Early B cell transcriptomic markers of measles-specific humoral immunity following a 3rd dose of MMR vaccine.

B cell transcriptomic signatures hold promise for the early prediction of vaccine-induced humoral immunity and vaccine protective efficacy. We performed a longitudinal study in 232 healthy adult participants before/after a 3rd dose of MMR (MMR3) vaccine. We assessed baseline and early transcriptional patterns in purified B cells and their association with measles-specific humoral immunity after MMR vaccination using two analytical methods ("per gene" linear models and joint analysis). Our study identified distinct early transcriptional signatures/genes following MMR3 that were associated with measles-specific neutralizing antibody titer and/or binding antibody titer. The most significant genes included: the interleukin 20 receptor subunit beta/IL20RB gene (a subunit receptor for IL-24, a cytokine involved in the germinal center B cell maturation/response); the phorbol-12-myristate-13-acetate-induced protein 1/PMAIP1, the brain expressed X-linked 2/BEX2 gene and the B cell Fas apoptotic inhibitory molecule/FAIM, involved in the selection of high-affinity B cell clones and apoptosis/regulation of apoptosis; as well as IL16 (encoding the B lymphocyte-derived IL-16 ligand of CD4), involved in the crosstalk between B cells, dendritic cells and helper T cells. Significantly enriched pathways included B cell signaling, apoptosis/regulation of apoptosis, metabolic pathways, cell cycle-related pathways, and pathways associated with viral infections, among others. In conclusion, our study identified genes/pathways linked to antigen-induced B cell proliferation, differentiation, apoptosis, and clonal selection, that are associated with, and impact measles virus-specific humoral immunity after MMR vaccination.

Detection of SARS-CoV-2-Specific Cells Utilizing Whole Proteins and/or Peptides in Human PBMCs Using IFN-Æ´ ELISPOT Assay.

SARS-CoV-2 continues to threaten global public health, making COVID-19 immunity studies of utmost importance. Waning of antibody responses postinfection and/or vaccination and the emergence of immune escape variants have been ongoing challenges in mitigating SARS-CoV-2 morbidity and mortality. While a tremendous amount of work has been done to characterize humoral immune responses to SARS-CoV-2 virus and vaccines, cellular immunity, mediated by T cells, is critical for efficient viral control and protection and demonstrates high durability and cross-reactivity to coronavirus variants. Thus, ELISPOT, a standard assay for antigen-specific cellular immune response assessment, allows us to evaluate SARS-CoV-2-specific T-cell response by quantifying the frequency of SARS-CoV-2-specific cytokine-secreting cells in vitro. We have outlined a detailed procedure to study T-cell recall responses to SARS-CoV-2 in human peripheral blood mononuclear cells (PBMCs) following infection and/or vaccination using an optimized IFN-γ ELISPOT assay. Our methodologies can be adapted to assess other cytokines and are a useful tool for studying other viral pathogen and/or peptide-specific T-cell responses.

Frequencies of SARS-CoV-2 Spike Protein-Specific Memory B Cells in Human PBMCs, Quantified by ELISPOT Assay.

Vaccination against SARS-CoV-2 with coronavirus vaccines that elicit protective immune responses is critical to the prevention of severe disease and mortality associated with SARS-CoV-2 infection. Understanding the adaptive immune responses to SARS-CoV-2 infection and/or vaccination will continue to aid in the development of next-generation vaccines. Studies have shown the important role of SARS-CoV-2-specific antibodies for both disease resolution and prevention of COVID-19 serious sequelae following vaccination. However, antibody responses are short-lived, highlighting the importance of studying antigen-specific B-cell responses to better understand durable immunity and immunologic memory. Since the spike protein is the main target of antibody-producing B cells, we developed a SARS-CoV-2 memory B cell ELISPOT assay to measure the frequencies of spike-specific B cells after COVID-19 infection and/or vaccination. Here, we describe in detail the methodology for using this ELISPOT assay to quantify SARS-CoV-2 spike-specific memory B cells produced by infection and/or vaccination in human PBMC samples. Application of this assay may help better understand and predict SARS-CoV-2 recall immune responses and to develop potential B cell correlates of protection at the methodological level.

Polygenic Prediction of Cellular Immune Responses to Mumps Vaccine.

