influenza, human

Incidence, co-occurrence, and evolution of long-COVID features: A 6-month retrospective cohort study of 273,618 survivors of COVID-19

Bethie Seay — Tue, 05 Oct 2021 05:00:00 +0000

Date Added:

October 5, 2021

Journal/Publication:

PLOS Medicine

Publication Date:

September 28, 2021

Issue:

Volume:

Type:

Clinical Research Results

DOI (1):

10.1371/journal.pmed.1003773

An assessment of the epidemiology and characteristics of long COVID syndrome from nearly 275,000 linked electronic records.

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Background
Long-COVID refers to a variety of symptoms affecting different organs reported by people following Coronavirus Disease 2019 (COVID-19) infection. To date, there have been no robust estimates of the incidence and co-occurrence of long-COVID features, their relationship to age, sex, or severity of infection, and the extent to which they are specific to COVID-19. The aim of this study is to address these issues.

Methods and findings
We conducted a retrospective cohort study based on linked electronic health records (EHRs) data from 81 million patients including 273,618 COVID-19 survivors. The incidence and co-occurrence within 6 months and in the 3 to 6 months after COVID-19 diagnosis were calculated for 9 core features of long-COVID (breathing difficulties/breathlessness, fatigue/malaise, chest/throat pain, headache, abdominal symptoms, myalgia, other pain, cognitive symptoms, and anxiety/depression). Their co-occurrence network was also analyzed. Comparison with a propensity score–matched cohort of patients diagnosed with influenza during the same time period was achieved using Kaplan–Meier analysis and the Cox proportional hazard model. The incidence of atopic dermatitis was used as a negative control.

Among COVID-19 survivors (mean [SD] age: 46.3 [19.8], 55.6% female), 57.00% had one or more long-COVID feature recorded during the whole 6-month period (i.e., including the acute phase), and 36.55% between 3 and 6 months. The incidence of each feature was: abnormal breathing (18.71% in the 1- to 180-day period; 7.94% in the 90- to180-day period), fatigue/malaise (12.82%; 5.87%), chest/throat pain (12.60%; 5.71%), headache (8.67%; 4.63%), other pain (11.60%; 7.19%), abdominal symptoms (15.58%; 8.29%), myalgia (3.24%; 1.54%), cognitive symptoms (7.88%; 3.95%), and anxiety/depression (22.82%; 15.49%). All 9 features were more frequently reported after COVID-19 than after influenza (with an overall excess incidence of 16.60% and hazard ratios between 1.44 and 2.04, all p < 0.001), co-occurred more commonly, and formed a more interconnected network. Significant differences in incidence and co-occurrence were associated with sex, age, and illness severity. Besides the limitations inherent to EHR data, limitations of this study include that (i) the findings do not generalize to patients who have had COVID-19 but were not diagnosed, nor to patients who do not seek or receive medical attention when experiencing symptoms of long-COVID; (ii) the findings say nothing about the persistence of the clinical features; and (iii) the difference between cohorts might be affected by one cohort seeking or receiving more medical attention for their symptoms.

Conclusions
Long-COVID clinical features occurred and co-occurred frequently and showed some specificity to COVID-19, though they were also observed after influenza. Different long-COVID clinical profiles were observed based on demographics and illness severity.

Author summary
Why was this study done?
Long-COVID has been described in recent studies. But we do not know the risk of developing features of this condition and how it is affected by factors such as age, sex, or severity of infection.
We do not know if the risk of having features of long-COVID is more likely after Coronavirus Disease 2019 (COVID-19) than after influenza.
We do not know about the extent to which different features of long-COVID co-occur.
What did the researchers do and find?
This research used data from electronic health records of 273,618 patients diagnosed with COVID-19 and estimated the risk of having long-COVID features in the 6 months after a diagnosis of COVID-19. It compared the risk of long-COVID features in different groups within the population and also compared the risk to that after influenza.
The research found that over 1 in 3 patients had one or more features of long-COVID recorded between 3 and 6 months after a diagnosis of COVID-19. This was significantly higher than after influenza.
For 2 in 5 of the patients who had long-COVID features in the 3- to 6-month period, they had no record of any such feature in the previous 3 months.
The risk of long-COVID features was higher in patients who had more severe COVID-19 illness, and slightly higher among females and young adults. White and non-white patients were equally affected.
What do these findings mean?
Knowing the risk of long-COVID features helps in planning the relevant healthcare service provision.
The fact that the risk is higher after COVID-19 than after influenza suggests that their origin might, in part, directly involve infection with SARS-CoV-2 and is not just a general consequence of viral infection. This might help in developing effective treatments against long-COVID.
The findings in the subgroups, and the fact that the majority of patients who have features of long-COVID in the 3- to 6-month period already had symptoms in the first 3 months, may help in identifying those at greatest risk.

