Materiały źródłowe

• #1 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Influenza is a vaccine preventable disease and vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to risk groups. […] The effectiveness of current influenza is suboptimal, being estimated as 40% to 60% when the vaccines strains are antigenically well-matched with the circulating viruses. […] Overall, influenza vaccines are effective against morbidity and mortality in all age and risk groups, especially in young children and older adults. […] However, the effectiveness is dependent on several factors such as the age of vaccinees, the match between the strain included in the vaccine composition and the circulating virus, egg-adaptations occurring during the production process, and the subjects history of previous vaccination.

• #2 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Overall, the consensus is that vaccination is protective in children, though age-related differences were found in some cases and the lowest protection was observed against H3N2. […] Overall, it is commonly accepted in the scientific and medical communities that vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to (high-) risk groups such as young children, elderly adults, persons with chronic medical conditions, and immunocompromised persons. […] However, the outcome of such effectiveness studies is very dependent on influenza virus-specific parameters, mainly the antigenic drift, especially of the A-strains or the differently circulating B-strains of the two divergent lineages B-Victoria and B-Yamagata.

• #3 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  Interim 20242025 seasonal influenza VE estimates were derived from four U.S. VE networks. Among children and adolescents, VE was 32%, 59%, and 60% in outpatient settings (three networks) and 63% and 78% against influenza-associated hospitalization (two networks). Among adults, VE was 36% and 54% in outpatient settings (two networks) and 41% and 55% against influenza-associated hospitalization (two networks). […] Vaccination with the 20242025 influenza vaccine reduced the risk for influenza-associated outpatient visits and hospitalization. These findings support recommendations that all eligible persons aged 6 months should receive an annual influenza vaccination. Vaccination should be offered as long as influenza viruses are circulating. […] Preliminary estimates indicate that receipt of the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and influenza-associated hospitalization.

• #4 2024-2025 Flu Vaccine Effectiveness: What Do We Know?

  https://www.flu.com/Articles/2024/2024-2025-Flu-Vaccine-Effectiveness

  With the flu season now well underway in the Northern Hemisphere, you might be wondering about the effectiveness of this seasons flu vaccine. […] According to the newly released CDC report, vaccine effectiveness against any influenza in children and adolescents was between 32% and 60% in outpatient settings, and between 63% and 78% against influenza-associated hospitalization. For adults aged 18 and older, vaccine effectiveness was 36% to 54% in outpatient settings and 41% to 55% against hospitalization. […] Based on last year’s Southern Hemisphere data, experts estimated that the Northern Hemisphere flu vaccine would reduce the risk of hospitalization due to the flu by around 35%, once all data is collected for the 20242025 flu season. […] Flu vaccine effectiveness for influenza A(H3N2) strains tends to be lower than for Influenza A(H1N1) and Influenza B viruses.

• #5 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  Interim 20242025 seasonal influenza VE estimates were derived from four U.S. VE networks. Among children and adolescents, VE was 32%, 59%, and 60% in outpatient settings (three networks) and 63% and 78% against influenza-associated hospitalization (two networks). Among adults, VE was 36% and 54% in outpatient settings (two networks) and 41% and 55% against influenza-associated hospitalization (two networks). […] Vaccination with the 20242025 influenza vaccine reduced the risk for influenza-associated outpatient visits and hospitalization. These findings support recommendations that all eligible persons aged 6 months should receive an annual influenza vaccination. Vaccination should be offered as long as influenza viruses are circulating. […] Preliminary estimates indicate that receipt of the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and influenza-associated hospitalization.

• #6 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  These interim estimates of 202425 VE indicate that influenza vaccination was effective in preventing medically attended influenza-associated illness in children, adolescents, and adults in the United States. Among children and adolescents, VE against medically attended influenza ranged from 32% to 60% in outpatient settings and from 63% to 78% against influenza-associated hospitalization. Among adults, VE against medically attended influenza was 36% and 54% in two outpatient settings and 41% and 55% against influenza-associated hospitalization. […] Findings in this report show that vaccination with the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and support CDCs recommendation that all persons aged 6 months be vaccinated against influenza. These findings also support the strong protective effect influenza vaccination has against influenza-associated hospitalization, demonstrating the importance of vaccination to reduce more severe influenza-associated complications.