In this report, we provide a follow-up analysis of a previously published genome-wide association study of host genetic variants associated with inter-individual variations in cellular immune responses to mumps vaccine. Here we report the results of a polygenic score (PGS) analysis showing how common variants can predict mumps vaccine response. We found higher PGS for IFNγ, IL-2, and TNFα were predictive of higher post-vaccine IFNγ (p-value = 2e-6), IL-2 (p = 2e-7), and TNFα (p = 0.004) levels, respectively. Control of immune responses after vaccination is complex and polygenic in nature. Our results suggest that the PGS-based approach enables better capture of the combined genetic effects that contribute to mumps vaccine-induced immunity, potentially offering a more comprehensive understanding than traditional single-variant GWAS. This approach will likely have broad utility in studying genetic control of immune responses to other vaccines and to infectious diseases.

Restricted Omicron-specific cross-variant memory B-cell immunity after a 3rd dose/booster of monovalent Wuhan-Hu-1-containing COVID-19 mRNA vaccine.

The responsiveness/cross-binding of vaccine-induced memory B cells/MBCs to previous and emerging divergent SARS-CoV-2 variants (e.g., Omicron) is understudied. In this longitudinal study subjects receiving two or three doses of monovalent ancestral strain-containing COVID-19 mRNA vaccine were evaluated. In contrast to others, we observed significantly lower frequencies of MBCs reactive to the receptor-binding domain/RBD, the N-terminal domain/NTD, and the S1 of Omicron/BA.1, compared to Wuhan and Delta, even after a 3rd vaccine dose/booster. Our study is a proof of concept that MBC cross-reactivity to variants with greater sequence divergence from the vaccine strain may be overestimated and suggests that these variants may exhibit immune escape with reduced recognition by circulating pre-existing MBCs upon infection.

A multifaceted approach for identification, validation, and immunogenicity of naturally processed and in silico-predicted highly conserved SARS-CoV-2 peptides.

SARS-CoV-2 remains a major global public health concern. Antibody waning and immune escape variant emergence necessitate the development of next generation vaccines that induce cross-reactive durable immune responses. T cell responses to SARS-CoV-2 demonstrate higher conservation, antigenic breadth, and longevity than antibody responses. Therefore, we sought to identify pathogen-derived T cell epitopes for a potential peptide-based vaccine. We pursued an approach leveraging: 1) liquid chromatography and tandem mass spectrometry (LC-MS/MS)-based identification of peptides from ancestral SARS-CoV-2-infected cell lines, 2) epitope prediction algorithms, and 3) overlapping peptide libraries. From this strategy, we identified 380 unique SARS-CoV-2-derived peptide sequences, including 53 antigenic HLA class I and class II peptides from multiple structural and non-structural/accessory viral proteins. These peptide sequences were highly conserved across variants of concern/interest (VoC/VoIs), and are estimated to achieve coverage of >96% of the world population. Our findings validate this discovery pipeline for peptide identification and immunogenicity testing, and are a crucial step toward the development of a next-generation multi-epitope SARS-CoV-2 peptide vaccine, and a novel vaccine platform methodology.

Associations of adaptive immune cell subsets with measles, mumps, and Rubella-Specific immune response outcomes.

The measles-mumps-rubella (MMR) vaccine has been widely used in the US, but measles and mumps outbreaks remain a public health issue in the US and elsewhere, even among individuals immunized with 2 doses of the vaccine. Immune correlates of vaccine-elicited protection against disease are typically assessed with serum antibody assays, but in some cases, these correlates fail to predict immunity, with the complexity and heterogeneity of the immune response. We used multicolor flow cytometry to evaluate changes in the frequency of peripheral T and B cell subsets in 82 study participants after receipt of a third dose of the M-M-RII vaccine (Merck & Co, Inc). We assessed correlations between flow cytometry variables and measles virus (MV), mumps virus (MuV), or rubella virus (RV)-specific immune response outcomes. Following a third vaccine dose, major changes were observed in the T-cell compartment. CD4+ T cell subsets were significantly increased from baseline to day 28, whereas CD8+ T cell subsets were predominantly decreased. Changes in regulatory T cells (Tregs) correlated with RV- and MV-specific immune outcomes and with high- and low-RV antibody responder groups, implicating the importance of Tregs in regulating MMR vaccine-induced immune responses. This information may help define additional correlates of protection and aid in the design of improved vaccines.

