Experiences, Enablers, and Challenges in Service Delivery and Integration of COVID-19 Vaccines: A Rapid Systematic Review.

The COVID-19 vaccination is a crucial public health intervention for controlling the spread and severity of the SARS-CoV2 virus. COVID-19 vaccines have been developed in record time, but their deployment has varied across countries, owing to differences in health system capacity, demand for the vaccine, and purchasing power of countries. The aim of this rapid review is to summarize and synthesize experiences on COVID-19 vaccine service delivery and integration to inform future COVID-19 vaccination programming and contribute to the knowledge base for future pandemic management. A systematic search was conducted in PubMed, Scopus, and Global Index Medicus databases. Twenty-five studies were included in the analysis. Included studies spanned nine countries where COVID-19 vaccines were delivered through mass, mobile, and fixed-post vaccination service delivery models. There was limited evidence of integrating COVID-19 vaccines into routine services for pregnant women, people who inject drugs, and leveraging existing health programs to deliver COVID-19 vaccines to the general population. Common challenges reported were vaccine skepticism, lack of adequate health workers, and linguistic barriers to access. Partnerships with a variety of stakeholders and the involvement of volunteers were vital in overcoming barriers and contributed to the efficient functioning of COVID-19 vaccination programs.

An integrated chance constraints approach for optimal vaccination strategies under uncertainty for COVID-19.

Despite concerted efforts by health authorities worldwide to contain COVID-19, the SARS-CoV-2 virus has continued to spread and mutate into new variants with uncertain transmission characteristics. Therefore, there is a need for new data-driven models for determining optimal vaccination strategies that adapt to the new variants with their uncertain transmission characteristics. Motivated by this challenge, we derive an integrated chance constraints stochastic programming (ICC-SP) approach for finding vaccination strategies for epidemics that incorporates population demographics for any region of the world, uncertain disease transmission and vaccine efficacy. An optimal vaccination strategy specifies the proportion of individuals in a given household-type to vaccinate to bring the reproduction number to below one. The ICC-SP approach provides a quantitative method that allows to bound the expected excess of the reproduction number above one by an acceptable amount according to the decision-maker's level of risk. This new methodology involves a multi-community household based epidemiology model that uses census demographics data, vaccination status, age-related heterogeneity in disease susceptibility and infectivity, virus variants, and vaccine efficacy. The new methodology was tested on real data for seven neighboring counties in the United States state of Texas. The results are promising and show, among other findings, that vaccination strategies for controlling an outbreak should prioritize vaccinating certain household sizes as well as age groups with relatively high combined susceptibility and infectivity.

Analysis of serological surveys of antibodies to SARS-CoV-2 in the United States to estimate parameters needed for transmission modeling and to evaluate and improve the accuracy of predictions.

Seroprevalence studies can estimate proportions of the population that have been infected or vaccinated, including infections that were not reported because of the lack of symptoms or testing. Based on information from studies in the United States from mid-summer 2020 through the end of 2021, we describe proportions of the population with antibodies to SARS-CoV-2 as functions of age and time. Slices through these surfaces at arbitrary times provide initial and target conditions for simulation modeling. They also provide the information needed to calculate age-specific forces of infection, attack rates, and - together with contact rates - age-specific probabilities of infection on contact between susceptible and infectious people. We modified the familiar Susceptible-Exposed-Infectious-Removed (SEIR) model to include features of the biology of COVID-19 that might affect transmission of SARS-CoV-2 and stratified by age and location. We consulted the primary literature or subject matter experts for contact rates and other parameter values. Using time-varying Oxford COVID-19 Government Response Tracker assessments of US state and DC efforts to mitigate the pandemic and compliance with non-pharmaceutical interventions (NPIs) from a YouGov survey fielded in the US during 2020, we estimate that the efficacy of social-distancing when possible and mask-wearing otherwise at reducing susceptibility or infectiousness was 31% during the fall of 2020. Initialized from seroprevalence among people having commercial laboratory tests for purposes other than SARS-CoV-2 infection assessments on 7 September 2020, our age- and location-stratified SEIR population model reproduces seroprevalence among members of the same population on 25 December 2020 quite well. Introducing vaccination mid-December 2020, first of healthcare and other essential workers, followed by older adults, people who were otherwise immunocompromised, and then progressively younger people, our metapopulation model reproduces seroprevalence among blood donors on 4 April 2021 less well, but we believe that the discrepancy is due to vaccinations being under-reported or blood donors being disproportionately vaccinated, if not both. As experimenting with reliable transmission models is the best way to assess the indirect effects of mitigation measures, we determined the impact of vaccination, conditional on NPIs. Results indicate that, during this period, vaccination substantially reduced infections, hospitalizations and deaths. This manuscript was submitted as part of a theme issue on "Modelling COVID-19 and Preparedness for Future Pandemics."

