Barriers and activities to implementing or expanding influenza vaccination programs in low- and middle-income countries: A global survey

Maintaining Immunizations for Vaccine-Preventable Diseases in a Changing World

Immunization has saved an estimated 154 million lives over the past 50 years since the launch of the Essential (formerly Expanded) Program on Immunization in 1974, representing 6 lives saved every minute, every year, for 50 years. But achieving and maintaining high immunization coverage have required sustained political and public commitment, financial resources, strong partnerships, research and innovation, and communication and advocacy. New and evolving challenges to maintaining high immunization coverage have emerged alongside long-standing stubborn obstacles. We review some of these key challenges to immunization in this dynamic, changing world and summarize some promising solutions. Success in some regions of the world in eliminating polio, measles, and rubella, and reducing morbidity and mortality from other vaccine-preventable diseases, should provide hope that progress can be made in achieving and maintaining high immunization coverage. We cannot afford to do otherwise.

Advancing influenza vaccines: A review of next-generation candidates and their potential for global health impact

BACKGROUND

Influenza vaccines are an essential tool for influenza prevention, control and preparedness. However, demand for them and their programmatic suitability globally is significantly influenced by their variable effectiveness against influenza illness annually, limited duration of protection and need for yearly updating and vaccination. As such, the World Health Organization and major funders, such as the United States National Institute of Allergy and Infectious Diseases and Bill and Melinda Gates Foundation, have strongly encouraged developing influenza vaccines with increased efficacy, breadth and duration of protection. Here, we review the next-generation influenza vaccine pipeline, focusing on products in clinical development, and compare their characteristics to currently approved seasonal influenza vaccines.

METHODS

To identify and characterize next-generation influenza vaccine candidates, we conducted a comprehensive literature review, using the CIDRAP Universal Influenza Vaccine Technology Landscape as a primary reference source and extracting additional information from peer-reviewed manuscripts, clinical trial records and other media in the public domain.

RESULTS

Our analysis reveals a robust clinical development pipeline for next-generation influenza vaccines, featuring a diversity of approaches to address existing vaccine challenges and several candidates in advanced stages of development. mRNA vaccines emerged as a predominant platform, as evidenced by the number of candidates focused on improved seasonal protection as well as combination vaccine candidates targeting additional respiratory viruses.

CONCLUSION

While still early in development, results from universal or broadly protective products are promising and warrant continued investment from funders. As most Phase 3 candidates are mRNA-based and include combination vaccines, it is critical to begin considering how these new products may become integrated into the current global influenza vaccine strain selection and manufacturing ecosystems, and existing immunization programmes.

IAPSM's Position Paper on Influenza Vaccines for Adult Immunization in India

Influenza causes significant morbidity, hospitalizations, and mortality due to lower respiratory tract infections in India. This paper reviews the current evidence regarding influenza epidemiology, the need for vaccination, immunogenicity, and efficacy of available vaccines and provides recommendations for influenza vaccination for adults by the Indian Association of Preventive and Social Medicine (IAPSM). The risk group among adults includes people with chronic disease, the elderly, immunocompromised individuals, pregnant women, travelers, and healthcare workers. Influenza activity is affected by seasons, humidity, and latitude, leading to variability in influenza peaks in different regions of India. The most effective preventive intervention against influenza is vaccination. Current influenza vaccines have good safety profiles, vaccine efficacy, and acceptable cost-effectiveness. As the virus mutates, the vaccine composition should follow WHO recommendations for the current influenza season. Introducing readily available, conventional, and less expensive trivalent influenza vaccines under the national program can achieve maximum impact on the adult population and potentially prevent future outbreaks and pandemics. IAPSM recommends considering routine use of IIV for all individuals above 60 years, adults with comorbidities, and pregnant women in India. The program managers should consider the pattern of influenza seasonality in a particular region. Influenza surveillance conducted through a structured network of laboratories in India has the potential to provide information about circulating strains, morbidity, and mortality. IAPSM emphasizes conducting community-based studies regarding influenza's burden, vaccine efficacy, timing of vaccination, and cost-effectiveness among Indian adults to generate evidence.

Costs of seasonal influenza vaccine delivery in a pediatric demonstration project for children aged 6-23 months - Nakuru and Mombasa Counties, Kenya, 2019-2021

BACKGROUND

During November 2019-October 2021, a pediatric influenza vaccination demonstration project was conducted in four sub-counties in Kenya. The demonstration piloted two different delivery strategies: year-round vaccination and a four-month vaccination campaign. Our objective was to compare the costs of both delivery strategies.