Excessive daytime sleepiness is associated with impaired antibody response to influenza vaccination in older male adults.

Background: The reduced effectiveness of standard-dose influenza vaccines in persons ≥65 years of age led to the preferential recommendation to use high-dose (HDFlu) or MF59-adjuvanted (MF59Flu) vaccines for this age group. Sleep is an important modulator of immune responses to vaccines and poor sleep health is common in older adults. However, potential effects of poor sleep health on immune responses to influenza vaccination in older adults remain largely unknown. Methods: We conducted a cohort study of 210 healthy participants age ≥65 years, who received either seasonal high-dose (HDFlu) or MF59-adjuvanted (MF59Flu) influenza vaccine. We assessed sleep characteristics in this cohort by standardized questionnaires and measured the antibody titer against influenza A/H3N2 virus in serum of study participants by hemagglutination inhibition assay on the day of immunization and 28 days thereafter. We then assessed the association between sleep characteristics and antibody titers. Results: Our results demonstrated that male, but not female, study participants with excessive daytime sleepiness had an impaired influenza A/H3N2-specific antibody response at Day 28 post-vaccination. No other associations were found between antibody titer and other sleep characteristics, including sleep quality and obstructive sleep apnea. Conclusion: Our results provide an additional and easily measured variable explaining poor vaccine effectiveness in older adults. Our results support that gaining sufficient sleep is a simple non-vaccine interventional approach to improve influenza immune responses in older adults. Our findings extend the literature on the negative influence of excessive daytime sleepiness on immune responses to influenza vaccination in older male adults.

Genome-wide determinants of cellular immune responses to mumps vaccine.

BACKGROUND: We have previously described genetic polymorphisms in candidate genes that are associated with inter-individual variations in antibody responses to mumps vaccination. To expand upon our previous work, we performed a genome-wide association study (GWAS) to discover host genetic variants associated with mumps vaccine-induced cellular immune responses. METHODS: We performed a GWAS of mumps-specific immune response outcomes (11 secreted cytokines/chemokines) in a cohort of 1,406 subjects. RESULTS: Among the 11 cytokine/chemokines we studied, four (IFN-γ, IL-2, IL-1ß, and TNFα) demonstrated GWAS signals reaching genome-wide significance (p < 5 × 10-8). A genomic region (encoding Sialic acid-binding immunoglobulin-type lectins/SIGLEC) located on chromosome 19q13 (p < 5 × 10-8) was associated with both IL-1ß and TNFα responses. The SIGLEC5/SIGLEC14 region contained 11 statistically significant single nucleotide polymorphisms (SNPs), including the intronic SIGLEC5 rs872629 (p = 1.3E-11) and rs1106476 (p = 1.32E-11) whose alternate alleles were significantly associated with decreased levels of mumps-specific IL-1ß (rs872629, p = 1.77E-09; rs1106476, p = 1.78E-09) and TNFα (rs872629, p = 1.3E-11; rs1106476, p = 1.32E-11) production. CONCLUSIONS: Our results suggest that SNPs in the SIGLEC5/SIGLEC14 genes play a role in cellular and inflammatory immune responses to mumps vaccination. These findings motivate further research into the functional roles of SIGLEC genes in the regulation of mumps vaccine-induced immunity.

Virus-specific and shared gene expression signatures in immune cells after vaccination in response to influenza and vaccinia stimulation.