• #7 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Influenza is a vaccine preventable disease and vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to risk groups. […] The effectiveness of current influenza is suboptimal, being estimated as 40% to 60% when the vaccines strains are antigenically well-matched with the circulating viruses. […] Overall, influenza vaccines are effective against morbidity and mortality in all age and risk groups, especially in young children and older adults. […] However, the effectiveness is dependent on several factors such as the age of vaccinees, the match between the strain included in the vaccine composition and the circulating virus, egg-adaptations occurring during the production process, and the subjects history of previous vaccination.

• #8 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  The VE of current influenza vaccines is suboptimal, having been estimated as 40% to 60% when the vaccines strains are antigenically well-matched with the circulating viruses. […] VE is dependent on several factors such as the age of vaccinees, the match between the strain included in the vaccine composition and the circulating virus, egg-adaptations occurring during the production process, and the subjects history of previous vaccination as recently supposed. […] Vaccine impact is referred to as the reduction in disease incidence where some subjects have received vaccination. […] Vaccination is therefore strongly recommended for the elderly, in order to prevent the disease and its related complications. […] VE in the elderly has been evaluated in several influenza seasons from 20102011 to 20192020, and several studies have suggested that it exerts an overall protective effect even in elderly people with cardiovascular and/or respiratory diseases and those over 75 years old.

• #9 2024-2025 Flu Vaccine Effectiveness: What Do We Know?

  https://www.flu.com/Articles/2024/2024-2025-Flu-Vaccine-Effectiveness

  With the flu season now well underway in the Northern Hemisphere, you might be wondering about the effectiveness of this seasons flu vaccine. […] According to the newly released CDC report, vaccine effectiveness against any influenza in children and adolescents was between 32% and 60% in outpatient settings, and between 63% and 78% against influenza-associated hospitalization. For adults aged 18 and older, vaccine effectiveness was 36% to 54% in outpatient settings and 41% to 55% against hospitalization. […] Based on last year’s Southern Hemisphere data, experts estimated that the Northern Hemisphere flu vaccine would reduce the risk of hospitalization due to the flu by around 35%, once all data is collected for the 20242025 flu season. […] Flu vaccine effectiveness for influenza A(H3N2) strains tends to be lower than for Influenza A(H1N1) and Influenza B viruses.

• #10 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  A more challenging issue is the antigenic drift of the A strains, especially for H3N2 viruses, which can result in a complete lack of protection in specific seasons. […] This issue can be exacerbated by the conventional influenza vaccine production technology of embryonated hens eggs which carries the risk of antigenically mis-matched vaccine virus by the introduction of egg-adapted mutations. […] Nevertheless, even these vaccines may face the limitations of potential mismatches between the circulating strains and the WHO-recommended vaccine strains caused by antigenic drift, especially during an influenza season. […] Therefore, such studies most likely cannot be performed by individual vaccine producers but may need the intensive support of all stakeholders involved in the timely production of seasonal influenza vaccines, i.e., the WHO, International Institutions, the scientific community, and, last, but not least, Regulatory Authorities worldwide.

• #11 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  A more challenging issue is the antigenic drift of the A strains, especially for H3N2 viruses, which can result in a complete lack of protection in specific seasons. […] This issue can be exacerbated by the conventional influenza vaccine production technology of embryonated hens eggs which carries the risk of antigenically mis-matched vaccine virus by the introduction of egg-adapted mutations. […] Nevertheless, even these vaccines may face the limitations of potential mismatches between the circulating strains and the WHO-recommended vaccine strains caused by antigenic drift, especially during an influenza season. […] Therefore, such studies most likely cannot be performed by individual vaccine producers but may need the intensive support of all stakeholders involved in the timely production of seasonal influenza vaccines, i.e., the WHO, International Institutions, the scientific community, and, last, but not least, Regulatory Authorities worldwide.