Author/s:

Taquet, M., Dercon, Q., Luciano, S., Geddes, J. R., Husain, M., Harrison, P. J.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021-22 Influenza Season

Bethie Seay — Thu, 26 Aug 2021 05:00:00 +0000

Date Added:

August 26, 2021

Type:

Public Health Announcements

MeSH

Influenza A Virus, H1N1 Subtype

SARS-CoV-2

influenza, human

vaccines, inactivated

Pregnancy Trimester, Third

Inpatients

prevalence

united states food and drug administration

Centers for Disease Control and Prevention, U.S.

Intensive Care Units

Cell Culture Techniques

delivery of health care

The 2021-2022 CDC recommendations regarding administration of influenza vaccines.

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This report updates the 2020–21 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2020;69[No. RR-8]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. During the 2021–22 influenza season, the following types of vaccines are expected to be available: inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4).

The 2021–22 influenza season is expected to coincide with continued circulation of SARS-CoV-2, the virus that causes COVID-19. Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient visits, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system. Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html. Recommendations for the use of COVID-19 vaccines are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html, and additional clinical guidance is available at https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-v....

Updates described in this report reflect discussions during public meetings of ACIP that were held on October 28, 2020; February 25, 2021; and June 24, 2021. Primary updates to this report include the following six items. First, all seasonal influenza vaccines available in the United States for the 2021–22 season are expected to be quadrivalent. Second, the composition of 2021–22 U.S. influenza vaccines includes updates to the influenza A(H1N1)pdm09 and influenza A(H3N2) components. U.S.-licensed influenza vaccines will contain hemagglutinin derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture–based and recombinant vaccines), an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus, an influenza B/Washington/02/2019 (Victoria lineage)-like virus, and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Third, the approved age indication for the cell culture–based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), has been expanded from ages ≥4 years to ages ≥2 years. Fourth, discussion of administration of influenza vaccines with other vaccines includes considerations for coadministration of influenza vaccines and COVID-19 vaccines. Providers should also consult current ACIP COVID-19 vaccine recommendations and CDC guidance concerning coadministration of these vaccines with influenza vaccines. Vaccines that are given at the same time should be administered in separate anatomic sites. Fifth, guidance concerning timing of influenza vaccination now states that vaccination soon after vaccine becomes available can be considered for pregnant women in the third trimester. As previously recommended, children who need 2 doses (children aged 6 months through 8 years who have never received influenza vaccine or who have not previously received a lifetime total of ≥2 doses) should receive their first dose as soon as possible after vaccine becomes available to allow the second dose (which must be administered ≥4 weeks later) to be received by the end of October. For nonpregnant adults, vaccination in July and August should be avoided unless there is concern that later vaccination might not be possible. Sixth, contraindications and precautions to the use of ccIIV4 and RIV4 have been modified, specifically with regard to persons with a history of severe allergic reaction (e.g., anaphylaxis) to an influenza vaccine. A history of a severe allergic reaction to a previous dose of any egg-based IIV, LAIV, or RIV of any valency is a precaution to use of ccIIV4. A history of a severe allergic reaction to a previous dose of any egg-based IIV, ccIIV, or LAIV of any valency is a precaution to use of RIV4. Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient medical setting under supervision of a provider who can recognize and manage a severe allergic reaction; providers can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction. For ccIIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any ccIIV of any valency or any component of ccIIV4 is a contraindication to future use of ccIIV4. For RIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any RIV of any valency or any component of RIV4 is a contraindication to future use of RIV4.

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2021–22 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration–licensed indications. Updates and other information are available from CDC’s influenza website (https://www.cdc.gov/flu); vaccination and health care providers should check this site periodically for additional information.