METHODS

Cost data were collected using standardized questionnaires and extracted from government and project accounting records. We reported total costs and costs per vaccine dose administered by delivery strategy from the Kenyan government perspective in 2021 US$. Costs were separated into financial costs (monetary expenditures) and economic costs (financial costs plus the value of existing resources). We also separated costs by administrative level (national, regional, county, sub-county, and health facility) and program activity (advocacy and social mobilization; training; distribution, storage, and waste management; service delivery; monitoring; and supervision).

RESULTS

The total estimated cost of the pediatric influenza demonstration project was US$ 225,269 (financial) and US$ 326,691 (economic) for the year-round delivery strategy (30,397 vaccine doses administered), compared with US$ 214,753 (financial) and US$ 242,385 (economic) for the campaign strategy (25,404 doses administered). Vaccine purchase represented the largest proportion of costs for both strategies. Excluding vaccine purchase, the cost per dose administered was US$ 1.58 (financial) and US$ 5.84 (economic) for the year-round strategy and US$ 2.89 (financial) and US$ 4.56 (economic) for the campaign strategy.

CONCLUSIONS

The financial cost per dose was 83% higher for the campaign strategy than the year-round strategy due to larger expenditures for advocacy and social mobilization, training, and hiring of surge staff for service delivery. However, the economic cost per dose was more comparable for both strategies (year-round 22% higher than campaign), balanced by higher costs of operating equipment and monitoring activities for the year-round strategy. These delivery cost data provide real-world evidence to inform pediatric influenza vaccine introduction in Kenya.

Costs and cost-effectiveness of influenza illness and vaccination in low- and middle-income countries: A systematic review from 2012 to 2022

BACKGROUND

Historically, lack of data on cost-effectiveness of influenza vaccination has been identified as a barrier to vaccine use in low- and middle-income countries. We conducted a systematic review of economic evaluations describing (1) costs of influenza illness; (2) costs of influenza vaccination programs; and (3) vaccination cost-effectiveness from low- and middle-income countries to assess if gaps persist that could hinder global implementation of influenza vaccination programs.

METHODS AND FINDINGS

We performed a systematic search in Medline, Embase, Cochrane Library, CINAHL, and Scopus in January 2022 and October 2023 using a combination of the following key words: "influenza" AND "cost" OR "economic." The search included studies with publication years 2012 through 2022. Studies were eligible if they (1) presented original, peer-reviewed findings on cost of illness, cost of vaccination program, or cost-effectiveness of vaccination for seasonal influenza; and (2) included data for at least 1 low- or middle-income country. We abstracted general study characteristics and data specific to each of the 3 study types. Of 54 included studies, 26 presented data on cost-effectiveness, 24 on cost-of-illness, and 5 on program costs. Represented countries were classified as upper-middle income (UMIC; n = 12), lower-middle income (LMIC; n = 7), and low-income (LIC; n = 3). The most evaluated target groups were children (n = 26 studies), older adults (n = 17), and persons with chronic medical conditions (n = 12); fewer studies evaluated pregnant persons (n = 9), healthcare workers (n = 5), and persons in congregate living settings (n = 1). Costs-of-illness were generally higher in UMICs than in LMICs/LICs; however, the highest national economic burden, as a percent of gross domestic product and national health expenditure, was reported from an LIC. Among studies that evaluated the cost-effectiveness of influenza vaccine introduction, most (88%) interpreted at least 1 scenario per target group as either cost-effective or cost-saving, based on thresholds designated in the study. Key limitations of this work included (1) heterogeneity across included studies; (2) restrictiveness of the inclusion criteria used; and (3) potential for missed influenza burden from use of sentinel surveillance systems.

CONCLUSIONS

The 54 studies identified in this review suggest an increased momentum to generate economic evidence about influenza illness and vaccination from low- and middle-income countries during 2012 to 2022. However, given that we observed substantial heterogeneity, continued evaluation of the economic burden of influenza illness and costs/cost-effectiveness of influenza vaccination, particularly in LICs and among underrepresented target groups (e.g., healthcare workers and pregnant persons), is needed. Use of standardized methodology could facilitate pooling across settings and knowledge sharing to strengthen global influenza vaccination programs.