The heterogeneous mixing model of COVID-19 with interventions.

The emergence of mutant strains of COVID-19 reduces the effectiveness of vaccines in preventing infection, but remains effective in preventing severe illness and death. This paper established a heterogeneous mixing model of age groups with pharmaceutical and non-pharmaceutical interventions by analyzing the transmission mechanism of breakthrough infection caused by the heterogeneity of protection period under the action of vaccine-preventable infection with the original strain. The control reproduction number Rc of the system is analyzed, and the existence and stability of equilibrium are given by the comparison principle. Numerical simulation was conducted to evaluate the vaccination program and intervention measures in the customized scenario, demonstrating that the group-3 coverage rate p3 plays a key role in Rc. It is proposed that accelerating the rate of admission and testing is conducive to epidemic control by further fitting data of COVID-19 transmission in real scenarios. The findings provide a general modeling idea for the emergence of new vaccines to prevent infection by mutant strains, as well as a solid theoretical foundation for mainland China to formulate future vaccination strategies for new vaccines. This manuscript was submitted as part of a theme issue on "Modelling COVID-19 and Preparedness for Future Pandemics".

Mutation and SARS-CoV-2 strain competition under vaccination in a modified SIR model.

The crisis caused by the COVID-19 outbreak around the globe raised an increasing concern about the ongoing emergence of variants of the virus that may evade the immune response provided by vaccines. New variants appear due to mutation, and as the cases accumulate, the probability of the emergence of a variant of concern increases. In this article, we propose a modified susceptible, infected, and recovered (SIR) model with waning immunity that captures the competition of two strain classes of an infectious disease under the effect of vaccination with a highly contagious and deadly strain class emerging from a prior strain due to mutation. When these strains compete for a limited supply of susceptible individuals, changes in the efficiency of vaccines may affect the behaviour of the disease in a non-trivial way, resulting in complex outcomes. We characterise the parameter space including intrinsic parameters of the disease, and using the vaccine efficiencies as control variables. We find different types of transcritical bifurcations between endemic fixed points and a disease-free equilibrium and identify a region of strain competition where the two strain classes coexist during a transient period. We show that a strain can be extinguished either due to strain competition or vaccination, and we obtain the critical values of the efficiency of vaccines to eradicate the disease. Numerical studies using parameters estimated from publicly reported data agree with our theoretical results. Our mathematical model could be a tool to assess quantitatively the vaccination policies of competing and emerging strains using the dynamics in epidemics of infectious diseases.

Monitoring influenza vaccination coverage among healthcare workers during the COVID-19 pandemic: a three-year survey in a large university hospital in North-Western Italy.

Introduction: Healthcare workers (HCWs) are one of the highest priority groups recommended for seasonal influenza vaccination (SIV). Greater awareness of the importance of influenza vaccination was observed among HCWs after the start of the COVID-19 pandemic. The aim of this study was to analyze SIV coverage rates in the 2019-2020, 2020-2021 and 2021-2022 seasons among HCWs employed at the IRCCS Ospedale Policlinico San Martino in Genoa, in order to observe how coverage has changed since the COVID-19 pandemic began. Methods: A retrospective, single-center study was conducted among HCWs working at the IRCCS Ospedale Policlinico San Martino in Genoa. The vaccinated population was stratified by gender, age, qualification and area of activity, and the characteristics of vaccinated HCWs were analyzed. Results: While SIV coverage was below the recommended target in all seasons, a sharp increase was observed in 2020/2021 (12.8%; 40.9% and 23% in 2019/2020, 2020/2021 and 2021/2022, respectively). The mean and median age of vaccinees also increased during the 2020/2021 vaccination campaign (46.7 and 49 years, respectively) in comparison with the 2019/2020 season (43.5 and 45, respectively). In the 2019/2020 and 2021/2022 seasons, a higher proportion of vaccinees were physicians. Vaccinated females outnumbered males, but the coverage rate resulted greater in males than females in all three seasons. While a higher proportion of vaccinated subjects worked in medical areas, the most evident increase over the three years was seen among subjects working in the services area. Conclusions: This survey highlights the importance of studying the determinants that influence vaccination adherence and how the COVID-19 pandemic has affected SIV coverage.