Background: In the vaccine era, individuals receive multiple vaccines in their lifetime. Host gene expression in response to antigenic stimulation is usually virus-specific; however, identifying shared pathways of host response across a wide spectrum of vaccine pathogens can shed light on the molecular mechanisms/components which can be targeted for the development of broad/universal therapeutics and vaccines. Method: We isolated PBMCs, monocytes, B cells, and CD8+ T cells from the peripheral blood of healthy donors, who received both seasonal influenza vaccine (within <1 year) and smallpox vaccine (within 1 - 4 years). Each of the purified cell populations was stimulated with either influenza virus or vaccinia virus. Differentially expressed genes (DEGs) relative to unstimulated controls were identified for each in vitro viral infection, as well as for both viral infections (shared DEGs). Pathway enrichment analysis was performed to associate identified DEGs with KEGG/biological pathways. Results: We identified 2,906, 3,888, 681, and 446 DEGs in PBMCs, monocytes, B cells, and CD8+ T cells, respectively, in response to influenza stimulation. Meanwhile, 97, 120, 20, and 10 DEGs were identified as gene signatures in PBMCs, monocytes, B cells, and CD8+ T cells, respectively, upon vaccinia stimulation. The majority of DEGs identified in PBMCs were also found in monocytes after either viral stimulation. Of the virus-specific DEGs, 55, 63, and 9 DEGs occurred in common in PBMCs, monocytes, and B cells, respectively, while no DEGs were shared in infected CD8+ T cells after influenza and vaccinia. Gene set enrichment analysis demonstrated that these shared DEGs were over-represented in innate signaling pathways, including cytokine-cytokine receptor interaction, viral protein interaction with cytokine and cytokine receptor, Toll-like receptor signaling, RIG-I-like receptor signaling pathways, cytosolic DNA-sensing pathways, and natural killer cell mediated cytotoxicity. Conclusion: Our results provide insights into virus-host interactions in different immune cells, as well as host defense mechanisms against viral stimulation. Our data also highlights the role of monocytes as a major cell population driving gene expression in ex vivo PBMCs in response to viral stimulation. The immune response signaling pathways identified in this study may provide specific targets for the development of novel virus-specific therapeutics and improved vaccines for vaccinia and influenza. Although influenza and vaccinia viruses have been selected in this study as pathogen models, this approach could be applicable to other pathogens.

Genome-Wide Determinants of Cellular Immune Responses to Mumps Vaccine.

Background: We have previously described genetic polymorphisms in candidate genes that are associated with inter-individual variations in antibody responses to mumps vaccination. To expand upon our previous work, we performed a genome-wide association study (GWAS) to discover host genetic variants associated with mumps vaccine-induced cellular immune responses. Methods: We performed a GWAS of mumps-specific immune response outcomes (11 secreted cytokines/chemokines) in a cohort of 1,406 subjects. Results: Among the 11 cytokine/chemokines we studied, four (IFN-γ, IL-2, IL-1ß, and TNFα) demonstrated GWAS signals reaching genome-wide significance (p<5 x 10 -8 ). A genomic region (encoding Sialic acid-binding immunoglobulin-type lectins/SIGLEC) located on chromosome 19q13 (p<5×10 -8 ) was associated with both IL-1ß and TNFα responses. The SIGLEC5/SIGLEC14 region contained 11 statistically significant single nucleotide polymorphisms (SNPs), including the intronic SIGLEC5 rs872629 (p=1.3E-11) and rs1106476 (p=1.32E-11) whose alternate alleles were significantly associated with decreased levels of mumps-specific IL-1ß (rs872629, p=1.77E-09; rs1106476, p=1.78E-09) and TNFα (rs872629, p=1.3E-11; rs1106476, p=1.32E-11) production. Conclusions: Our results suggest that SNPs in the SIGLEC5/SIGLEC14 genes play a role in cellular and inflammatory immune responses to mumps vaccination. These findings motivate further research into the functional roles of SIGLEC genes in the regulation of mumps vaccine-induced immunity.

T Cell Transcriptional Signatures of Influenza A/H3N2 Antibody Response to High Dose Influenza and Adjuvanted Influenza Vaccine in Older Adults.

Older adults experience declining influenza vaccine-induced immunity and are at higher risk of influenza and its complications. For this reason, high dose (e.g., Fluzone) and adjuvanted (e.g., Fluad) vaccines are preferentially recommended for people age 65 years and older. However, T cell transcriptional activity shaping the humoral immune responses to Fluzone and Fluad vaccines in older adults is still poorly understood. We designed a study of 234 older adults (≥65 years old) who were randomly allocated to receive Fluzone or Fluad vaccine and provided blood samples at baseline and at Day 28 after immunization. We measured the humoral immune responses (hemagglutination inhibition/HAI antibody titer) to influenza A/H3N2 and performed mRNA-Seq transcriptional profiling in purified CD4+ T cells, in order to identify T cell signatures that might explain differences in humoral immune response by vaccine type. Given the large differences in formulation (higher antigen dose vs adjuvant), our hypothesis was that each vaccine elicited a distinct transcriptomic response after vaccination. Thus, the main focus of our study was to identify the differential gene expression influencing the antibody titer in the two vaccine groups. Our analyses identified three differentially expressed, functionally linked genes/proteins in CD4+ T cells: the calcium/calmodulin dependent serine/threonine kinase IV (CaMKIV); its regulator the TMEM38B/transmembrane protein 38B, involved in maintenance of intracellular Ca2+ release; and the transcriptional coactivator CBP/CREB binding protein, as regulators of transcriptional activity/function in CD4+ T cells that impact differences in immune response by vaccine type. Significantly enriched T cell-specific pathways/biological processes were also identified that point to the importance of genes/proteins involved in Th1/Th2 cell differentiation, IL-17 signaling, calcium signaling, Notch signaling, MAPK signaling, and regulation of TRP cation Ca2+ channels in humoral immunity after influenza vaccination. In summary, we identified the genes/proteins and pathways essential for cell activation and function in CD4+ T cells that are associated with differences in influenza vaccine-induced humoral immunity by vaccine type. These findings provide an additional mechanistic perspective for achieving protective immunity in older adults.

