Simulation studies to assess the long-term effects of Japan's change from trivalent to quadrivalent influenza vaccination

Chronological trend of social contact patterns in Japan after the emergence of COVID-19

BACKGROUND

The social contact data for Japan as of 2022 showed a substantially decreased number of contacts compared with before the COVID-19 pandemic. However, it is unclear whether social contact continues to be depressed following the end of countermeasures against the pandemic. There is also scarce evidence regarding the influence of influenza-like illnesses (ILIs) on social contacts in Japan. Therefore, this study examined whether the reduction in contact frequency during the pandemic was temporary or persists today and assessed the impact of ILIs on social mixing patterns.

METHODS

We conducted online questionnaire surveys of individuals who experienced symptoms of ILIs periodically from 2022 to 2024 to compare the number of contacts per day during and after their illnesses. Contact matrices were obtained from the survey data. The impacts of the timing of the survey and the ILIs were examined using negative binomial regression analysis.

RESULTS

Contact patterns were generally age-assortative, and the average contact numbers gradually increased from March 2022 to June 2024. Most recently, the median number of contacts per day during illness was 3 (interquartile range [IQR] 2-7) and then rose to 4.5 (IQR 2-11) after recovery. The earlier survey and ILIs showed a negative association with the frequency of social contacts.

CONCLUSION

The frequency of social contacts in Japan tended to rise compared with that in 2021 but has not yet reached pre-pandemic levels. Individuals tended to decrease their contacts when they had symptoms caused by ILIs.

Prevalence of Influenza B/Yamagata Viruses From Season 2012/2013 to 2021/2022 in Italy as an Indication of a Potential Lineage Extinction

BACKGROUND

Influenza B/Yamagata viruses exhibited weak antigenic selection in recent years, reducing their prevalence over time and requiring no update of the vaccine component since 2015. To date, no B/Yamagata viruses have been isolated or sequenced since March 2020.

METHODS

The antibody prevalence against the current B/Yamagata vaccine strain in Italy was investigated: For each influenza season from 2012/2013 to 2021/2022, 100 human serum samples were tested by haemagglutination inhibition (HAI) assay against the vaccine strain B/Phuket/3073/2013. In addition, the sequences of 156 B/Yamagata strains isolated during the influenza surveillance activities were selected for analysis of the haemagglutinin genome segment.

RESULTS

About 61.9% of the human samples showed HAI antibodies, and 21.7% had protective antibody levels. The prevalence of antibodies at protective levels in the seasons between the isolation of the strain and its inclusion in the vaccine was between 11% and 25%, with no significant changes observed in subsequent years. A significant increase was observed in the 2020/2021 season, in line with the increase in influenza vaccine uptake during the pandemic. Sequence analysis showed that from 2014/2015 season onward, all B/Yamagata strains circulating in Italy were closely related to the B/Phuket/2013 vaccine strain, showing only limited amino acid variation.

CONCLUSIONS

A consistent prevalence of antibodies to the current B/Yamagata vaccine strain in the general population was observed. The prolonged use of a well-matched influenza vaccine and a low antigenic diversity of B/Yamagata viruses may have facilitated a strong reduction in B/Yamagata circulation, potentially contributing to the disappearance of this lineage.

Imprecision in vaccine adverse event reporting and a methodological analysis of reporting systems to improve pharmacovigilance and public health

INTRODUCTION

This study documents imprecision in Japanese reports of adverse events following immunization (AEFI). In doing so, it presents methods to analyze this imprecision.

METHODS

These methods include use of unique Japanese data on the validity of certain AEFIs. They also include ways to estimate AEFI rates, which allow comparison of AEFI data between countries. Using US AEFI data for comparison, we show how differences in AEFI reporting systems likely influence AEFI statistics.