• #12 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Overall, the consensus is that vaccination is protective in children, though age-related differences were found in some cases and the lowest protection was observed against H3N2. […] Overall, it is commonly accepted in the scientific and medical communities that vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to (high-) risk groups such as young children, elderly adults, persons with chronic medical conditions, and immunocompromised persons. […] However, the outcome of such effectiveness studies is very dependent on influenza virus-specific parameters, mainly the antigenic drift, especially of the A-strains or the differently circulating B-strains of the two divergent lineages B-Victoria and B-Yamagata.

• #13 2024-2025 Flu Vaccine Effectiveness: What Do We Know?

  https://www.flu.com/Articles/2024/2024-2025-Flu-Vaccine-Effectiveness

  Even a vaccine with lower effectiveness can mean the difference between a mild illness and a hospital stay. Studies have shown flu vaccination lowers the risk of flu-related hospitalization by 41% in young children and 82% in adults. Vaccinated individuals who still get sick with flu are also less likely to be admitted to the ICU.

• #14 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  The VE of current influenza vaccines is suboptimal, having been estimated as 40% to 60% when the vaccines strains are antigenically well-matched with the circulating viruses. […] VE is dependent on several factors such as the age of vaccinees, the match between the strain included in the vaccine composition and the circulating virus, egg-adaptations occurring during the production process, and the subjects history of previous vaccination as recently supposed. […] Vaccine impact is referred to as the reduction in disease incidence where some subjects have received vaccination. […] Vaccination is therefore strongly recommended for the elderly, in order to prevent the disease and its related complications. […] VE in the elderly has been evaluated in several influenza seasons from 20102011 to 20192020, and several studies have suggested that it exerts an overall protective effect even in elderly people with cardiovascular and/or respiratory diseases and those over 75 years old.

• #15 Influenza Vaccination and Mortality: Differentiating Vaccine Effects From Bias

  https://pmc.ncbi.nlm.nih.gov/articles/PMC2728831/

  Our VE estimate of 4.6% implies that in the absence of flu shots, there would have been 342 flu-season deaths (326/0.954 = 342) in vaccinees. […] Thus, vaccination prevented approximately 16 flu-season deaths per 100,000 person-years (342 326 = 16) in the Kaiser Permanente population, which amounted to approximately 25 deaths prevented per 100,000 people vaccinated. […] Our findings suggest that had none of the elderly been vaccinated, excess mortality during flu season would have averaged about 9.8%. […] We found that flu shots reduced all-cause mortality among elderly Kaiser Permanente members by 4.6% during 9 laboratory-defined flu seasons in Northern California. […] Our estimate of 4.6% vaccine effectiveness against all-cause mortality during flu season may seem disappointing, it amounts to approximately 47% of a plausible target: the rise in mortality that would have occurred during flu season had none of the elderly been vaccinated.

• #16 2024-2025 Flu Vaccine Effectiveness: What Do We Know?

  https://www.flu.com/Articles/2024/2024-2025-Flu-Vaccine-Effectiveness

  Even a vaccine with lower effectiveness can mean the difference between a mild illness and a hospital stay. Studies have shown flu vaccination lowers the risk of flu-related hospitalization by 41% in young children and 82% in adults. Vaccinated individuals who still get sick with flu are also less likely to be admitted to the ICU.

• #17 Efficacy of FLU-v, a broad-spectrum influenza vaccine, in a randomized phase IIb human influenza challenge study | npj Vaccines

  https://www.nature.com/articles/s41541-020-0174-9

  In this study single-dose adjuvanted FLU-v was safe and efficacious in that it induced a statistically significant reduction in the number of participants positive for MMID compared to placebo. These data demonstrate the efficacy of this broad-spectrum, universal vaccine candidate and do so in a healthy volunteer human challenge model. […] Single-dose adjuvanted FLU-v demonstrated a statistically significant reduction in the number of individuals who developed at least two symptoms of influenza, regardless of shedding. FLU-v was able to offer protection that reduced the severity of illness, even in this very healthy population. […] The primary endpoint of MMID is a strict definition of influenza infection and in a typical human population exposed to influenza naturally a broader spectrum of illness would occur, therefore making it likely that the effect of this vaccine on disease severity may be even greater than observed here.