Infectious Disease Spreading Fought by Multiple Vaccines Having a Prescribed Time Effect.

We propose a framework for the description of the effects of vaccinations on the spreading of an epidemic disease. Different vaccines can be dosed, each providing different immunization times and immunization levels. Differences due to individuals' ages are accounted for through the introduction of either a continuous age structure or a discrete set of age classes. Extensions to gender differences or to distinguish fragile individuals can also be considered. Within this setting, vaccination strategies can be simulated, tested and compared, as is explicitly described through numerical integrations.

Heterologous booster with inhaled adenovirus vector COVID-19 vaccine generated more neutralizing antibodies against different SARS-CoV-2 variants.

The rapid widespread Omicron subvariant BA.5 of SARS-CoV-2 has become a potential imminent pandemic threat, but available vaccines lack high efficacy against this subvariant. Thus, it is urgent to find highly protective vaccination strategies within available SARS-CoV-2 vaccines. Here, by using a SARS-CoV-2 pseudovirus neutralization assay, we demonstrated that the aerosol inhalation of adenoviral vector COVID-19 vaccine after two dose of inactivated vaccine (I-I-Ad5) led to higher levels of neutralizing antibodies against D614G strain (2041.00[95% CI, 1243.00-3351.00] vs 249.00[149.10-415.70]), Omicron BA.2 (467.10[231.00-944.40] vs 72.21[39.31-132.70]), BA.2.12.1(348.5[180.3-673.4] vs 53.17[31.29-90.37]), BA.2.13 (410.40[190.70-883.3] vs 48.48[27.87-84.32]), and BA.5 (442.40 vs 56.08[35.14-89.51]) than three inactivated vaccine doses (I-I-I). Additionally, the level of neutralizing antibodies against BA.5 induced by I-I-Ad5 was 2.41-fold higher than those boosted by a third dose of RBD subunit vaccine (I-I-S) (p = 0.1308). The conventional virus neutralizing assay confirmed that I-I-Ad5 induced higher titre of neutralizing antibodies than I-I-I (116.80[84.51-161.5] vs 4.40[4.00-4.83]). In addition, I-I-Ad5 induced higher, but later, anti-RBD IgG and IgA in plasma than I-I-I. Our study verified that mucosal immunization with aerosol inhalation of adenoviral vector COVID-19 vaccine may be an effective strategy to control the probable wave of BA.5 pandemic in addition to two inactivated vaccines.

CHASING HERD IMMUNITY: VACCINATION STRATEGIES OF RUSSIANS IN THE CONTEXT OF VARIOUS FORMS OF ENFORCEMENT TO VACCINATION

The focus of the analysis is the vaccination strategies of Russians highlighted on the basis of representations about the effectiveness of mass vaccination and the prospects for reaching the herd immunity, preferences to rely on individual or herd immunity, as well as the availability of vaccination or plans to be vaccinated. The vaccination strategies are regarded as individual decisions based on an assessment of the current situation and an interpretation of what herd immunity is and whether it is achievable. In this context, herd immunity is not just a coincidence but the result of largescale collective action. In the absence of a generally shared understanding of herd immunity and whether it is achievable, Russians prefer to rely on themselves and their health. By introducing various vaccination requirements and restrictions for the unvaccinated, the state is trying to act as a coordinator of collective action. However, an attempt to impose external demands is regarded by people as a form of enforcement of vaccination. Enforcement exerted on a single individual increases the chances of her/his vaccination but causes a repulsive effect among her/his circle of familiars. Based on data from an allRussian telephone survey (N=1503, conducted by the Foundation “Public Opinion”) and eight focus groups with supporters and opponents of vaccination from different cities of Russia, we show that various forms of enforcement of vaccination increase the risk of radicalization of relations between the state and society and also contribute to an even greater separation of individual and public interests. © 2022 Russian Public Opinion Research Center, VCIOM. All rights reserved.