RESULTS

Although our comparisons of AEFI rates are not precise, many of the difference we detected between Japanese and US statistics make sense and reflect differences in the societal and medical perspectives on various vaccines or can be explained by differences in the reporting systems including reporting sources. For example, differences in societal and medical perspective probably underly the extraordinarily high Japanese rates of anaphylaxis and other AEs following HPV immunizations from 2010 to 2016 compared to US rates and to Japanese rates for other vaccines. High US rates of reported Guillain-Barré syndrome following influenza vaccination relative to Japanese rates and to rates for other US vaccines are consistent with data suggesting that the index of suspicion for such reactions could affect AEFI rates. The findings that over half of Japanese anaphylaxis reports for every vaccine are erroneous, and that close to half of "serious" Japanese AEFI cases probably are not serious may be due in part not only to explanations unique to Japan, but also to factors that apply to the USA and other countries. Differences in reporting systems account for a much higher rate of non-serious AEFI reports in the USA compared to Japan. Japanese marketing authorization holders are probably at least as assiduous and timely in their reporting of AEFIs as health care providers, though granular level differences are apparent in reporting by various sources.

CONCLUSION

The methods we used to analyze the validity of Japanese statistics can be used to analyze the validity of AEFI reports from other countries and aid the harmonization of adverse event reporting systems. Eventually, similar reporting systems might be adapted for drugs and medical devices.

The estimated disease burden of COVID-19 in Japan from 2020 to 2021

BACKGROUND

To date, it is not fully understood to what extent COVID-19 has burdened society in Japan. This study aimed to estimate the total disease burden due to COVID-19 in Japan during 2020-2021.

METHODS

We stratify disease burden estimates by age group and present it as absolute Quality Adjusted Life Years (QALYs) lost and QALYs lost per 100,000 persons. The total estimated value of QALYs lost consists of (1) QALYs lost brought by deaths due to COVID-19, (2) QALYs lost brought by inpatient cases, (3) QALYs lost brought by outpatient cases, and (4) QALYs lost brought by long-COVID.

RESULTS

The total QALYs lost due to COVID-19 was estimated as 286,782 for two years, 114.0 QALYs per 100,000 population per year. 71.3% of them were explained by the burden derived from deaths. Probabilistic sensitivity analysis showed that the burden of outpatient cases was the most sensitive factor.

CONCLUSIONS

The large part of disease burden due to COVID-19 in Japan from the beginning of 2020 to the end of 2021 was derived from Wave 3, 4, and 5 and the proportion of QALYs lost due to morbidity in the total burden increased gradually. The estimated disease burden was smaller than that in other high-income countries. It will be our future challenge to take other indirect factors into consideration.

Comparisons in the Health and Economic Assessments of Using Quadrivalent Versus Trivalent Influenza Vaccines: A Systematic Literature Review

OBJECTIVES

Seasonal influenza vaccines protect against 3 (trivalent influenza vaccine [IIV3]) or 4 (quadrivalent influenza vaccine [IIV4]) viruses. IIV4 costs more than IIV3, and there is a trade-off between incremental cost and protection. This is especially the case in low- and middle-income countries (LMICs) with limited budgets; previous reviews have not identified studies of IIV4-IIV3 comparisons in LMICs. We summarized the literature that compared health and economic outcomes of IIV4 and IIV3, focused on LMICs.

METHODS

We systematically searched 5 databases for articles published before October 6, 2021, that modeled health or economic effects of IIV4 versus IIV3. We abstracted data and compared findings among countries and models.

RESULTS

Thirty-eight studies fit our selection criteria; 10 included LMICs. Most studies (N = 31) reported that IIV4 was cost-saving or cost-effective compared with IIV3; we observed no difference in health or economic outcomes between LMICs and other countries. Based on cost differences of influenza vaccines, only one study compared coverage of IIV3 with IIV4 and reported that the maximum IIV4 price that would still yield greater public health impact than IIV3 was 13% to 22% higher than IIV3.

CONCLUSIONS

When vaccination coverage with IIV4 and IIV3 is the same, IIV4 tends to be not only more effective but more cost-effective than IIV3, even with relatively high price differences between vaccine types. Alternatively, where funding is limited as in most LMICs, higher vaccine coverage can be achieved with IIV3 than IIV4, which could result in more favorable health and economic outcomes.