• #18 No, really, get a flu shot: Frequently asked questions about the flu vaccine – UChicago Medicine

  https://www.uchicagomedicine.org/forefront/prevention-and-screening-articles/2024/october/frequently-asked-questions-about-the-flu-vaccine

  Research shows that getting the flu vaccine can reduce influenza illnesses by 40% to 60%. […] Unfortunately, we dont yet have a universal flu vaccine that would protect us from all influenza for all time. […] Yes, its true that the flu vaccine wont always work in everyone who gets it. A persons immune history has a lot to do with their response to the vaccine. Also, the effectiveness of the vaccine varies each year. However, even when the shot isnt as effective, it can help minimize how sick people become if they are infected.

• #19 Uptake, safety and effectiveness of inactivated influenza vaccine in inflammatory bowel disease: a UK-wide study | BMJ Open Gastroenterology

  https://bmjopengastro.bmj.com/content/11/1/e001370

  Objective To investigate (1) the UK-wide inactivated influenza vaccine (IIV) uptake in adults with inflammatory bowel disease (IBD), (2) the association between vaccination against influenza and IBD flare and (3) the effectiveness of IIV in preventing morbidity and mortality. […] The uptake of influenza vaccine was low in people with IBD, and the majority were not vaccinated before influenza virus circulated in the community. Vaccination with the IIV was not associated with IBD flare. These findings add to the evidence to promote vaccination against influenza in people with IBD. […] Seasonal influenza vaccination was not associated with IBD flare. […] These findings add to the evidence to promote vaccination in people with IBD. […] Vaccination with the IIV was not associated with an increased risk of IBD flare in this study. This is consistent with uncontrolled data from previous studies.

• #20 Uptake, safety and effectiveness of inactivated influenza vaccine in inflammatory bowel disease: a UK-wide study | BMJ Open Gastroenterology

  https://bmjopengastro.bmj.com/content/11/1/e001370

  Vaccination against seasonal influenza was not associated with IBD flares 90 days post-vaccination. […] In conclusion, this study provided the first UK-wide population-based evidence that the uptake of vaccination against influenza is low in people with IBD and that vaccination does not occur in time before the virus circulates in the community in this population. Vaccination against influenza was not associated with IBD flare. These data should be used to promote vaccination in IBD population.

• #21 Efficacy of FLU-v, a broad-spectrum influenza vaccine, in a randomized phase IIb human influenza challenge study | npj Vaccines

  https://www.nature.com/articles/s41541-020-0174-9

  FLU-v, developed by PepTcell (SEEK), is a peptide vaccine aiming to provide a broadly protective cellular immune response against influenza A and B. A randomized, double-blind, placebo-controlled, single-center, phase IIb efficacy and safety trial was conducted. The primary objective of the study was to identify a reduction in mild to moderate influenza disease (MMID) defined as the presence of viral shedding and clinical influenza symptoms. Single-dose adjuvanted FLU-v recipients (n=40) were significantly less likely to develop MMID after challenge vs placebo (n=42) (32.5% vs 54.8% p=0.035). FLU-v should continue to be evaluated and cellular immunity explored further as a possible important correlate of protection against influenza. […] The objective of this study was to test the efficacy of adjuvanted FLU-v in a healthy volunteer H1N1 challenge model developed by the LID Clinical Studies Unit at the National Institute of Allergy and Infectious Diseases (NIAID).