Seroprevalence of Measles Antibodies in a Highly MMR-Vaccinated Population.

As an extremely contagious pathogen, a high rate of vaccine coverage and the durability of vaccine-induced immunity are key factors to control and eliminate measles. Herein, we assessed the seroprevalence of antibodies specific to measles in a cohort of 1393 adults (20-44 years old). ELISA results showed a nontrivial proportion of 37.6% study subjects being negative for measles immunoglobulin G (IgG). We also found significant influences of sex and age of the study cohort on the IgG level. Our findings suggest that even within a highly vaccinated population, a subset of individuals may still have sub-optimal immunity against measles and potentially be susceptible during any future measles outbreaks.

Evaluating immunogenicity of pathogen-derived T-cell epitopes to design a peptide-based smallpox vaccine.

Despite the eradication in 1980, developing safe and effective smallpox vaccines remains an active area of research due to the recent outbreaks and the public health concern that smallpox viruses could be used as bioterrorism weapons. Identifying immunogenic peptides (epitopes) would create a foundation for the development of a robust peptide-based vaccine. We previously identified a library of naturally-processed, human leukocyte antigen class I-presented vaccinia-derived peptides from infected B cells. In the current study, we evaluated the immunogenicity of these T-cell peptides in both transgenic mouse models and human peripheral blood mononuclear cells. A vaccine based on four selected peptides provided 100% protection against a lethal viral challenge. In addition, responses from memory T cells remained unchanged up to five months. Our results validate a practical approach for identifying and verifying immunogenic peptides for vaccine development and highlight the potential of peptide-based vaccines for various infectious diseases.

The Influence of Sex, Body Mass Index, and Age on Cellular and Humoral Immune Responses Against Measles After a Third Dose of Measles-Mumps-Rubella Vaccine.

BACKGROUND: A third dose of measles-mumps-rubella vaccine (MMR3) is recommended in mumps outbreak scenarios, but the immune response and the need for widespread use of MMR3 remain uncertain. Herein, we characterized measles-specific immune responses to MMR3 in a cohort of 232 healthy subjects. METHODS: Serum and peripheral blood mononuclear cells (PBMCs) were sampled at day 0 and day 28 after MMR3. Measles-specific binding and neutralizing antibodies were quantified in sera by enzyme-linked immunosorbent assay and a microneutralization assay, respectively. PBMCs were stimulated with inactivated measles virus, and the release of cytokines/chemokines was assessed by a multiplex assay. Demographic variables of subjects were examined for potential correlations with immune outcomes. RESULTS: Of the study participants, 95.69% and 100% were seropositive at day 0 and day 28, respectively. Antibody avidity significantly increased from 38.08% at day 0 to 42.8% at day 28 (P = .00026). Neutralizing antibodies were significantly enhanced, from 928.7 at day 0 to 1289.64 mIU/mL at day 28 (P = .0001). Meanwhile, cytokine/chemokine responses remained largely unchanged. Body mass index was significantly correlated with the levels of inflammatory cytokines/chemokines. CONCLUSIONS: Measles-specific humoral immune responses, but not cellular responses, were enhanced after MMR3 receipt, extending current understanding of immune responses to MMR3 and supporting MMR3 administration to seronegative or high-risk individuals.

Detection of SARS-CoV-2 peptide-specific antibodies in Syrian hamster serum by ELISA.