Seasonal influenza vaccination in the Americas: Progress and challenges during the COVID-19 pandemic

BACKGROUND

Vaccination is one of the most effective measures to prevent influenza illness and its complications; influenza vaccination remained important during the COVID-19 pandemic to prevent additional burden on health systems strained by COVID-19 demand.

OBJECTIVES

We describe policies, coverage, and progress of seasonal influenza vaccination programs in the Americas during 2019-2021 and discuss challenges in monitoring and maintaining influenza vaccination coverage among target groups during the COVID-19 pandemic.

METHODS

We used data on influenza vaccination policies and vaccination coverage reported by countries/territories via the electronic Joint Reporting Form on Immunization (eJRF) for 2019-2021. We also summarized country vaccination strategies shared with PAHO.

RESULTS

As of 2021, 39 (89 %) out of 44 reporting countries/territories in the Americas had policies for seasonal influenza vaccination. Countries/territories adapted health services and immunization delivery strategies using innovative approaches, such as new vaccination sites and expanded schedules, to ensure continuation of influenza vaccination during the COVID-19 pandemic. However, among countries/territories that reported data to eJRF in both 2019 and 2021, median coverage decreased; the percentage point decrease was 21 % (IQR = 0-38 %; n = 13) for healthcare workers, 10 % (IQR = -1.5-38 %; n = 12) for older adults, 21 % (IQR = 5-31 %; n = 13) for pregnant women, 13 % (IQR = 4.8-20.8 %; n = 8) for persons with chronic diseases, and 9 % (IQR = 3-27 %; n = 15) for children.

CONCLUSIONS

Countries/territories in the Americas successfully adapted influenza vaccination delivery to continue vaccination services during the COVID-19 pandemic; however, reported influenza vaccination coverage decreased from 2019 to 2021. Reversing declines in vaccination will necessitate strategic approaches that prioritize sustainable vaccination programs across the life course. Efforts should be made to improve the completeness and quality of administrative coverage data. Lessons learned from COVID-19 vaccination, such as the rapid development of electronic vaccination registries and digital certificates, might facilitate advances in coverage estimation.

Influenza vaccine uptake among children and older adults in China: a secondary analysis of a quasi-experimental study

BACKGROUND

Influenza vaccination is the key to prevent influenza-related disease, especially among high-risk populations. However, influenza vaccine uptake in China is low. This secondary analysis of a quasi-experimental trial aimed to understand factors associated with influenza vaccine uptake among children and older people stratified by funding context.

METHODS

A total of 225 children (aged 0.5-8 years) and 225 older people (aged 60 years or above) were recruited from three clinics (rural, suburban and urban) in Guangdong Province. Participants were allocated into two groups based on funding contexts: a self-paid group (N = 150, 75 children and 75 older adults) in which participants paid full price for their vaccination; and a subsidized group (N = 300, 150 children and 150 older adults) in which varying levels of financial support was provided. Univariate and multivariable logistic regressions were conducted stratified by funding contexts.

RESULTS

Overall, 75.0% (225/300) of participants in the subsidized group and 36.7% (55/150) in the self-paid group got vaccinated. Older adults had lower vaccination rates than children in both funding groups, while both age groups showed much higher uptake in the subsidized group than in the self-paid group (aOR = 5.96, 95% CI: 3.77-9.42, p = 0.001). In the self-paid group, having prior influenza vaccination history of children (aOR:2.61, 95%CI: 1.06-6.42) or older people (aOR:4.76, 95%CI: 1.08-20.90) was associated with increased influenza vaccine uptake compared to those who had no prior vaccination experiences in the family. While in the subsidized group, participants who got married or lived with partners (aOR = 0.32, 0.10-0.98) had lower vaccination uptake than single ones. Trust in providers' advice (aOR = 4.95, 95%CI:1.99, 12.43), perceived effectiveness of the vaccine (aOR: 12.18, 95%CI: 5.21-28.50), and experienced influenza-like illnesses in the family in the past year (aOR = 46.52, 4.10, 533.78) were associated with higher vaccine uptake.

CONCLUSIONS

Older people had suboptimal vaccine uptake compared to children in both contexts and need more attention to enhance influenza vaccination. Tailoring interventions to different vaccine funding contexts may help improve influenza vaccination: In self-paid context, motivating people to accept their first ever influenza vaccination may be a promising strategy. In subsidized context, improving public confidence in vaccine effectiveness and providers' advice would be useful.