• #22 Efficacy of FLU-v, a broad-spectrum influenza vaccine, in a randomized phase IIb human influenza challenge study | npj Vaccines

  https://www.nature.com/articles/s41541-020-0174-9

  FLU-v, developed by PepTcell (SEEK), is a peptide vaccine aiming to provide a broadly protective cellular immune response against influenza A and B. A randomized, double-blind, placebo-controlled, single-center, phase IIb efficacy and safety trial was conducted. The primary objective of the study was to identify a reduction in mild to moderate influenza disease (MMID) defined as the presence of viral shedding and clinical influenza symptoms. Single-dose adjuvanted FLU-v recipients (n=40) were significantly less likely to develop MMID after challenge vs placebo (n=42) (32.5% vs 54.8% p=0.035). FLU-v should continue to be evaluated and cellular immunity explored further as a possible important correlate of protection against influenza. […] The objective of this study was to test the efficacy of adjuvanted FLU-v in a healthy volunteer H1N1 challenge model developed by the LID Clinical Studies Unit at the National Institute of Allergy and Infectious Diseases (NIAID).

• #23 Efficacy of FLU-v, a broad-spectrum influenza vaccine, in a randomized phase IIb human influenza challenge study | npj Vaccines

  https://www.nature.com/articles/s41541-020-0174-9

  In this study single-dose adjuvanted FLU-v was safe and efficacious in that it induced a statistically significant reduction in the number of participants positive for MMID compared to placebo. These data demonstrate the efficacy of this broad-spectrum, universal vaccine candidate and do so in a healthy volunteer human challenge model. […] Single-dose adjuvanted FLU-v demonstrated a statistically significant reduction in the number of individuals who developed at least two symptoms of influenza, regardless of shedding. FLU-v was able to offer protection that reduced the severity of illness, even in this very healthy population. […] The primary endpoint of MMID is a strict definition of influenza infection and in a typical human population exposed to influenza naturally a broader spectrum of illness would occur, therefore making it likely that the effect of this vaccine on disease severity may be even greater than observed here.

• #24 Efficacy of FLU-v, a broad-spectrum influenza vaccine, in a randomized phase IIb human influenza challenge study | npj Vaccines

  https://www.nature.com/articles/s41541-020-0174-9

  The efficacy of FLU-v in this wild-type human influenza challenge study along with the supporting data from previous trials in the field should be further examined in larger field trials where efficacy of FLU-v will be evaluated against a broader set of influenza strains and wider spectrum of disease to determine if these results will be broadly applicable.

• #25 Influenza: The Disease & Vaccines | Children’s Hospital of Philadelphia

  https://www.chop.edu/vaccine-education-center/vaccine-details/influenza-vaccine

  The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months of age and older receive the influenza vaccine each year. […] Most people should receive the influenza vaccine in the fall, preferably September or October. […] The influenza vaccine is unusual in that most years a different vaccine is made. […] The influenza vaccine can cause mild side effects. On the other hand, influenza typically hospitalizes and kills more people in this country than any other vaccine-preventable disease about 200,000 hospitalizations and thousands to tens of thousands of deaths occur every year. Therefore, the benefits of the influenza vaccine clearly outweigh its risks.

• #26 Influenza: The Disease & Vaccines | Children’s Hospital of Philadelphia

  https://www.chop.edu/vaccine-education-center/vaccine-details/influenza-vaccine

  The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months of age and older receive the influenza vaccine each year. […] Most people should receive the influenza vaccine in the fall, preferably September or October. […] The influenza vaccine is unusual in that most years a different vaccine is made. […] The influenza vaccine can cause mild side effects. On the other hand, influenza typically hospitalizes and kills more people in this country than any other vaccine-preventable disease about 200,000 hospitalizations and thousands to tens of thousands of deaths occur every year. Therefore, the benefits of the influenza vaccine clearly outweigh its risks.