COVID-19: Pathophysiology, Transmission, and Drug Development for Therapeutic Treatment and Vaccination Strategies.

COVID-19, a dreaded and highly contagious pandemic, is flagrantly known for its rapid prevalence across the world. Till date, none of the treatments are distinctly accessible for this life-threatening disease. Under the prevailing conditions of a medical emergency, one creative strategy for the identification of novel and potential antiviral agents gaining momentum in research institutions and progressively being leveraged by pharmaceutical companies is target-based drug repositioning/repurposing. Continuous monitoring and recording of results offer anticipation that this strategy may help to reveal new medications for viral infections. This review recapitulates the neoteric illation of COVID-19, its genomic dispensation, molecular evolution via phylogenetic assessment, drug targets, the most frequently worldwide used repurposed drugs and their therapeutic applications, and a recent update on vaccine management strategies. The available data from solidarity trials exposed that the treatment with several known drugs, viz. lopinavir-ritonavir, chloroquine, hydroxychloroquine, etc. had displayed various antagonistic effects along with no impactful result in the diminution of mortality rate. The drugs, like remdesivir, favipiravir, and ribavirin, have proved to be quite safer therapeutic options for treatment against COVID-19. Similarly, dexamethasone, convalescent plasma therapy and oral administration of 2DG are expected to reduce the mortality rate of COVID-19 patients.

HPV Vaccination during the COVID-19 Pandemic in Italy: Opportunity Loss or Incremental Cost.

OBJECTIVES: Italy was the first European country to introduce universal vaccination of adolescents, for both males and females, against Human Papilloma Virus (HPV) starting in 2017 with the NIP 2017-2019's release. However, vaccine coverage rates (VCRs) among adolescents have shown a precarious take-off since the NIP's release, and this situation worsened due to the impact of the COVID-19 pandemic in 2020. The aim of this work is to estimate the epidemiological and economic impact of drops in VCRs due to the pandemic on those generations that missed the vaccination appointment and to discuss alternative scenarios in light of the national data. METHODS: Through an analysis of the official ministerial HPV vaccination reports, a model was developed to estimate the number of 12-year-old males and females who were not vaccinated against HPV during the period 2017-2021. Based on previously published models that estimate the incidence and the economic impact of HPV-related diseases in Italy, a new model was developed to estimate the impact of the aggregated HPV VCRs achieved in Italy between 2017 and 2021. RESULTS: Overall, in 2021, 723,375 girls and 1,011,906 boys born between 2005 and 2009 were not vaccinated against HPV in Italy (42% and 52% of these cohorts, respectively). As compared with the 95% target provided by the Italian NIP, between 505,000 and 634,000 girls will not be protected against a large number of HPV-related diseases. For boys, the number of the unvaccinated population compared to the applicable target is over 615,000 in the 'best case scenario' and over 749,000 in the 'worst case scenario'. Overall, between 1.1 and 1.3 million young adolescents born between 2005 and 2009 will not be protected against HPV-related diseases over their lifetime with expected lifetime costs of non-vaccination that will be over EUR 905 million. If the 95% optimal VCRs were achieved, the model estimates a cost reduction equal to EUR 529 million, the net of the costs incurred to implement the vaccination program. CONCLUSION: Suboptimal vaccination coverage represents a missed opportunity, not only because of the increased burden of HPV-related diseases, but also in terms of economic loss. Thus, reaching national HPV immunization goals is a public health priority.

Vaccination strategies when vaccines are scarce: on conflicts between reducing the burden and avoiding the evolution of escape mutants.

When vaccine supply is limited but population immunization urgent, the allocation of the available doses needs to be carefully considered. One aspect of dose allocation is the time interval between the first and the second injections in two-dose vaccines. By stretching this interval, more individuals can be vaccinated with the first dose more quickly, which can be beneficial in reducing case numbers, provided a single dose is sufficiently effective. On the other hand, there has been concern that intermediate levels of immunity in partially vaccinated individuals may favour the evolution of vaccine escape mutants. In that case, a large fraction of half-vaccinated individuals would pose a risk-but only if they encounter the virus. This raises the question whether there is a conflict between reducing the burden and the risk of vaccine escape evolution or not. We develop an SIR-type model to assess the population-level effects of the timing of the second dose. Trade-offs can occur both if vaccine escape evolution is more likely or if it is less likely in half-vaccinated than in unvaccinated individuals. Their presence or absence depends on the efficacies for susceptibility and transmissibility elicited by a single dose.