Golden Syrian hamsters are increasingly used as a permissive animal model for SARS-CoV-2 virus studies, but the lack of immunological assays and other immunological reagents for hamsters limits its full potential. Herein, we developed an ELISA method to detect antibodies specific to peptides and proteins derived from SARS-CoV-2 virus in immunized golden Syrian hamsters. Under optimized conditions, this assay quantitates antibodies specific for individual viral peptides, peptide pools, and proteins. Hence, this ELISA method allows investigators to quantitatively assess humoral immune responses at the peptide and protein levels and has potential application in the development of peptide-based vaccines to be tested in hamsters.

Distinct Homologous and Variant-Specific Memory B-Cell and Antibody Response Over Time After Severe Acute Respiratory Syndrome Coronavirus 2 Messenger RNA Vaccination.

The durability of protective humoral immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infection is largely dependent on the generation and persistence of antigen-specific isotype-switched memory B cells (MBCs) and long-lived plasma cells that reside in the bone marrow and secrete high-affinity neutralizing antibodies. The reactivity of vaccine-induced MBCs to emerging clinically significant SARS-CoV-2 variants of concern (VoCs) is largely unknown. In a longitudinal cohort study (up to 6 months following coronavirus disease 2019 messenger RNA vaccination), we measured MBCs in concert with other functional antibody measures. We found statistically significant differences between the frequencies of MBCs responding to homologous and VoC (Beta, Gamma, and Delta) receptor-binding domains after vaccination that persisted over time. In concert with a waning antibody response, the reduced MBC response to VoCs could translate to a weaker subsequent recall immune response and increased susceptibility to the emerging SARS-CoV-2 variant strains after vaccination.

Proteomic assessment of humoral immune responses in smallpox vaccine recipients.

The availability of effective smallpox vaccines was a critical element of the successful eradication of smallpox in 1980. Antibody responses play a primary role in protective immunity and neutralizing antibody is an established correlate of protection against smallpox. In this study we used a poxvirus proteome array to assess the antibody response to individual viral proteins in a cohort of 1,037 smallpox vaccine recipients. Several statistically significant differences were observed in the antibody response to immunodominant proteins between men and women, including B5R-a major target of neutralizing antibody in vaccinia immune globulin, and the membrane proteins D8L and A27L, both of which have been used as vaccine antigens providing protection in animal models. We also noted differences across racial/ethnic groups. In this cohort, which consisted of both ACAM2000 and Dryvax recipients, we noted minute differences in the antibody responses to a restricted number of viral proteins, providing additional support for the use of ACAM2000 as a replacement smallpox vaccine. Furthermore, our data indicate that poxvirus proteome microarrays can be valuable for screening and monitoring smallpox vaccine-induced humoral immune responses in large-scale serologic surveillance studies and prove useful in the guidance of developing novel smallpox candidate vaccines.

Mumps virus-specific immune response outcomes and sex-based differences in a cohort of healthy adolescents.

Despite high levels of MMR-II usage in the US, mumps outbreaks continue to occur. Evidence suggests that mumps vaccine-induced humoral immunity wanes over time. Relatively few studies have examined cell-mediated immunity or reported on sex-based differences. To better understand sex-based differences in the immune response to mumps vaccine, we measured neutralizing antibody titers and mumps-specific cytokine/chemokine responses in a cohort of 748 adolescents and young adults after two doses of MMR vaccine. We observed significantly higher neutralizing antibody titers in females than in males (120.8 IU/mL, 98.7 IU/mL, p = 0.038) but significantly higher secretion levels of MIP-1α, MIP-1ß, TNFα, IL-6, IFNγ, and IL-1ß in males compared to females. These data demonstrate that sex influences mumps-specific humoral and cell-mediated immune response outcomes, a phenomenon that should be considered during efforts to improve vaccines and prevent future outbreaks.

Update on Influenza Vaccines: Needs and Progress.

Influenza is an annual seasonal epidemic, and occasionally pandemic, respiratory disease that causes considerable morbidity and mortality worldwide. Despite the widespread availability of safe and effective vaccines since the 1950s, this virus continues to pose a significant public health threat. Variable and often weak vaccine effectiveness, antigenic drift and shift, and vaccine hesitancy are some of the obstacles that must be overcome to control this disease. In this article, we briefly review current influenza vaccines, address safety concerns and the need for newer influenza vaccines of higher efficacy, and discuss efforts to create broadly protective, universal influenza vaccines.