• #27 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  Interim 20242025 seasonal influenza VE estimates were derived from four U.S. VE networks. Among children and adolescents, VE was 32%, 59%, and 60% in outpatient settings (three networks) and 63% and 78% against influenza-associated hospitalization (two networks). Among adults, VE was 36% and 54% in outpatient settings (two networks) and 41% and 55% against influenza-associated hospitalization (two networks). […] Vaccination with the 20242025 influenza vaccine reduced the risk for influenza-associated outpatient visits and hospitalization. These findings support recommendations that all eligible persons aged 6 months should receive an annual influenza vaccination. Vaccination should be offered as long as influenza viruses are circulating. […] Preliminary estimates indicate that receipt of the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and influenza-associated hospitalization.

• #28 Immunizations: Influenza Vaccine Data | Wisconsin Department of Health Services

  https://www.dhs.wisconsin.gov/immunization/influenza.htm

  Influenza, also called the flu, affects people differently and can lead to serious complications or even death. The best way to protect yourself and your community from the flu is to get a vaccine every fall. Flu vaccines are safe and effective at protecting people against illness, hospitalization, and even death. […] Vaccination coverage: An estimated percentage of the whole population who have received a flu vaccine. This helps us understand how well communities are protected from flu. It also helps us see which areas and groups are less protected against flu. […] The map above can be used to help public health officials identify neighborhoods and communities with low influenza vaccination coverage. Public health officials can target messaging and increase access to influenza vaccines to areas with low coverage and low SVI scores.

• #29 CDC Seasonal Flu Vaccine Effectiveness Studies | Flu Vaccines Work | CDC

  https://www.cdc.gov/flu-vaccines-work/php/effectiveness-studies/index.html

  CDC conducts studies each flu season to help determine how well flu vaccines are working. […] The results of vaccine effectiveness studies can vary based on the study design, the outcome(s) measured, the population studied, and the season studied. […] Over the past few years, CDC has conducted VE studies using multiple vaccine effectiveness networks. […] The overall, adjusted vaccine effectiveness estimates for flu seasons from 2004-2024 are noted in the chart below. […] The vaccine effectiveness estimates included in the chart and tables below are vaccine effectiveness estimates from the U.S. Flu VE Network. […] Adjusted vaccine effectiveness estimates for influenza seasons from 2004-2024. […] Vaccine effectiveness (VE) estimates for the 2008-2009 flu season have not been published. […] Overall VE was calculated for this table to be consistent with what has been reported historically and is available for comparison with historical estimates.

• #30 Effectiveness of the Influenza Vaccine During the 2024-2025 Respiratory Viral Season | medRxiv

  https://www.medrxiv.org/content/10.1101/2025.01.30.25321421v3

  The purpose of this study was to evaluate the effectiveness of the influenza vaccine during the 2024-2025 respiratory viral season. […] The cumulative incidence of influenza was similar for the vaccinated and unvaccinated states early, but over the course of the study the cumulative incidence of influenza increased more rapidly among the vaccinated than the unvaccinated. […] In an analysis adjusted for age, sex, clinical nursing job, and employment location, the risk of influenza was significantly higher for the vaccinated compared to the unvaccinated state (HR, 1.27; 95% C.I., 1.07 1.51; P = 0.007), yielding a calculated vaccine effectiveness of 26.9% (95% C.I., 55.0 to 6.6%). […] This study found that influenza vaccination of working-aged adults was associated with a higher risk of influenza during the 2024-2025 respiratory viral season, suggesting that the vaccine has not been effective in preventing influenza this season. […] Among 53402 working-aged Cleveland Clinic employees, we were unable to find that the influenza vaccine has been effective in preventing infection during the 2024-2025 respiratory viral season.

• #31 No, really, get a flu shot: Frequently asked questions about the flu vaccine – UChicago Medicine

  https://www.uchicagomedicine.org/forefront/prevention-and-screening-articles/2024/october/frequently-asked-questions-about-the-flu-vaccine

  Research shows that getting the flu vaccine can reduce influenza illnesses by 40% to 60%. […] Unfortunately, we dont yet have a universal flu vaccine that would protect us from all influenza for all time. […] Yes, its true that the flu vaccine wont always work in everyone who gets it. A persons immune history has a lot to do with their response to the vaccine. Also, the effectiveness of the vaccine varies each year. However, even when the shot isnt as effective, it can help minimize how sick people become if they are infected.