Switching from trivalent to quadrivalent inactivated influenza vaccines in Uruguay: a cost-effectiveness analysis

We evaluated the cost-utility of replacing trivalent influenza vaccine (TIV) with quadrivalent influenza vaccine (QIV) in the current target populations in Uruguay. An existing decision-analytic static cost-effectiveness model was adapted for Uruguay. The population was stratified into age groups. Costs and outcomes were estimated for an average influenza season, based on observed rates from 2013 to 2019 inclusive. Introducing QIV instead of TIV in Uruguay would avoid around 740 additional influenza cases, 500 GP consultations, 15 hospitalizations, and three deaths, and save around 300 workdays, for the same vaccination coverage during an average influenza season. Most of the influenza-related consultations and hospitalizations would be avoided among children ≤4 and adults ≥65 years of age. Using QIV rather than TIV would cost an additional ~US$729,000, but this would be partially offset by savings in consultations and hospitalization costs. The incremental cost per quality-adjusted life-year (QALY) gained with QIV would be in the order of US$18,000 for both the payor and societal perspectives, for all age groups, and around US$12,000 for adults ≥65 years of age. The main drivers influencing the incremental cost-effectiveness ratio were the vaccine efficacy against the B strains and the percentage of match each season with the B strain included in TIV. Probabilistic sensitivity analysis showed that switching to QIV would provide a favorable cost-utility ratio for 50% of simulations at a willingness-to-pay per QALY of US$20,000. A switch to QIV is expected to be cost-effective for the current target populations in Uruguay, particularly for older adults.

Epidemiology and burden of illness of seasonal influenza among the elderly in Japan: A systematic literature review and vaccine effectiveness meta-analysis

BACKGROUND

Elderly populations are particularly vulnerable to influenza and often require extensive clinical support. In Japan, nationwide passive surveillance monitors seasonal influenza but does not capture the full disease burden. We synthesized existing evidence on the epidemiology, vaccine effectiveness (VE), and economic burden of seasonal influenza in the elderly population.

METHODS

PubMed, EMBASE, and ICHUSHI were searched for articles on seasonal influenza in Japan, published between 1997 and 2018, in English or Japanese. Grey literature was also assessed. A random-effects meta-analysis characterized VE of influenza vaccines among studies reporting this information.

RESULTS

Of 1,147 identified articles, 143 met inclusion criteria. Reported incidence rates varied considerably depending on study design, season, study setting and, most importantly, case definition. In nursing homes, the maximum reported attack rate was 55.2% and in the 16 articles reporting mortality rates, case fatality rates varied from 0.009% to 14.3%. Most hospitalizations were in people aged >60; healthcare costs were partially mitigated by vaccine administration. Meta-analysis estimated overall VE of 19.1% (95% CI: 2.3% - 33.0%) with a high proportion of heterogeneity (I2 : 89.1%). There was a trend of lower VE in older people (40.1% [-57.3-77.2] in the <65 group; 12.9% [-8.0-29.8] in those 65; P = .21).

CONCLUSIONS

Despite differences between studies that make comparisons challenging, the influenza burden in elderly Japanese is significant. While vaccines are effective, current vaccination programs offer suboptimal protection. Health economic data and cost-effectiveness analyses were limited and represent areas for policy-relevant future research.

Cost-Effectiveness of Quadrivalent Versus Trivalent Influenza Vaccination in the Dutch National Influenza Prevention Program

OBJECTIVES

As of 2019, quadrivalent influenza vaccine (QIV) has replaced trivalent influenza vaccine (TIV) in the national immunization program in The Netherlands. Target groups are individuals of 60+ years of age and those with chronic diseases. The objective was to estimate the incremental break-even price of QIV over TIV at a threshold of €20 000 per quality-adjusted life-year (QALY).

METHODS

An age-structured compartmental dynamic model was adapted for The Netherlands to assess health outcomes and associated costs of vaccinating all individuals at higher risk for influenza with QIV instead of TIV over the seasons 2010 to 2018. Influenza incidence rates were derived from a global database. Other parameters (probabilities, QALYs and costs) were extracted from the literature and applied according to Dutch guidelines. A threshold of €20 000 per QALY was applied to estimate the incremental break-even prices of QIV versus TIV. Sensitivity analyses were performed to test the robustness of the model outcomes.

RESULTS

Retrospectively, vaccination with QIV instead of TIV could have prevented on average 9500 symptomatic influenza cases, 2130 outpatient visits, 84 hospitalizations, and 38 deaths per year over the seasons 2010 to 2018. This translates into 385 QALYs and 398 life-years potentially gained. On average, totals of €431 527 direct and €2 388 810 indirect costs could have been saved each year.

