, including $95 million for vaccine and administration, $30.5 million for staff training and supervision, and $12.2 million for protocol development and vaccination record-keeping. In addition, clients' travel and time for vaccination would cost $45 million. HBV infections that occur despite the vaccination program would cost $879 million, including $192 million in medical costs and $687 million in productivity losses. The total cost of HBV infection and management with a vaccination program is $1,061 million (compared with $1,587 million without vaccination), yielding a net economic benefit of $526 million. If indirect costs of potential productivity losses were excluded from the analysis, the vaccination program would have a net cost of $28 million, or $263 per new HBV infection averted.
The net economic benefit was most sensitive to changes in the cohort age, risk of infection, proportion of clients receiving at least one dose, and mean daily wage—changing 11% to 17%, with a 10% change from base-case value of any of the parameters. Net economic benefit was relatively less sensitive to changes in vaccine efficacy, rates of receiving dose two and dose three among patients receiving dose one, prevalence of immunity from prior infection (anti-HBc prevalence), proportion of new infections with acute hepatitis B, lifetime risk of chronic HBV infection, annual rate of compensated cirrhosis among people with chronic HBV infection, and the annual discount rate; changing 1% to 9%, with a 10% change in each parameter (). Net economic benefit changed less than 1%, with a 10% change in each of the other parameters.
Sensitivity analyses: change in net economic benefit in response to 10% change in model parameter values from base casea
The net economic benefit without productivity losses was relatively more sensitive to all parameter values, with the lifetime risk of HBV infection, and the proportion of STD clients who accept the first dose of vaccine, as the most influential inputs. In a scenario in which lost productivity due to illness was not considered, the net economic benefits increased by 56%, with a 10% increase of either parameter from baseline levels. We determined that medical cost savings alone would be sufficient to compensate for program-related costs if either the lifetime risk of infection among susceptible patients increased by 3% (to 17.7%) or the proportion of STD clinic clients who accept the first dose of vaccine increased by 13% (to 87.3%).