Health economic assessment of universal immunization of toddlers against Hepatitis A Virus (HAV) in Mexico

Hepatitis A virus infection

Hepatitis A is a vaccine-preventable infection caused by the hepatitis A virus (HAV). Over 150 million new infections of hepatitis A occur annually. HAV causes an acute inflammatory reaction in the liver that usually resolves spontaneously without chronic sequelae. However, up to 20% of patients experience a prolonged or relapsed course and <1% experience acute liver failure. Host factors, such as immunological status, age, pregnancy and underlying hepatic diseases, can affect the severity of disease. Anti-HAV IgG antibodies produced in response to HAV infection persist for life and protect against re-infection; vaccine-induced antibodies against hepatitis A confer long-term protection. The WHO recommends vaccination for individuals at higher risk of infection and/or severe disease in countries with very low and low hepatitis A virus endemicity, and universal childhood vaccination in intermediate endemicity countries. To date, >25 countries worldwide have implemented such programmes, resulting in a reduction in the incidence of HAV infection. Improving hygiene and sanitation, rapid identification of outbreaks and fast and accurate intervention in outbreak control are essential to reducing HAV transmission.

[Cost-effectiveness of universal childhood vaccination against hepatitis A in Spain: a dynamic approach]

OBJECTIVE

To evaluate the cost-effectiveness of infant universal vaccination against hepatitis A in Spain.

METHOD

Using a dynamic model and decision tree model, a cost-effectiveness analysis was performed to compare three vaccination strategies against hepatitis A: non-vaccination strategy versus universal childhood vaccination of hepatitis A with one or two doses. The perspective of the study was that of the National Health System (NHS) and a lifetime horizon was considered. Both costs and effects were discounted at 3% per year. Health outcomes were measured in terms of quality adjusted life years (QALY) and the cost-effectiveness measure used was the incremental cost-effectiveness ratio (ICER). In addition, deterministic sensitivity analysis by scenarios was performed.

RESULTS

In the particular case of Spain, with low endemicity for hepatitis A, the difference in health outcomes between vaccination strategies (with 1 or 2 doses) and non-vaccination are practically non-existent, terms of QALY. In addition, the ICER obtained is high, exceeding the limits of willingness to pay from Spain (€22,000-25,000/QALY). The deterministic sensitivity analysis showed that the results are sensitive to the variations of the key parameters, although in no case the vaccination strategies are cost-effective.

CONCLUSIONS

Universal infant vaccination strategy against hepatitis A would not be a cost-effective option from the NHS perspective in Spain.

Inclusion of Additional Unintended Consequences in Economic Evaluation: A Systematic Review of Immunization and Tuberculosis Cost-Effectiveness Analyses

OBJECTIVE

Our objective was to review economic evaluations of immunization and tuberculosis to determine the extent to which additional unintended consequences were taken into account in the analysis and to describe the methodological approaches used to estimate these, where possible.

METHODS

We sourced the vaccine economic evaluations from a previous systematic review by Nymark et al. (2009-2015) and searched PubMed/MEDLINE and Embase from 2015 to 2019 using the same search strategy. For tuberculosis economic evaluations, we extracted studies from 2009 to 2019 that were published in a previous review by Siapka et al. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. Studies were classified according to the categories and subcategories (e.g., herd immunity, non-specific effects, and labor productivity) defined in a framework identifying additional unintended consequences by Nymark and Vassall. Where possible, methods for estimating the additional unintended consequences categories and subcategories were described. We evaluated the reporting quality of included studies according to the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) extraction guideline.

RESULTS

We identified 177 vaccine cost-effectiveness analyses (CEAs) between 2009 and 2019 that met the inclusion criteria. Of these, 98 included unintended consequences. Of the total 98 CEAs, overall health consequence categories were included 73 times; biological categories: herd immunity 43 times; pathogen response: resistance 15 times; and cross-protection 15 times. For health consequences pertaining to the supply-side (health systems) categories, side effects were included five times. On the nonhealth demand side (intrahousehold), labor productivity was included 60 times. We identified 29 tuberculosis CEAs from 2009 to 2019 that met the inclusion criteria. Of these, six articles included labor productivity, four included indirect transmission effects, and one included resistance. Between 2009 and 2019, only 34% of tuberculosis CEAs included additional unintended consequences, compared with 55% of vaccine CEAs.

CONCLUSIONS

The inclusion of additional unintended consequences in economic evaluations of immunization and tuberculosis continues to be limited. Additional unintended consequences of economic benefits, such as those examined in this review and especially those that occur outside the health system, offer valuable information to analysts. Further work on appropriate ways to value these additional unintended consequences is still warranted.

Economic evaluation of a publicly funded hepatitis A travel vaccination program in Ontario, Canada

BACKGROUND

Hepatitis A virus (HAV) causes acute liver infection and is spread through the fecal-oral route. Travel to countries in HAV-endemic regions (e.g., Asia and Latin America) is a well-described risk factor for infection. Currently, Ontario publicly funds hepatitis A vaccination for some populations at high risk of HAV infection but not for all travellers to endemic countries. The objective of this study was to determine the cost-effectiveness of expanding publicly funded HAV vaccination to people planning travel to HAV-endemic regions, from the Ontario healthcare payer perspective.

METHODS

We conducted a cost-utility analysis comparing an expanded high-risk publicly-funded hepatitis A vaccination program including funded vaccine for travellers to endemic regions to the current high risk program in Ontario. A Markov state transition model was developed, including six possible health states. Model parameters were informed through targeted literature searches and included hepatitis A disease probabilities, utilities associated with health states, health system expenditures, and vaccine costs. Future costs and health outcomes were discounted at 1.5%. Primary outcomes included cost, incremental cost-effectiveness ratio (ICER) and quality adjusted life years (QALYs) over a lifetime time horizon. We conducted one-way, two-way, and probabilistic sensitivity analysis.