CONCLUSION

Using QIV over TIV during the influenza seasons 2010 to 2018 would have been cost-effective at an incremental price of maximally €3.81 (95% confidence interval, €3.26-4.31). Sensitivity analysis showed consistent findings on the incremental break-even price in the same range.

Costs and benefits of interventions aimed at major infectious disease threats: lessons from the literature

Pandemics and major outbreaks have the potential to cause large health losses and major economic costs. To prioritize between preventive and responsive interventions, it is important to understand the costs and health losses interventions may prevent. We review the literature, investigating the type of studies performed, the costs and benefits included, and the methods employed against perceived major outbreak threats. We searched PubMed and SCOPUS for studies concerning the outbreaks of SARS in 2003, H5N1 in 2003, H1N1 in 2009, Cholera in Haiti in 2010, MERS-CoV in 2013, H7N9 in 2013, and Ebola in West-Africa in 2014. We screened titles and abstracts of papers, and subsequently examined remaining full-text papers. Data were extracted according to a pre-constructed protocol. We included 34 studies of which the majority evaluated interventions related to the H1N1 outbreak in a high-income setting. Most interventions concerned pharmaceuticals. Included costs and benefits, as well as the methods applied, varied substantially between studies. Most studies used a short time horizon and did not include future costs and benefits. We found substantial variation in the included elements and methods used. Policymakers need to be aware of this and the bias toward high-income countries and pharmaceutical interventions, which hampers generalizability. More standardization of included elements, methodology, and reporting would improve economic evaluations and their usefulness for policy.

Optimising age coverage of seasonal influenza vaccination in England: A mathematical and health economic evaluation

For infectious disease prevention, policy-makers are typically required to base policy decisions in light of operational and monetary restrictions, prohibiting implementation of all candidate interventions. To inform the evidence-base underpinning policy decision making, mathematical and health economic modelling can be a valuable constituent.

Applied to England, this study aims to identify the optimal target age groups when extending a seasonal influenza vaccination programme of at-risk individuals to those individuals at low risk of developing complications following infection. To perform this analysis, we utilise an age- and strain-structured transmission model that includes immunity propagation mechanisms which link prior season epidemiological outcomes to immunity at the beginning of the following season. Making use of surveillance data from the past decade in conjunction with our dynamic model, we simulate transmission dynamics of seasonal influenza in England from 2012 to 2018. We infer that modified susceptibility due to natural infection in the previous influenza season is the only immunity propagation mechanism to deliver a non-negligible impact on the transmission dynamics. Further, we discerned case ascertainment to be higher for young infants compared to adults under 65 years old, and uncovered a decrease in case ascertainment as age increased from 65 to 85 years of age.

Our health economic appraisal sweeps vaccination age space to determine threshold vaccine dose prices achieving cost-effectiveness under differing paired strategies. In particular, we model offering vaccination to all those low-risk individuals younger than a given age (but no younger than two years old) and all low-risk individuals older than a given age, while maintaining vaccination of at-risk individuals of any age. All posited strategies were deemed cost-effective. In general, the addition of low-risk vaccination programmes whose coverage encompassed children and young adults (aged 20 and below) were highly cost-effective. The inclusion of elder age-groups to the low-risk programme typically lessened the cost-effectiveness. Notably, elderly-centric programmes vaccinating from 65-75 years and above had the least permitted expense per vaccine.

Vaccination is an established method to provide protection against seasonal influenza and its complications. Yet, a need to administer an updated vaccine on an annual basis presents significant operational challenges and sizeable costs. Consequently, policy makers typically have to decide how to deploy a finite amount of resource in a cost-effective manner. A combination of mathematical and health economic modelling can be used to address such a question. Here, we developed an age- and strain-structured mathematical model for seasonal influenza transmission dynamics that incorporates mechanisms for immunity propagation, which we used to reconstruct transmission dynamics of seasonal influenza in England from 2012 to 2018.

We then performed a health economic evaluation assessing the cost-effectiveness of extending a seasonal influenza vaccination programme of at-risk individuals to also include, for targeted age groups, those individuals at low risk of developing complications following infection. The findings suggest the inclusion of low-risk vaccination programmes whose coverage encompassed children and young adults (aged 20 and below) to be highly cost-effective. In contrast, the inclusion of elder age-groups to the low-risk programme typically lessened the cost-effectiveness.