High Clinical Burden of Influenza Disease in Adults Aged ≥ 65 Years: Can We Do Better? A Systematic Literature Review

INTRODUCTION

Influenza is a respiratory infection associated with a significant clinical burden globally. Adults aged ≥ 65 years are at increased risk of severe influenza-related symptoms and complications due to chronic comorbidity and immunosenescence. Annual influenza vaccination is recommended; however, current influenza vaccines confer suboptimal protection, in part due to antigen mismatch and poor durability. This systematic literature review characterizes the global clinical burden of seasonal influenza among adults aged ≥ 65 years.

METHODS

An electronic database search was conducted and supplemented with a conference abstract search. Included studies described clinical outcomes in the ≥ 65 years population across several global regions and were published in English between January 1, 2012 and February 9, 2022.

RESULTS

Ninety-nine publications were included (accounting for > 156,198,287 total participants globally). Clinical burden was evident across regions, with most studies conducted in the USA and Europe. Risk of influenza-associated hospitalization increased with age, particularly in those aged ≥ 65 years living in long-term care facilities, with underlying comorbidities, and infected with A(H3N2) strains. Seasons dominated by circulating A(H3N2) strains saw increased risk of influenza-associated hospitalization, intensive care unit admission, and mortality within the ≥ 65 years population. Seasonal differences in clinical burden were linked to differences in circulating strains.

CONCLUSIONS

Influenza exerts a considerable burden on adults aged ≥ 65 years and healthcare systems, with high incidence of hospitalization and mortality. Substantial influenza-associated clinical burden persists despite increasing vaccination coverage among adults aged ≥ 65 years across regions included in this review, which suggests limited effectiveness of currently available seasonal influenza vaccines. To reduce influenza-associated clinical burden, influenza vaccine effectiveness must be improved. Next generation vaccine production using mRNA technology has demonstrated high effectiveness against another respiratory virus-SARS-CoV-2-and may overcome the practical limitations associated with traditional influenza vaccine production.

Surveillance of respiratory viruses at health facilities from across Kenya, 2014

Background: Acute respiratory illnesses (ARI) are a major cause of morbidity and mortality globally.  With (re)emergence of novel viruses and increased access to childhood bacterial vaccines, viruses have assumed greater importance in the aetiology of ARI. There are now promising candidate vaccines against some of the most common endemic respiratory viruses. Optimal delivery strategies for these vaccines, and the need for interventions against other respiratory viruses, requires geographically diverse data capturing temporal variations in virus circulation. Methods: We leveraged three health facility-based respiratory illness surveillance platforms operating in 11 sites across Kenya. Nasopharyngeal (NP) and/or oropharyngeal (OP) specimens, patient demographic, and clinical characteristics were collected in 2014 from individuals of various ages presenting with respiratory symptoms at the surveillance facilities. Real time multiplex polymerase chain reaction was used to detect rhinoviruses, respiratory syncytial virus (RSV), influenza virus, human coronaviruses (hCoV), and adenoviruses. Results: From 11 sites, 5451 NP/OP specimens were collected and tested from patients. Of these, 40.2% were positive for at least one of the targeted respiratory viruses. The most frequently detected were rhinoviruses (17.0%) and RSV A/B (10.5%), followed by influenza A (6.2%), adenovirus (6.0%) and hCoV (4.2%). RSV was most prevalent among infants aged <12 months old (18.9%), adenovirus among children aged 12–23 months old (11.0%), influenza A among children aged 24–59 months (9.3%), and rhinovirus across all age groups (range, 12.7–19.0%). The overall percent virus positivity varied by surveillance site, health facility type and case definition used in surveillance. Conclusions:  We identify rhinoviruses, RSV, and influenza A as the most prevalent respiratory viruses. Higher RSV positivity in inpatient settings compared to outpatient clinics strengthen the case for RSV vaccination. To inform the design and delivery of public health interventions, long-term surveillance is required to establish regional heterogeneities in respiratory virus circulation and seasonality.