RESULTS

The expanded high risk HAV vaccine program provided few incremental health gains in the travel population (mean 0.000037 QALYs/person), at an incremental cost of $124.31. The ICER of the expanded program compared to status quo is $3,391,504/QALY gained. The conclusion of the model was robust to changes in key parameters across reasonable ranges.

CONCLUSIONS

The expanded vaccination program substantially exceeds commonly accepted cost-effectiveness thresholds. Further research concerning possible cost-effective implementation of high-risk travel hepatitis A vaccination should focus on a more integrated understanding of the risk of acquiring hepatitis A during travel to endemic regions (e.g., purpose, length of stay).

Hepatitis A seroprevalence in adolescents and young adults in Mexico: A 2012 National Health and Nutrition Survey analysis

To describe hepatitis A virus (HAV) seroprevalence and associated factors in adolescents (10-19 years) and young adults (20-25 years) in different Mexican regions, using 2012 National Health and Nutrition Survey data. A random selection of 1581 serum samples was analyzed. Weighted HAV seroprevalence with 95% confidence intervals (95%CI) and its association with sociodemographic factors were estimated. Mean weighted HAV seroprevalence was 69.3% (95%CI: 64.8-73.4) overall, with 58.8% (95%CI: 53.4-64.1) in adolescents and 83.0% (95%CI: 75.3-88.7) in young adults. By age of 10, 46.7% (95%CI: 33.9-60.0) were seropositive and by age of 15, 52.8% (95%CI: 36.5-68.5), corresponding to intermediate endemicity nationally. Factors associated with HAV seropositivity (adjusted odds ratio, aOR) included: lower socioeconomic status (SES) (aOR = 4.09 for low and aOR = 2.31 for medium versus high SES), older age (aOR = 0.29 for adolescents versus young adults), living in the South (aOR = 2.12 versus Central Mexico) or in rural areas (aOR = 2.25 versus urban areas). Regional differences and increased seroprevalence of HAV in marginalized populations present an important public health issue, as a relatively large proportion of young adults are susceptible to infection. The burden of symptomatic disease must be addressed further to support specific programs of continued sanitation and education improvement, and the possibility of vaccination in more susceptible regions.

Globalization and the Changing Epidemiology of Hepatitis A Virus

Increased economic interdependence, social integration, and other aspects of globalization are contributing to significant changes in hepatitis A epidemiology. Globally, the incidence of hepatitis A virus (HAV) infection is decreasing, the age at midpoint of population immunity (AMPI) is increasing, and the proportion of symptomatic cases is increasing as the average age at infection increases. In low-income countries, HAV remains endemic but improved water and sanitation systems are reducing transmission rates among young children. In high-income countries, most adults remain susceptible to HAV and foodborne outbreaks are becoming more frequent. Middle-income countries have diverse epidemiological profiles, and they play important roles in the global spread of HAV through international trade and travel. Future changes in the epidemiology of hepatitis A will be heavily influenced by globalization processes.

Type A viral hepatitis: A summary and update on the molecular virology, epidemiology, pathogenesis and prevention

Although epidemic jaundice was well known to physicians of antiquity, it is only in recent years that medical science has begun to unravel the origins of hepatitis A virus (HAV) and the unique pathobiology underlying acute hepatitis A in humans. Improvements in sanitation and the successful development of highly efficacious vaccines have markedly reduced the worldwide prevalence and incidence of this enterically-transmitted infection over the past quarter century, yet the virus persists in vulnerable populations and remains a common cause of food-borne disease outbreaks in economically-advantaged societies. Reductions in the prevalence of HAV have led to increases in the median age at which infection occurs, often resulting in more severe disease in affected persons and paradoxical increases in disease burden in some developing nations. Here, we summarize recent advances in the molecular virology of HAV, an atypical member of the Picornaviridae family, survey what is known of the pathogenesis of hepatitis A in humans and the host-pathogen interactions that typify the infection, and review medical and public health aspects of immunisation and disease prevention.

The impact of assumptions regarding vaccine-induced immunity on the public health and cost-effectiveness of hepatitis A vaccination: Is one dose sufficient?

Hepatitis A vaccination stimulates memory cells to produce an anamnestic response. In this study, we used a mathematical model to examine how long-term immune memory might convey additional protection against clinical/icteric infections. Dynamic and decision models were used to estimate the expected number of cases, and the costs and quality-adjusted life-years (QALYs), respectively. Several scenarios were explored by assuming: (1) varying duration of vaccine-induced immune memory, (2) and/or varying levels of vaccine-induced immune memory protection (IMP), (3) and/or varying levels of infectiousness in vaccinated individuals with IMP. The base case analysis assumed a time horizon of 25 y (2012 - 2036), with additional analyses over 50 and 75 y. The analyses were conducted in the Mexican public health system perspective. In the base case that assumed no vaccine-induced IMP, the 2-dose hepatitis A vaccination strategy was cost-effective compared with the 1-dose strategy over the 3 time horizons. However, it was not cost-effective if we assumed additional IMP durations of at least 10 y in the 25-y horizon. In the 50- and 75-y horizons, the 2-dose strategy was always cost-effective, except when 100% reduction in the probability of icteric Infections, 75% reduction in infectiousness, and mean durations of IMP of at least 50 y were assumed. This analysis indicates that routine vaccination of toddlers against hepatitis A virus would be cost-effective in Mexico using a single-dose vaccination strategy. However, the cost-effectiveness of a second dose depends on the assumptions of additional protection by IMP and the time horizon over which the analysis is performed.