Author/s:

Grohskopf, L. A., Alyanak, E., Ferdinands, J. M., Broder, K. R., Blanton, L. H., Talbot, H. K., Fry, A. M.

Routine Childhood Vaccines Given From 1 through 18 Years of Age

Brian Desmarais — Mon, 10 Aug 2020 18:25:18 +0000

Date Added:

August 10, 2020

Journal/Publication:

Mayo Clinic Proceedings

Publication Date:

August 1, 2020

Issue:

Volume:

Pages:

1780-1795

URL:

Routine Childhood Vaccines Given From 1 through 18 Years of Age

Type:

Meta-analyses, Reviews, and Guidelines

Format:

Article

DOI (1):

10.1016/j.mayocp.2020.06.004

MeSH

influenza, human

Vaccine-Preventable Diseases

Meningococcal Vaccines

Haemophilus influenzae type b

measles-mumps-rubella vaccine

Diphtheria-Tetanus-acellular Pertussis Vaccines

child

An excellent review of the recommendations, rationales, and results of childhood immunizations. James W. Mold, MD, MPH

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In addition to the vaccines due in the first year of life, the US Advisory Committee on Immunization Practices recommends that children continue to receive vaccines regularly against a variety of infectious diseases. Starting at 12 to 15 months of life, these include the two-dose measles-mumps-rubella vaccine series and the two-dose varicella vaccine series. Also in the second year of life, infants should begin the two-dose hepatitis A vaccine series and complete the Haemophilus influenzae type B vaccine series as well as the pneumococcal conjugate vaccine series. Before 19 months of life, infants should receive the third dose of the poliovirus vaccine and the fourth dose of diphtheria-tetanus-acellular pertussis (DTaP) vaccine. The final doses of poliovirus and tetanus-diphtheria-acellular pertussis vaccines are both due at 4 to 6 years of life. Before each influenza season, every child should receive the influenza vaccine. Those less than 9 years of age who previously received less than two doses need two doses a month apart. At 11 to 12 years of life, all should get two doses of the human papillomavirus vaccine, the adolescent/adult version of the tetanus-diphtheria-acellular pertussis vaccine, and begin a two-dose series of meningococcal ACWY vaccine. Each of these vaccines is due when the vaccine works to protect against both an immediate risk as well as to provide long-term protection. Each vaccine-preventable disease varies in terms of the nature of exposure, the form of the morbidity, the risk of mortality, and potential to prevent or ameliorate its harm.

Author/s:

Jacobson, RM

Oseltamivir plus usual care versus usual care for influenza-like illness in primary care: an open-label, pragmatic, randomised controlled trial

John Bayhi — Thu, 02 Jan 2020 19:26:04 +0000

Date Added:

January 2, 2020

Journal/Publication:

Lancet

Publisher:

Elsevier Inc.

Publication Date:

December 12, 2019

URL:

Oseltamivir plus usual care versus usual care for influenza-like illness in primary care: an open-label, pragmatic, randomised controlled trial

Type:

Clinical Research Results

Format:

Article

DOI (1):

10.1016/S0140-6736(19)32982-4

Keywords

PMID (1):

31839279

MeSH

Polymerase Chain Reaction

Europe

Large pragmatic clinical trial from Europe documenting impacts of treatment of influenza with Tamiflu. James W. Mold, MD, MPH

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BACKGROUND:

Antivirals are infrequently prescribed in European primary care for influenza-like illness, mostly because of perceived ineffectiveness in real world primary care and because individuals who will especially benefit have not been identified in independent trials. We aimed to determine whether adding antiviral treatment to usual primary care for patients with influenza-like illness reduces time to recovery overall and in key subgroups.

METHODS:

We did an open-label, pragmatic, adaptive, randomised controlled trial of adding oseltamivir to usual care in patients aged 1 year and older presenting with influenza-like illness in primary care. The primary endpoint was time to recovery, defined as return to usual activities, with fever, headache, and muscle ache minor or absent. The trial was designed and powered to assess oseltamivir benefit overall and in 36 prespecified subgroups defined by age, comorbidity, previous symptom duration, and symptom severity, using a Bayesian piece-wise exponential primary analysis model. The trial is registered with the ISRCTN Registry, number ISRCTN 27908921.