Surveillance of respiratory viruses at health facilities from across Kenya, 2014

Background: Acute respiratory illnesses (ARI) are a major cause of morbidity and mortality globally.  With (re)emergence of novel viruses and increased access to childhood bacterial vaccines, viruses have assumed greater importance in the aetiology of ARI. There are now promising candidate vaccines against some of the most common endemic respiratory viruses. Optimal delivery strategies for these vaccines, and the need for interventions against other respiratory viruses, requires geographically diverse data capturing temporal variations in virus circulation. Methods: We leveraged three health facility-based respiratory illness surveillance platforms operating in 11 sites across Kenya. Nasopharyngeal (NP) and/or oropharyngeal (OP) specimens, patient demographic, and clinical characteristics were collected in 2014 from individuals of various ages presenting with respiratory symptoms at the surveillance facilities. Real time multiplex polymerase chain reaction was used to detect rhinoviruses, respiratory syncytial virus (RSV), influenza virus, human coronaviruses (hCoV), and adenoviruses. Results: From 11 sites, 5451 NP/OP specimens were collected and tested from patients. Of these, 40.2% were positive for at least one of the targeted respiratory viruses. The most frequently detected were rhinoviruses (17.0%) and RSV A/B (10.5%), followed by influenza A (6.2%), adenovirus (6.0%) and hCoV (4.2%). RSV was most prevalent among infants aged <12 months old (18.9%), adenovirus among children aged 12–23 months old (11.0%), influenza A among children aged 24–59 months (9.3%), and rhinovirus across all age groups (range, 12.7–19.0%). The overall percent virus positivity varied by surveillance site, health facility type and case definition used in surveillance. Conclusions:  We identify rhinoviruses, RSV, and influenza A as the most prevalent respiratory viruses. Higher RSV positivity in inpatient settings compared to outpatient clinics strengthen the case for RSV vaccination. To inform the design and delivery of public health interventions, long-term surveillance is required to establish regional heterogeneities in respiratory virus circulation and seasonality.

The Role of Psychological Factors and Vaccine Conspiracy Beliefs in Influenza Vaccine Hesitancy and Uptake among Jordanian Healthcare Workers during the COVID-19 Pandemic

Vaccination to prevent influenza virus infection and to lessen its severity is recommended among healthcare workers (HCWs). Health professionals have a higher risk of exposure to viruses and could transmit the influenza virus to vulnerable patients who are prone to severe disease and mortality. The aim of the current study was to evaluate the levels of influenza vaccine acceptance and uptake as well as its determinants, among Jordanian HCWs over the last influenza season of 2021/2022. This study was based on a self-administered electronic survey that was distributed in March 2022. Psychological determinants of influenza vaccine acceptance and vaccine conspiracy beliefs were assessed using the previously validated 5C scale questionnaire (confidence, complacency, constraints, calculation and collective responsibility) and the vaccine conspiracy beliefs scale. The study sample comprised a total of 1218 HCWs: nurses (n = 412, 33.8%), physicians (n = 367, 30.1%), medical technicians (n = 182, 14.9%), pharmacists (n = 161, 13.2%) and dentists (n = 87, 7.1%), among others. About two-thirds of the study sample expressed willingness to receive influenza vaccination if provided free of charge (n = 807, 66.3%), whereas less than one-third were willing to pay for the vaccine (n = 388, 31.9%). The self-reported uptake of the influenza vaccine in the last influenza season was 62.8%. The following factors were significantly associated with higher acceptance of influenza vaccination if provided freely, as opposed to vaccine hesitancy/rejection: male sex; physicians and dentists among HCW categories; higher confidence and collective responsibility; and lower complacency, constraints and calculation. Higher influenza vaccine uptake was significantly correlated with nurses and physicians among HCW categories, older age, a higher monthly income, higher confidence and collective responsibility, lower complacency and constraints and lower embrace of general vaccine conspiracy beliefs. The results of the current study can provide helpful clues to improve influenza vaccine coverage among HCWs in Jordan. Consequently, this can help to protect vulnerable patient groups and reserve valuable resources in healthcare settings. Psychological determinants appeared to be the most significant factors for vaccine acceptance and uptake, whereas the embrace of general vaccine conspiracy beliefs was associated with lower rates of influenza vaccine uptake, which should be considered in educational and interventional measures aiming to promote influenza vaccination.

Association between risk perception and influenza vaccine hesitancy for children among reproductive women in China during the COVID-19 pandemic: a national online survey

BACKGROUND

In China, the national prevalence of parental influenza vaccine hesitancy (IVH) during the pandemic of coronavirus disease 2019 (COVID-19), and the association between risk perception and parental IVH are still unclear. We aimed to explore the association between risk perception and IVH for children among reproductive women in China, a poorly studied area.