COVID-19 Vaccination Strategies and Their Adaptation to the Emergence of SARS-CoV-2 Variants.

About one year after the identification of the first cases of pneumonia due to a novel coronavirus in Wuhan, several vaccines against SARS-CoV-2/COVID-19 started to be approved for emergency use or authorized for early or limited use. The rapid development of effective vaccines based on different technological platforms represents an unprecedented success for vaccinology, providing a unique opportunity for a successful public health intervention. However, it is widely known that only a limited number of vaccine doses are usually available at the beginning of vaccination campaigns against an emerging virus; in this phase, protecting health care workers and reducing mortality rates is the priority. When a larger number of vaccines become available, the identification of the drivers of virus circulation coupled with the use of transmission blocking vaccines are key to achieve epidemic control through population immunity. However, as we learned during the vaccination campaigns against the pandemic coronavirus, several factors may hamper this process. Thus, flexible plans are required to obtain the best sustainable result with available tools, modulating vaccination strategies in accordance with improved scientific knowledge, and taking into account the duration of protective immune response, virus evolution, and changing epidemic dynamics.

VACCINATION STRATEGIES THROUGH INTRA–COMPARTMENTAL DYNAMICS

We present a new epidemic model highlighting the roles of the immunization time and concurrent use of different vaccines in a vaccination campaign. To this aim, we introduce new intra-compartmental dynamics, a procedure that can be extended to various other situations, as detailed through specific case studies considered herein, where the dynamics within compartments are present and influence the whole evolution. © 2022, American Institute of Mathematical Sciences. All rights reserved.

A nonlinear optimal control method against the spreading of epidemics

To define a vaccination policy and antiviral treatment against the spreading of viral infections a nonlinear optimal (H-infinity) control approach is proposed. Actually, because of the scarcity of the resources for treating infectious diseases in terms of vaccines, antiviral drugs and other medical facilities, there is need to implement optimal control against the epidemics deployment. In this approach, the state-space model of the epidemics dynamics undergoes first approximate linearization around a temporary operating point which is recomputed at each time-step of the control method. The linearization is based on Taylor series expansion and on the computation of the associated Jacobian matrices. Next, an optimal (H-infinity) feedback controller is developed for the approximately linearized model of the epidemics. To compute the controller's feedback gains an algebraic Riccati equation is solved at each iteration of the control algorithm. Furthermore, the global asymptotic stability properties of the control scheme are proven through Lyapunov stability analysis. This paper's results confirm that optimal control of the infectious disease dynamics allows for eliminating its spreading while also keeping moderate the consumption of the related medication, that is vaccines and antiviral drugs.

COVID-19 Vaccination in Italian Children: The Limits of Parental Rights.

SARS-CoV-2 vaccination campaigns initially targeted the adult population. After the authorization of the main agencies, including the EMA (European Medicines Agency), the European Vaccination Plan now involves young people between the ages of 12-17 and 5-11. In assessing the child's "best interests", the refusal of vaccination by parents or guardians, in addition to the increased circulation of the virus, is responsible for the risk of social distancing. This reduction in social contacts, particularly during very sensitive ages such as adolescence, has been linked to the increased incidence of psychiatric illness, a significant reason for extending vaccination against SARS-CoV-2 in these younger children. One may consider that government should issue a law that allows the child to decide on the vaccination plan, even without the consent of the parents or guardians, without the need for a judge's ruling. The availability of the child should be the point of reference, according to the National Bioethics Committee, for consent to vaccination. The authors investigate the subject in depth in order to counteract vaccination hesitation, and promote the dissemination of correct scientific information, using every different possible communication tool, as well as social networks and schools.

Resources or trust: What matters more in the vaccination strategies of high-income liberal democracies?