FINDINGS:

Between Jan 15, 2016, and April 12, 2018, we recruited 3266 participants in 15 European countries during three seasonal influenza seasons, allocated 1629 to usual care plus oseltamivir and 1637 to usual care, and ascertained the primary outcome in 1533 (94%) and 1526 (93%). 1590 (52%) of 3059 participants had PCR-confirmed influenza infection. Time to recovery was shorter in participants randomly assigned to oseltamivir (hazard ratio 1·29, 95% Bayesian credible interval [BCrI] 1·20-1·39) overall and in 30 of the 36 prespecified subgroups, with estimated hazard ratios ranging from 1·13 to 1·72. The estimated absolute mean benefit from oseltamivir was 1·02 days (95% [BCrI] 0·74-1·31) overall, and in the prespecified subgroups, ranged from 0·70 (95% BCrI 0·30-1·20) in patients younger than 12 years, with less severe symptoms, no comorbidities, and shorter previous illness duration to 3·20 (95% BCrI 1·00-5·50) in patients aged 65 years or older who had more severe illness, comorbidities, and longer previous illness duration. Regarding harms, an increased burden of vomiting or nausea was observed in the oseltamivir group.

INTERPRETATION:

Primary care patients with influenza-like illness treated with oseltamivir recovered one day sooner on average than those managed by usual care alone. Older, sicker patients with comorbidities and longer previous symptom duration recovered 2-3 days sooner.

FUNDING:

European Commission's Seventh Framework Programme.

Author/s:

Butler, CC, van der Velden, AW, Bongard, E, Saville, BR, Holmes, J, Coenen, S, Cook, J, Francis, NA, Lewis, RJ, Godycki-Cwirko, M, Llor, C, Chlabicz, S, Lionis, C, Seifert, B, Sundvall, PD, Colliers, A, Aabenhus, R, Bjerrum, L, Jonassen Harbin, N, Lindbæk M, Glinz, D, Bucher, HC, Kovacs, B, Radzeviciene Jurgute, R, Touboul Lundgren, P, Little, P, Murphy, AW, De Sutter, A, Openshaw, P, de Jong, MD, Connor, JT, Matheeussen, V, Ieven, M, Goossens, H, Verheij, TJ

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2019-20 Influenza Season

Brian Desmarais — Mon, 30 Sep 2019 13:16:17 +0000

Date Added:

September 30, 2019

Journal/Publication:

Morbidity and Mortality Weekly Report

Publication Date:

August 23, 2019

Issue:

Volume:

Pages:

1-21

URL:

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2019-20 Influenza Seaso

Type:

Public Health Announcements

Format:

Article

DOI (1):

10.15585/mmwr.rr6803a1

Keywords

Flu vaccines

vaccination recommendations

Centers for Disease Control and Prevention

MeSH

vaccines, inactivated

Hemagglutinins

Influenza A Virus, H1N1 Subtype

Influenza A Virus, H3N2 Subtype

united states food and drug administration

centers for disease control and prevention (U.S.)

Contraindications

This year’s flu vaccine recommendations from the CDC. James W. Mold, MD, MPH

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Abstract

This report updates the 2018-19 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2018;67[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2019-20 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent formulations (IIV4s). High-dose (HD-IIV3) and adjuvanted (aIIV3) inactivated influenza vaccines will be available in trivalent formulations. Recombinant (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 25, 2018; February 27, 2019; and June 27, 2019. Primary updates in this report include the following two items. First, 2019-20 U.S. trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09-like virus, an A/Kansas/14/2017 (H3N2)-like virus, and a B/Colorado/06/2017-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain HA derived from these three viruses, and a B/Phuket/3073/2013-like virus (Yamagata lineage). Second, recent labeling changes for two IIV4s, Afluria Quadrivalent and Fluzone Quadrivalent, are discussed. The age indication for Afluria Quadrivalent has been expanded from ≥5 years to ≥6 months. The dose volume for Afluria Quadrivalent is 0.25 mL for children aged 6 through 35 months and 0.5 mL for all persons aged ≥36 months (≥3 years). The dose volume for Fluzone Quadrivalent for children aged 6 through 35 months, which was previously 0.25 mL, is now either 0.25 mL or 0.5 mL. The dose volume for Fluzone Quadrivalent is 0.5 mL for all persons aged ≥36 months (≥3 years).This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2019-20 season in the United States. A brief summary of these recommendations and a Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration-licensed indications. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Author/s:

Grohskopf, L.A., Alyanak, E., Broder, K.R., Walter, E.B., Fry, A.M., Jernigan, D.B.