METHODS

From December 14, 2020, to January 31, 2021, we conducted a national anonymous online survey on IVH for children among reproductive women in China. We assessed risk perception including perceived susceptibility, severity, barriers, and benefits using the Health Belief Model and then classified each variable into three groups based on tertiles. Logistic regression models were used to calculate the adjusted odds ratio (aOR) of risk perception related to vaccine hesitancy after controlling for sociodemographic characteristics, health status, and knowledge of influenza, among other factors. Additionally, subgroup analysis was performed.

RESULTS

Among 3,011 reproductive women, 9.13% reported IVH. In multivariable models, vaccine hesitancy was associated with low perceived susceptibility (aOR = 2.55, 95% CI: 1.79-3.65), higher perceived barriers (moderate: aOR = 1.47, 95% CI: 1.04-2.08; high: aOR = 2.20, 95% CI: 1.47-3.30), and low perceived benefit (moderate: aOR = 1.40, 95% CI: 1.03-1.92; low: aOR = 2.10, 95% CI: 1.43-3.07). Subgroup analysis showed that vaccine hesitancy was more likely to occur among women with high perceived barriers aged < 30 years compared with those older than 30 years (P for difference = 0.041) and among women with moderate perceived benefit who had never conceived compared with those had a history of pregnancy (P for difference = 0.048).

CONCLUSIONS

Nearly one in 10 reproductive women was hesitant about influenza vaccination for their children during the COVID-19 pandemic. To mitigate vaccine hesitancy, our findings highlight a need for tailored public health measures to increase perceived disease susceptibility and vaccine benefit and decrease perceived barriers. Furthermore, the effect of high perceived barriers and moderate perceived benefit on vaccine hesitancy was higher among younger women and women who had never conceived.

Cost-effectiveness of seasonal influenza vaccination in pregnant women, healthcare workers and adults >= 60 years of age in Lao People's Democratic Republic

BACKGROUND

Pregnant women, healthcare workers (HW), and adults >= 60 years have shown an increased vulnerability to seasonal influenza virus infections and/or complications. In 2012, the Lao People's Democratic Republic (Lao PDR) initiated a national influenza vaccination program for these target groups. A cost-effectiveness evaluation of this program was undertaken to inform program sustainability.

METHODS

We designed a decision-analytical model and collected influenza-related medical resource utilization and cost data, including indirect costs. Model inputs were obtained from medical record abstraction, interviews of patients and staff at hospitals in the national influenza sentinel surveillance system and/or from literature reviews. We compared the annual disease and economic impact of influenza illnesses in each of the target groups in Lao PDR under scenarios of no vaccination and vaccination, and then estimated the cost-effectiveness of the vaccination program. We performed sensitivity analyses to identify influential variables.

RESULTS

Overall, the vaccination of pregnant women, HWs, and adults >= 60 years could annually save 11,474 doctor visits, 1,961 days of hospitalizations, 43,027 days of work, and 1,416 life-years due to laboratory-confirmed influenza illness. After comparing the total vaccination program costs of 23.4 billion Kip, to the 18.4 billion Kip saved through vaccination, we estimated the vaccination program to incur a net cost of five billion Kip (599,391 USD) annually. The incremental cost per life-year saved (ICER) was 44 million Kip (5,295 USD) and 6.9 million Kip (825 USD) for pregnant women and adults >= 60 years, respectively. However, vaccinating HWs provided societal cost-savings, returning 2.88 Kip for every single Kip invested. Influenza vaccine effectiveness, attack rate and illness duration were the most influential variables to the model.

CONCLUSION

Providing influenza vaccination to HWs in Lao PDR is cost-saving while vaccinating pregnant women and adults >= 60 is cost-effective and highly cost-effective, respectively, per WHO standards.

Pichia pastoris (Komagataella phaffii) as a Cost-Effective Tool for Vaccine Production for Low- and Middle-Income Countries (LMICs)

Vaccination is of paramount importance to global health. With the advent of the more recent pandemics, the urgency to expand the range has become even more evident. However, the potential limited availability and affordability of vaccines to resource low- and middle-income countries has created a need for solutions that will ensure cost-effective vaccine production methods for these countries. Pichia pastoris (P. pastoris) (also known as Komagataella phaffii) is one of the most promising candidates for expression of heterologous proteins in vaccines development. It combines the speed and ease of highly efficient prokaryotic platforms with some key capabilities of mammalian systems, potentially reducing manufacturing costs. This review will examine the latest developments in P. pastoris from cell engineering and design to industrial production systems with focus on vaccine development and with reference to specific key case studies.