Interim 2019/2020 Influenza Vaccine Effectiveness in Japan from October 2019 to January 2020

Herein, we report the interim vaccine effectiveness (VE) of a quadrivalent inactivated influenza vaccine, during the 2019/2020 influenza season, in Japan. We conducted a retrospective observational cohort study of 381 patients aged ≥15 years, who were enrolled with influenza like illnesses and examined via the rapid influenza diagnostic test, at the Ambulatory Care unit of the National Center for Global Health and Medicine in Tokyo, Japan, from the beginning of October 2019 to the end of January 2020. VE was estimated using a test-negative design. VE was calculated as (1 - odds ratio) × 100%, comparing influenza A test positivity between vaccinated and unvaccinated patients. Of the 381 patients initially screened for inclusion, 314 were enrolled in the study. Of these, 105 were vaccinated, 98 were diagnosed with influenza A, and 5 were diagnosed with influenza B. Overall VE against influenza A was 27.6% (95% confidence interval [CI], ‒21.1 to +57.4), and in patients aged ≥65 years, it was 47.3% (95% CI, ‒76.0 to +86.0). This indicates that the influenza vaccination offered continued protection during the 2019/2020 influenza season, but a detailed analysis of more cases with a careful consideration of methodology is necessary to estimate VE more precisely.

The characteristics of influenza-like illness management in Japan

Background

This study aimed to make a quantitative assessment of the management of influenza-like illnesses (ILI) in Japanese healthcare settings.

Methods

We analysed participants’ healthcare-seeking behaviour and physicians’ practice in January 2019 using an online survey of 200 households in Japan. Quality of life score, quality-adjusted life years lost, the duration of symptoms, and the duration of absence from work were compared between the influenza ILI group and the non-influenza ILI group with one-to-one propensity score matching. Missing data were imputed using multiple imputation.

Results

In total, 261 of the 600 (43.5%) participants had at least one episode of influenza-like illness during January 2019. Of these, 194 (75.5%) visited healthcare facilities, 167 (86.1%) within 2 days of onset of symptoms. A total of 169 out of 191 (88.5%) received a rapid influenza diagnostic test and 101 were diagnosed with influenza, of whom 95.0% were treated with antivirals. The median quality-adjusted life-years (QALYs) lost was 0.0055 (interquartile range, IQR 0.0040–0.0072) and median absence from work for a single episode of influenza-like illness was 2 days (IQR 1–5 days). Albeit QALYs lost per episode was not different between two groups, the influenza ILI group showed longer duration of absence from work (5 days, IQR 4–6 days) than the non-influenza ILI group (2 days, IQR 1–3 days).

Conclusions

In Japan, most people with influenza-like illnesses visit healthcare facilities soon after symptoms first occur and receive a diagnostic test. Those with influenza are usually treated with antivirals. Absence from work was longer for influenza than other similar illnesses.

Immunogenicity and safety of high-dose quadrivalent influenza vaccine in Japanese adults ≥65 years of age: a randomized controlled clinical trial

A trivalent high-dose inactivated influenza vaccine has been licensed in healthy adults ≥65 years of age and provides better protection against influenza infection and related complications than trivalent standard-dose vaccine. This phase I/II clinical trial (NCT03233217), conducted at two sites in Japan, examined the safety and immunogenicity of a quadrivalent formulation of the high-dose inactivated influenza vaccine (IIV4-HD). Healthy adults ≥65 years of age were randomized to receive IIV4-HD by intramuscular injection (n = 60), IIV4-HD by subcutaneous injection (n = 60), or a quadrivalent standard-dose inactivated influenza vaccine (IIV4-SD) by subcutaneous injection (n = 55). Irrespective of administration route, post-vaccination (day 28–35) hemagglutination inhibition geometric mean titers and seroconversion rates were higher for IIV4-HD than for IIV4-SD. Hemagglutination inhibition geometric mean titers and seroconversion rates were also higher for intramuscular than subcutaneous administration of IIV4-HD. Solicited reactions were more common in participants who received IIV4-HD administered subcutaneously than in those who received IIV4-HD administered intramuscularly or IIV4-SD administered subcutaneously. Unsolicited adverse events were similar between the vaccine groups, and no safety signals were detected. This study showed that IIV4-HD administered by either intramuscular or subcutaneous injection was well tolerated and highly immunogenic in healthy Japanese adults ≥65 years of age. Although this study was descriptive, the results add to the evidence that high-dose inactivated influenza vaccines are more immunogenic than standard-dose vaccines in this age group and that intramuscular administration provides greater immunogenicity and lower reactogenicity than subcutaneous administration.