Association of State Laws With Influenza Vaccination of Hospital Personnel

Tracy Ashby — Mon, 22 Apr 2019 05:00:00 +0000

Date Added:

April 22, 2019

Journal/Publication:

American Journal of Preventative Medicine

Publisher:

Elsevier Inc.

Publication Date:

April 16, 2019

URL:

Association of State Laws With Influenza Vaccination of Hospital Personnel

Type:

Community-Based Research Results

Format:

Article

DOI (1):

10.1016/j.amepre.2019.01.011

Keywords

PMID (1):

31003802

MeSH

delivery of health care

State laws and facility mandates increase rates of influence vaccination of health care workers. James W. Mold, MD, MPH.

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Introduction

Healthcare personnel influenza vaccination can reduce influenza illness and patient mortality. State laws are one tool promoting healthcare personnel influenza vaccination.

Methods

A 2016 legal assessment in 50 states and Washington DC identified (1) assessment laws: mandating hospitals assess healthcare personnel influenza vaccination status; (2) offer laws: mandating hospitals offer influenza vaccination to healthcare personnel; (3) ensure laws: mandating hospitals require healthcare personnel to demonstrate proof of influenza vaccination; and (4) surgical masking laws: mandating unvaccinated healthcare personnel to wear surgical masks during influenza season. Influenza vaccination was calculated using data reported in 2016 by short-stay acute care hospitals (n=4,370) to the National Healthcare Safety Network. Hierarchical linear modeling in 2018 examined associations between reported vaccination and assessment, offer, or ensure laws at the level of facilities nested within states, among employee and non-employee healthcare personnel and among employees only.

Results

Eighteen states had one or more healthcare personnel influenza vaccination-related laws. In the absence of any state laws, facility vaccination mandates were associated with an 11–12 percentage point increase in mean vaccination coverage (p<0.0001). Facility-level mandates were estimated to increase mean influenza vaccination coverage among all healthcare personnel by 4.2 percentage points in states with assessment laws, 6.6 percentage points in states with offer laws, and 3.1 percentage points in states with ensure laws. Results were similar in analyses restricted only to employees although percentage point increases were slightly larger.

Conclusions

State laws moderate the effect of facility-level vaccination mandates and may help increase healthcare personnel influenza vaccination coverage in facilities with or without vaccination requirements.

Author/s:

Lindley, Megan C., Mu, Yi, Hoss, Aila, Pepin, Dawn, Kalayil, Elizabeth J., van Santen, Katharina L., Edwards, Jonathan R., Pollock, Daniel A.

Vaccines for preventing influenza in healthy adults

Tracy Ashby — Wed, 30 Jan 2019 06:00:00 +0000

Date Added:

January 30, 2019

Journal/Publication:

Cochrane Database of Systematic Reviews 2018

Publisher:

John Wiley and Sons

Publication Date:

February 1, 2018

Issue:

URL:

Vaccines for preventing influenza in healthy adults.

Type:

Meta-analyses, Reviews, and Guidelines

Format:

Article

DOI (1):

10.1002/14651858.CD001269.pub6

Keywords

vaccination

PMID (1):

29388196

MeSH

influenza, human

influenza vaccines

pandemics

vaccines, inactivated

pregnancy

In a typical year, in healthy adults, influenza vaccination reduces the probability of developing a flu-like illness from 21.5% to 18.1%. History of vaccination should not be used when deciding whether an adult patient has the flu.

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BACKGROUND:

The consequences of influenza in adults are mainly time off work. Vaccination of pregnant women is recommended internationally. This is an update of a review published in 2014. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

OBJECTIVES:

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS:

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE (January 1966 to 31 December 2016), Embase (1990 to 31 December 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017), as well as checking the bibliographies of retrieved articles.