Objectives: This paper presents an overview of the vaccination policy responses to the COVID-19 pandemic in Denmark, Canada, and the United States until September 1, 2021. The article seeks to understand the reasons for vaccination differences among high-income, liberal democracies. Methods: The country cases were selected based on tiers of population-level vaccination uptake within six months after vaccines became broadly available (for high-income countries). We conducted a rapid review of primary data for each country case. Through a graphical and descriptive analysis, we evaluated common patterns as well as significant divergences in the vaccination rollout across countries and its relationship with COVID-19 health outcomes, government policy responses, resource constraints, and socio-political factors. This inductive analysis provides a sense of how resource constraints compare with current political contexts in each country case that may influence the public's response to a national vaccination strategy. Results: Resources, socio-economic factors, and health outcomes related to COVID-19 do not ensure vaccination policy success as the case of the United States makes clear. Instead, trust in government and health systems appear to promise a higher vaccination uptake and maintained support for measures during a pandemic. Trust in government can be defined as the confidence citizens have that governmental actions will do what is right and perceived as fair. Conclusion: Denmark, the United States, and Canada are high-income liberal democracies with very different vaccine strategies and subsequently different vaccination outcomes across their populations. What appears to be critical to successful vaccination outcomes is high trust in government or health officials, along with the depoliticization of the COVID-19 pandemic among the country's political parties.

Effects of Vaccination Decisions and Peer influence on Epidemic Dynamics: A Network Perspective

Mathematical epidemiology models dealing with differential equation based compartmental techniques are very often successfully used to understand and predict epidemic dynamics. Simulation of these model dynamics on complex networks can reflect the spread of disease from person to person considering individual traits and takes into account of the heterogeneity in the disease spreading for more realistic aspect. In this paper, to understand effectiveness of different vaccination strategies, we form a SEIQR (susceptible-exposed-infected-quarantined-removed) model to analyze infection propagation of pandemics like COVID-19. We study how it is affected by various parameters and their physical meaning by using computational tools. Considering this model as the starting point, we study the effect of vaccination with a complex network model with six different subpopulations as susceptible, exposed, infected, quarantined, recovered and vaccinated. Different transition probabilities from one subpopulation to another is to be considered and severity of infection spread and vaccination coverage with different parameters is to be observed. Specifically, different types of vaccination strategies that could be chosen and their effect on final epidemic size has been explored. A computational study of vaccination effect on heterogeneous network is performed and results are interpreted in terms of physical significance. © 2021 IEEE.

COVID-19 epidemic in New York City: development of an age group-specific mathematical model to predict the outcome of various vaccination strategies.

BACKGROUND: Since December 14, 2020, New York City (NYC) has started the first batch of COVID-19 vaccines. However, the shortage of vaccines is currently an inevitable problem. Therefore, optimizing the age-specific COVID-19 vaccination is an important issue that needs to be addressed as a priority. OBJECTIVE: Combined with the reported COVID-19 data in NYC, this study aimed to construct a mathematical model with five age groups to estimate the impact of age-specific vaccination on reducing the prevalence of COVID-19. METHODS: We proposed an age-structured mathematical model and estimated the unknown parameters based on the method of Markov Chain Monte Carlo (MCMC). We also calibrated our model by using three different types of reported COVID-19 data in NYC. Moreover, we evaluated the reduced cumulative number of deaths and new infections with different vaccine allocation strategies. RESULTS: Compared with the current vaccination strategy in NYC, if we gradually increased the vaccination coverage rate for only one age groups from March 1, 2021 such that the vaccination coverage rate would reach to 40% by June 1, 2021, then as of June 1, 2021, the cumulative deaths in the 75-100 age group would be reduced the most, about 72 fewer deaths per increased 100,000 vaccinated individuals, and the cumulative new infections in the 0-17 age group would be reduced the most, about 21,591 fewer new infections per increased 100,000 vaccinated individuals. If we gradually increased the vaccination coverage rate for two age groups from March 1, 2021 such that the vaccination coverage rate would reach to 40% by June 1, 2021, then as of June 1, 2021, the cumulative deaths in the 65-100 age group would be reduced the most, about 36 fewer deaths per increased 100,000 vaccinated individuals, and the cumulative new infections in the 0-44 age group would be reduced the most, about 17,515 fewer new infections per increased 100,000 vaccinated individuals. In addition, if we had an additional 100,000 doses of vaccine for 0-17 and 75-100 age groups as of June 1, 2021, then the allocation of 80% to the 0-17 age group and 20% to the 75-100 age group would reduce the maximum numbers of new infections and deaths simultaneously in NYC. CONCLUSIONS: The COVID-19 burden including deaths and new infections would decrease with increasing vaccination coverage rate. Priority vaccination to the elderly and adolescents would minimize both deaths and new infections.