• #32 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Influenza is a vaccine preventable disease and vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to risk groups. […] The effectiveness of current influenza is suboptimal, being estimated as 40% to 60% when the vaccines strains are antigenically well-matched with the circulating viruses. […] Overall, influenza vaccines are effective against morbidity and mortality in all age and risk groups, especially in young children and older adults. […] However, the effectiveness is dependent on several factors such as the age of vaccinees, the match between the strain included in the vaccine composition and the circulating virus, egg-adaptations occurring during the production process, and the subjects history of previous vaccination.

• #33 No, really, get a flu shot: Frequently asked questions about the flu vaccine – UChicago Medicine

  https://www.uchicagomedicine.org/forefront/prevention-and-screening-articles/2024/october/frequently-asked-questions-about-the-flu-vaccine

  Research shows that getting the flu vaccine can reduce influenza illnesses by 40% to 60%. […] Unfortunately, we dont yet have a universal flu vaccine that would protect us from all influenza for all time. […] Yes, its true that the flu vaccine wont always work in everyone who gets it. A persons immune history has a lot to do with their response to the vaccine. Also, the effectiveness of the vaccine varies each year. However, even when the shot isnt as effective, it can help minimize how sick people become if they are infected.

• #34 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  Interim 20242025 seasonal influenza VE estimates were derived from four U.S. VE networks. Among children and adolescents, VE was 32%, 59%, and 60% in outpatient settings (three networks) and 63% and 78% against influenza-associated hospitalization (two networks). Among adults, VE was 36% and 54% in outpatient settings (two networks) and 41% and 55% against influenza-associated hospitalization (two networks). […] Vaccination with the 20242025 influenza vaccine reduced the risk for influenza-associated outpatient visits and hospitalization. These findings support recommendations that all eligible persons aged 6 months should receive an annual influenza vaccination. Vaccination should be offered as long as influenza viruses are circulating. […] Preliminary estimates indicate that receipt of the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and influenza-associated hospitalization.

• #35 Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025 | MMWR

  https://www.cdc.gov/mmwr/volumes/74/wr/mm7406a2.htm

  These interim estimates of 202425 VE indicate that influenza vaccination was effective in preventing medically attended influenza-associated illness in children, adolescents, and adults in the United States. Among children and adolescents, VE against medically attended influenza ranged from 32% to 60% in outpatient settings and from 63% to 78% against influenza-associated hospitalization. Among adults, VE against medically attended influenza was 36% and 54% in two outpatient settings and 41% and 55% against influenza-associated hospitalization. […] Findings in this report show that vaccination with the 20242025 influenza vaccine reduced the likelihood of medically attended influenza and support CDCs recommendation that all persons aged 6 months be vaccinated against influenza. These findings also support the strong protective effect influenza vaccination has against influenza-associated hospitalization, demonstrating the importance of vaccination to reduce more severe influenza-associated complications.

• #36 Influenza Viruses and Vaccines: The Role of Vaccine Effectiveness Studies for Evaluation of the Benefits of Influenza Vaccines

  https://pmc.ncbi.nlm.nih.gov/articles/PMC9143275/

  Overall, the consensus is that vaccination is protective in children, though age-related differences were found in some cases and the lowest protection was observed against H3N2. […] Overall, it is commonly accepted in the scientific and medical communities that vaccination remains the most effective method of controlling the morbidity and mortality of seasonal influenza, especially with respect to (high-) risk groups such as young children, elderly adults, persons with chronic medical conditions, and immunocompromised persons. […] However, the outcome of such effectiveness studies is very dependent on influenza virus-specific parameters, mainly the antigenic drift, especially of the A-strains or the differently circulating B-strains of the two divergent lineages B-Victoria and B-Yamagata.

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