SELECTION CRITERIA:

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthyindividuals aged 16 to 65 years. Previous versions of this review included observational comparative studies assessing serious and rare harms cohort and case-control studies. Due to the uncertain quality of observational (i.e. non-randomised) studies and their lack of influence on the review conclusions, we decided to update only randomised evidence. The searches for observational comparative studies are no longer updated.

DATA COLLECTION AND ANALYSIS:

Two review authors independently assessed trial quality and extracted data. We rated certainty of evidence for key outcomes (influenza, influenza-like illness (ILI), hospitalisation, and adverse effects) using GRADE.

MAIN RESULTS:

We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines. We have presented findings from 25 studies comparing inactivated parenteral influenza vaccine against placebo or do-nothing control groups as the most relevant to decision-making. The studies were conducted over single influenza seasons in North America, South America, and Europe between 1969 and 2009. We did not consider studies at high risk of bias to influence the results of our outcomes except for hospitalisation.Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vaccination to 0.9% (risk ratio (RR) 0.41, 95% confidence interval (CI) 0.36 to 0.47; 71,221 participants; moderate-certainty evidence), and they probably reduce ILI from 21.5% to 18.1% (RR 0.84, 95% CI 0.75 to 0.95; 25,795 participants; moderate-certainty evidence; 71 healthy adults need to be vaccinated to prevent one of them experiencing influenza, and 29 healthy adults need to be vaccinated to prevent one of them experiencing an ILI). The difference between the two number needed to vaccinate (NNV) values depends on the different incidence of ILI and confirmed influenza among the study populations. Vaccination may lead to a small reduction in the risk of hospitalisation in healthy adults, from 14.7% to 14.1%, but the CI is wide and does not rule out a large benefit (RR 0.96, 95% CI 0.85 to 1.08; 11,924 participants; low-certainty evidence). Vaccines may lead to little or no small reduction in days off work (-0.04 days, 95% CI -0.14 days to 0.06; low-certainty evidence). Inactivated vaccines cause an increase in fever from 1.5% to 2.3%.We identified one RCT and one controlled clinical trial assessing the effects of vaccination in pregnant women. The efficacy of inactivated vaccine containing pH1N1 against influenza was 50% (95% CI 14% to 71%) in mothers (NNV 55), and 49% (95% CI 12% to 70%) in infants up to 24 weeks (NNV 56). No data were available on efficacy against seasonal influenza during pregnancy. Evidence from observational studies showed effectiveness of influenza vaccines against ILI in pregnant women to be 24% (95% CI 11% to 36%, NNV 94), and against influenza in newborns from vaccinated women to be 41% (95% CI 6% to 63%, NNV 27).Live aerosol vaccines have an overall effectiveness corresponding to an NNV of 46. The performance of one- or two-dose whole-virion 1968 to 1969 pandemic vaccines was higher (NNV 16) against ILI and (NNV 35) against influenza. There was limited impact on hospitalisations in the 1968 to 1969 pandemic (NNV 94). The administration of both seasonal and 2009 pandemic vaccines during pregnancy had no significant effect on abortion or neonatal death, but this was based on observational data sets.

AUTHORS' CONCLUSIONS:

Healthy adults who receive inactivated parenteral influenzavaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalisations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review.Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenzavaccination and serious adverse events in the comparative studies considered in this review. Fifteen included RCTs were industry funded (29%).

Update of

Vaccines for preventing influenza in healthy adults. [Cochrane Database Syst Rev. 2014]

Author/s:

Demicheli, Vittorio, Jefferson, Tom, Ferroni, Eliana, Rivetti, Alessandro, Pietrantonj, Carlo Di

Interpretation of Rapid Influenza Diagnostic Test (RIDT) Results

Jeffrey Wilson — Mon, 07 Jan 2019 16:15:20 +0000

Date Added:

January 7, 2019

Publication Date:

January 7, 2019

URL:

Interpretation of Rapid Influenza Diagnostic Test (RIDT) Results

Type:

Clinical Decision Aids

Format:

Article

Keywords

flu

influenza

RIDT

rapid influenza diagnostic test

MeSH

influenza, human

influenza vaccines

diagnostic tests, routine

antigens, viral

This information on interpretation of rapid antigen tests for influenza was condensed from information on the CDC website.

