infectious diseases
Influenza
Prevention of Influenza
Influenza infections can largely be prevented by Annual vaccination Sometimes chemoprophylaxis (ie, with antiviral drugs) Current commercially available Influenza Vaccine protect against seasonal H3N2, pandemic H1N1 influenza A, and influenza B. A vaccine for H5N1 Prevention is indicated for all patients but is especially important for high-risk patients and health care practitioners. , influenza vaccines are modified annually to include the most prevalent strains (usually 2 strains of influenza A and 1 or 2 strains of influenza B). Sometimes slightly different vaccines are used in the northern and southern hemisphere. (See also Influenza Vaccine .) When the vaccine contains the same HA and NA as the strains in the community, vaccination decreases infections by 70 to 90% in healthy adults. In institutionalized older patients, vaccines are less effective for prevention but decrease the rate of pneumonia and death by 60 to 80%. A higher-dose formulation of the vaccine is recommended for adults > 65 years. Vaccine-induced immunity is decreased by antigenic drift and is absent if there is antigenic shift. There are 2 basic types of Influenza Vaccine : Inactivated influenza vaccine (IIV) Live-attenuated influenza vaccine (LAIV) IIVis given by IM injection. Trivalent vaccines have been superseded in the US by quadrivalent vaccines that cover an additional B virus strain. For patients ≥ 65 years, high-dose quadrivalent vaccines are also available. Adverse effects are usually limited to mild pain at the injection site; the pain lasts no more than a few days. Fever, myalgia, and other systemic effects are uncommon. Multidose vials contain thimerosal, a mercury-based preservative. Public concerns about a possible link between Thimerosal and Autism have proved unfounded; however single-dose vials, which are thimerosal-free, are available. LAIVis given intranasally at a dose of 0.1 mL in each nostril (total dose is 0.2 mL). It may be used for healthy people aged 2 to 49 years. This vaccine is not recommended for the following: High-risk patients Pregnant women Household contacts of patients with severe immunodeficiency (eg, with hematopoietic stem cell transplants) Children who are receiving long-termaspirintherapy Also, it should not be given until 48 hours after stopping drug treatment of influenza. Adverse effects associated with the vaccine are mild; rhinorrhea is the most common, and mild wheezing may occur. LAIV should not be given to children who are<5 years and have reactive airway disease (eg, known asthma, recurrent or recent wheezing episodes). LAIV was not recommended for any population in the 2016–2017 and 2017–2018 flu seasons because the vaccine's H1N1 component was not adequately effective. However, the LAIV vaccine has been reformulated, and both theCenters for Disease Control and Prevention's Advisory Committee on Immunization Practices(ACIP) andAmerican Academy of Pediatrics(AAP) have reinstated it as an acceptable vaccine. For both types of vaccines, children who are < 8 years and have not been vaccinated should be given a primary dose and a booster dose 1 month apart. A complete list of influenza vaccines for the current season is available from theCenters for Disease Control and Prevention. Annual vaccination is recommended for everyone ≥ 6 months who do not have a contraindication. Influenza vaccine is given annually to maintain antibody titers and allow vaccine modification to compensate for antigenic drift. Vaccine is best given in the fall, so that antibody titers will be high during the winter influenza season (between November and March in the US). Influenza vaccine can be given at the same time as COVID-19 vaccination . Vaccination (both IIV and LAIV) should be avoided in people who Previously had a severe reaction to influenza vaccine Developed Guillain-Barré Syndrome (GBS) (GBS) within 6 weeks of a previous influenza vaccination (it is not known whether influenza vaccination increases risk of recurrent GBS in patients who have previously had GBS that was not related to influenza vaccination) Have had GBS in the previous 6 weeks, regardless of cause Are<6 months old Any of the influenza vaccines can be given to patients with a history of egg allergy, except to patients who have had a severe allergic reaction to a previous influenza vaccination, which is a contraindication to receiving the vaccine. If patients have had an allergic reaction more severe than just hives (eg, angioedema, respiratory distress, recurrent emesis), they may be given the vaccine, provided that it is given in an inpatient or outpatient medical setting and supervised by a clinician who is able to recognize and manage severe allergic reactions. Also, egg-free vaccines—a recombinant IIV for adults and a cell-culture produced IIV for people > 4 years—are available. Although vaccination is the preferred method of prevention, antiviral drugs are also effective. Preexposure prophylactic antiviral drugscan be considered during an epidemic for patients Who have been vaccinated only within the previous 2 weeks For whom vaccination is contraindicated Who are immunocompromised and thus may not respond to vaccination Antiviral drugs do not impair development of immunity from inactivated vaccine. They can be stopped 2 weeks after vaccination. If vaccine cannot be given, antiviral drugs are continued for the duration of the epidemic. are typically indicated for potentially exposed people when clusters of cases occur in a closed environment (eg, nursing home, hospital unit). These drugs may also be given to household contacts or other exposed people at High-risk groups . Resistance patterns may affect drug choice, but typically 