Interplay between cost and effectiveness in influenza vaccine uptake: a vaccination game approach

Pre-emptive vaccination is regarded as one of the most protective measures to control influenza outbreak. There are mainly two types of influenza viruses-influenza A and B with several subtypes-that are commonly found to circulate among humans. The traditional trivalent (TIV) flu vaccine targets two strains of influenza A and one strain of influenza B. The quadrivalent (QIV) vaccine targets one extra B virus strain that ensures better protection against influenza; however, the use of QIV vaccine can be costly, hence impose an extra financial burden to society. This scenario might create a dilemma in choosing vaccine types at the individual level. This article endeavours to explain such a dilemma through the framework of a vaccination game, where individuals can opt for one of the three options: choose either of QIV or TIV vaccine or none. Our approach presumes a mean-field framework of a vaccination game in an infinite and well-mixed population, entangling the disease spreading process of influenza with the coevolution of two types of vaccination decision-making processes taking place before an epidemic season. We conduct a series of numerical simulations as an attempt to illustrate different scenarios. The framework has been validated by the so-called multi-agent simulation (MAS) approach.

Cost-effectiveness of quadrivalent versus trivalent influenza vaccine for elderly population in China

BACKGROUND

Influenza-associated excess death occurred most in the elderly. We aimed to assess the cost-effectiveness of quadrivalent influenza vaccine (QIV) versus trivalent influenza vaccine (TIV) for prevention of influenza infection among elderly population in China.

METHODS

A decision-analytic model was developed to compare 1-year clinical and economic outcomes of three influenza vaccination options (no vaccination, TIV, and QIV) in a hypothetical cohort of Chinese elderly aged 69 years. Outcome measures included cost, influenza infection rate, influenza-related mortality rate, quality-adjusted life-years (QALY) loss, and incremental cost-effectiveness ratio (ICER) from societal perspective. Sensitivity analyses were performed to examine the uncertainty of model inputs.

RESULTS

Base-case results showed no vaccination was dominated (more costly at higher QALY loss) by TIV and QIV. QIV was more costly (USD56.29 versus USD54.28) with lower influenza infection rate (0.608 versus 0.623), mortality rate (0.00199 versus 0.00204), and QALY loss (0.01213 versus 0.01243) than TIV. QIV was cost-effective compared to TIV with ICER of 6,700 USD/QALY below the willingness-to-pay threshold (29,580 USD/QALY). One-way sensitivity analysis found the cost-effectiveness of QIV was subject to the relative risk of vaccine effectiveness of QIV versus TIV, and TIV would be cost-effective if the relative risk was below 1.05. In 10,000 Monte Carlo simulations, the probabilities of QIV, TIV, and no vaccination to be cost-effective were 86.3%, 13.7%, and 0%, respectively.

CONCLUSION

QIV appears to be a cost-effective option compared to TIV and no influenza vaccination for elderly population in China.

Modelling the optimal target age group for seasonal influenza vaccination in Japan

BACKGROUND

In Japan, the current influenza vaccination programme is targeting older individuals. On the other hand, epidemics of influenza are likely to be mainly driven by children. In this study, we consider the most cost-effective target age group for a seasonal influenza vaccination programme in Japan.

METHODS

We constructed a deterministic compartmental Susceptible-Exposed-Infectious-Recovered (SEIR) model with data from the 2012/13 to 2014/15 influenza seasons in Japan. Bayesian inference with Markov Chain Monte Carlo method was used for parameter estimation. Cost-effectiveness analyses were conducted from public health care payer's perspective.

RESULTS

A scenario targeting children under 15 was expected to reduce the number of cases 6,382,345 compared to the current strategy. A scenario targeting elderly population (age over 49 years) was expected to reduce the number of cases 693,206. The children targeted scenario demonstrated negative ICER (incremental cost-effectiveness ratio) value. On the other hand, elderly targeted scenario demonstrated higher ICER value than the willingness to pay (50,000 USD/QALY).