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A number of factors can influence the results of RIDTs. The accuracy of RIDTs depends largely on the conditions under which they are used.

Author/s:

Mold, James, Centers for Disease Control and Prevention (CDC)

Influenza Antivirals: Comparison

Tracy Ashby — Sun, 06 Jan 2019 06:00:00 +0000

Date Added:

January 6, 2019

Publication Date:

January 4, 2019

Type:

Clinical Decision Aids

Format:

Article

Keywords

influenza

anti-influenza medication

MeSH

influenza, human

This is a table of information about the currently available anti-influenza meds.

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Table comparing different anti-influenza medications currently available.

Interpretation of Rapid Influenza Diagnostic Test (RIDT) Results

Tracy Ashby — Sun, 06 Jan 2019 06:00:00 +0000

Date Added:

January 6, 2019

Type:

Clinical Decision Aids

Format:

Article

Keywords

rapid influenza diagnostic test

MeSH

orthomyxoviridae infections

antigens

viral

This information on interpretation of rapid antigen tests for influenza was condensed from information on the CDC website.

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A number of factors can influence the results of RIDTs. The accuracy of Rapid Influenza Diagnostic Tests (RIDTs) depends largely on the conditions under which they are used.

Checklist to Prepare Physicians’ Offices for Pandemic Influenza

Tracy Ashby — Sat, 27 Oct 2018 05:00:00 +0000

Date Added:

October 27, 2018

Publication Date:

July 1, 2015

Type:

Meta-analyses, Reviews, and Guidelines

Format:

Article

Keywords

MeSH

This is a checklist from the AAFP listing what primary care practices should do to prepare for flu season.

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American Academy of Family Physicians Checklist to Prepare Physicians' Offices for Pandemic Influenza.

Author/s:

American Academy of Family Physicians

Influenza (The Flu)

Tracy Ashby — Fri, 05 Oct 2018 05:00:00 +0000

Date Added:

October 5, 2018

Publication Date:

March 1, 2018

Type:

Patient Education Materials

Format:

Article

Keywords

influenza

symptoms

MeSH

influenza, human

This patient information handout on influenza was copied from the CDC website and lightly reformatted.

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Influenza information handout from the CDC.

Author/s:

Centers for Disease Control and Prevention (CDC)

Prevention and Control of Seasonal Influenza with Vaccines

Jeffrey Wilson — Wed, 03 Oct 2018 17:31:30 +0000

Date Added:

October 3, 2018

Publisher:

Centers for Disease Control and Prevention

Publication Date:

August 23, 2018

URL:

2018-19 Summary of Recommendations

Type:

Public Health Announcements

Format:

Web Page

Keywords

MeSH

CDC/ACIP recommendations regarding influenza vaccination for the 2018-2019 season.

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Groups Recommended for Vaccination

Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications.
A licensed, age-appropriate influenza vaccine (IIV, RIV4, or LAIV4) should be used. Consult package information for age indications.
Emphasis should be placed on vaccination of high-risk groups and their contacts/caregivers. When vaccine supply is limited, vaccination efforts should focus on delivering vaccination to (no hierarchy implied by order listed):
- Children aged 6–59 months;
- Adults aged ≥50 years;
- Persons with chronic pulmonary (including asthma), cardiovascular (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus);
- Persons who are immunocompromised due to any cause, (including medications or HIV infection);
- Women who are or will be pregnant during the influenza season;
- Children and adolescents (aged 6 months through 18 years) receiving aspirin- or salicylate-containing medications and who might be at risk for Reye syndrome;
- Residents of nursing homes and other long-term care facilities;
- American Indians/Alaska Natives;
- Persons who are extremely obese (BMI ≥40); and
- Caregivers and contacts of those at risk:
  - Health care personnel in inpatient and outpatient care settings, medical emergency-response workers, employees of nursing home and long-term care facilities who have contact with patients or residents, and students in these professions who will have contact with patients;
  - Household contacts and caregivers of children aged ≤59 months (i.e., <5 years), particularly contacts of children aged <6 months, and adults aged ≥50 years; and
  - Household contacts and caregivers of persons with medical conditions that put them at high risk of severe complications from influenza.

Author/s:

Advisory Committee on Immunization Practices