Influenza and Influenza Vaccine: A Review

Abstract

Influenza is a highly contagious, deadly virus, killing nearly half a million people yearly worldwide. The classic symptoms of influenza are fever, fatigue, cough, and body aches. In the outpatient setting, diagnosis can be made by clinical presentation with optional confirmatory diagnostic testing. Antiviral medications should be initiated as soon as possible, preferably within 24 hours of initiation of symptoms. The primary preventive measure against influenza is vaccination, which is recommended for all people 6 months of age or older, including pregnant and postpartum women, unless the individual has a contraindication. Vaccination should occur at the beginning of flu season, which typically begins in October. It takes approximately 14 days after vaccination for a healthy adult to reach peak antibody protection. There are challenges associated with vaccine composition and vaccine uptake. It takes approximately 6 to 8 months to identify and predict which influenza strains to include in the upcoming season's vaccine. During this time, the influenza virus may undergo antigenic drift, that is, mutating to avoid a host immune response. Antigenic drift makes the vaccine less effective in some seasons. The influenza virus occasionally undergoes antigenic shift, in which it changes to a novel virus, creating potential for a pandemic. There are also barriers to vaccine uptake, including lack of or limited access to care and misconceptions about receiving the vaccine. Interventions that improve access to and uptake of the influenza vaccine must be initiated, targeting multiple levels, including health care policy, patients, health care systems, and the health care team. This article reviews information about influenza identification, management, and prevention.

Emergence of SARS-CoV-2 Variants in the World: How Could This Happen?

“…This has been reported for other viruses such as influenza, since seasonally, one of the hemispheres develops a variant, and later, it is transmitted to the other hemisphere [97,98]. This is also due to the RNA structure of the influenza virus, with a high mutation capacity, which is why vaccination campaigns with vaccines including new influenza variants are performed every year [99]. This has already been observed in some studies that showed these differences between the different continents.…”

Performance evaluation of the LumiraDx SARS-CoV-2 & Flu A/B Test in diagnosing COVID-19 and influenza in patients with respiratory symptoms

“…[5,6] Influenza viruses are also known to cause infectious respiratory diseases in humans and these can be mistaken for COVID-19 owing to the similarity in symptoms: cough, fever, fatigue and muscle pain. [7,8] However, unlike COVID-19, the symptoms of influenza usually arise within 1-4 days following an infection. [9] While influenza is considered to be less threatening to the public than COVID-19, with 0.29-0.65 million annual deaths globally according to the WHO, [10] it can be severe and life-threatening in children, the elderly and people suffering with other conditions.…”

“…Although influenza B is less infectious, its severity and mortality rate are comparable to those of type A. [12] As the symptoms of COVID-19 and influenza are similar, [7] there is a need for a single-swab SARS-CoV-2 and influenza A/B combination test that can distinguish between these infections. This could facilitate appropriate clinical responses from healthcare professionals to target treatment and containment effectively.…”

Protective Efficacy of Recombinant Influenza Hemagglutinin Ectodomain Fusions

“…Influenza vaccination is the preferred and most cost-effective intervention tool currently available to prevent influenza virus infection and disease. Licensed influenza vaccines include inactivated whole or split viruses, (recombinant) viral subunit, and live attenuated vaccines [ 5 ]. Seasonal influenza vaccines contain viral strains or hemagglutinins (HAs) closely related to the putative upcoming seasonal strains of influenza A viruses and influenza B viruses.…”