CONCLUSIONS

A vaccination programme which targets children under 15 is predicted to have much larger epidemiological impact than those targeting elderly.

Quadrivalent versus trivalent influenza vaccine: clinical outcomes in two influenza seasons, historical cohort study

OBJECTIVES

The quadrivalent influenza vaccine (QIV) contains two influenza B antigens (one of each B lineage), while the trivalent vaccine (TIV) contains solely one. As a result, a mismatch between the circulating B lineage and the lineage in the TIV occurs frequently. We aimed to compare the frequency of clinically significant outcomes in a large cohort of vaccinees receiving either TIV or QIV.

METHODS

Historical cohort study of all inactivated influenza vaccinees (aged 3 years and older) in a Health Maintenance Organization insuring 1.2 million individuals, over two influenza seasons in which both vaccines were provided non-selectively. Primary outcome was hospital admissions during the influenza season. Multivariate analysis was performed using logistic regression to adjust for relevant covariates.

RESULTS

Our cohort included 150 518 and 168 296 vaccinees in the first (S1) and second season (S2), respectively. The two influenza seasons were characterized by high Influenza B activity. Of those vaccinated with QIV, 2074 of 49 726 (4.2%) and 6563 of 121 741 (5.4%) were hospitalized compared with 7378 of 100 792 (7.3%) and 3372 of 46 555 (7.2%) of those vaccinated with TIV (S1 and S2, respectively). After multivariate analysis adjusting for several covariates (gender, age, socioeconomic status, chronic morbidity, timing of vaccination), compared with TIV recipients, QIV vaccinees had lower odds for hospitalization (OR = 0.92, 95% CI 0.87-0.98 and OR = 0.89, 95% CI 0.85-0.93) or emergency department visit (OR = 0.91, 95% CI 0.87-0.95 and OR = 0.84, 95% CI 0.81-0.87) in S1 and S2, respectively (p < 0.001). Lower odds of mortality and influenza-like illness were also observed in S2 (OR = 0.61, 95% CI 0.50-0.75 and OR = 0.92, 95% CI 0.90-0.95, respectively).

CONCLUSIONS

In seasons with relatively high influenza B activity, QIV appeared more protective than TIV in Israel.

Economic consequences of Japanese schools' recovery certificate policy for seasonal influenza

Background

Like other countries, Japan experiences a seasonal influenza epidemic every year. In order to return to school after a influenza-related absence, most Japanese students are required to submit a recovery certificate (chiyu-shoumeisyo in Japanese). The objective of this study was to estimate the economic consequences of this practice.

Methods

A cost analysis was conducted to estimate the additional costs incurred by the issuance of recovery certificates from a restricted societal perspective. The estimated number of influenza patients under 15 years old from the 2013/14 season to the 2017/18 season, the proportion of working mothers were used to calculate the estimated total number of recovery certificates issued per year. The cost of return visits to physicians and the cost for issuing certificates were included in the direct costs. Productivity loss was estimated using the mean monthly salary of women and was included in indirect costs.

Results

The recovery certificate policy imposed an additional cost of 0.94 million USD per one million population. One-way deterministic sensitivity analysis demonstrated that the additional cost of the recovery certificate policy amounted to between 0.55 and 2.27 million USD per one million population. Probabilistic sensitivity analysis showed similar results.

Conclusions

The recovery certificate policy has a substantial negative economic impact on the Japanese healthcare system and society from a restricted societal perspective.

Sustainable vaccine development: a vaccine manufacturer's perspective

Vaccination remains the most cost-effective public health intervention after clean water, and the benefits impressively outweigh the costs. The efforts needed to fulfill the steadily growing demands for next-generation and novel vaccines designed for emerging pathogens and new indications are only realizable in a sustainable business model. Vaccine development can be fast-tracked through strengthening international collaborations, and the continuous innovation of technologies to accelerate their design, development, and manufacturing. However, these processes should be supported by a balanced project portfolio, and by managing sustainable vaccine procurement strategies for different types of markets. Collectively this will allow a gradual shift to a more streamlined and profitable vaccine production, which can significantly contribute to the worldwide effort to shape global health.