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Does This Year’s Flu Vaccine Work?

Today the CDC announced that preliminary data from early flu virus surveillance has shown that about half of the flu present in the US currently is not directly covered by this year’s vaccine. What does this mean?

– The types of flu covered by the annual vaccine are chosen 6 months before flu season, based on mapping flu strains around the world. In a typical year, about 70% of the strains of flu present are successfully anticipated by that year’s vaccine. Once the predominant strains are found, vaccine manufacturing begins, producing millions of doses in time for flu season.

Over that intervening time period, the flu can mutate – like this year, leading to prevalence of strains not perfectly covered by the vaccine. The good news is that there can be some cross-reactivity between the protective antibodies your body makes from the current vaccine and the mutated flu virus around. So vaccination remains a vital part of avoiding getting sick: half the strains are well covered by this year’s vaccine, and the other half are partially covered.

– Treatment for flu symptoms should be aggressive and early, especially for those with risks factors for a more severe course. If you think you have the flu, you should contact your doctor immediately. The greatest benefits from anti-flu medications such as Tamiflu are obtained if medication is started with 48 hours of the onset of symptoms.

According to the CDC: “Clinical trials and observational data show that early antiviral treatment can:

  1. shorten the duration of fever and illness symptoms;

  2. reduce the risk of complications from influenza (e.g., otitis media in young children and pneumonia requiring antibiotics in adults); and

  3. reduce the risk of death among hospitalized patients.”

Those at highest risk for complications from the flu include:

* children aged younger than 2 years;

* adults aged 65 years and older;

* persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), and metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury);

* persons with immunosuppression, including that caused by medications or by HIV infection;

* women who are pregnant or postpartum (within 2 weeks after delivery);

* persons aged younger than 19 years who are receiving long-term aspirin therapy;

* American Indians/Alaska Natives;

* persons who are morbidly obese (i.e., body-mass index is equal to or greater than 40); and

* residents of nursing homes and other chronic-care facilities.

To reduce the substantial burden of influenza in the United States, the CDC continues to recommend a three-pronged approach:

(1) influenza vaccination. The influenza vaccine contains three or four influenza viruses depending on the influenza vaccine—an influenza A (H1N1) virus, an influenza A (H3N2) virus, and one or two influenza B viruses. Therefore, even if vaccine effectiveness is reduced against drifted circulating viruses, the vaccine will protect against non-drifted circulating vaccine viruses. Further, there is evidence to suggest that vaccination may make illness milder and prevent influenza-related complications.

(2) use of neuraminidase inhibitor medications when indicated for treatment or prevention. Antiviral treatment with oseltamivir or zanamivir is recommended as early as possible for any patient with confirmed or suspected influenza who: is hospitalized; has severe, complicated, or progressive illness; or is at higher risk for influenza complications. Antiviral chemoprophylaxis should be used for prevention of influenza when indicated.

(3) use of other preventive health practices that may help decrease the spread of influenza, including respiratory hygiene, cough etiquette, social distancing (e.g., staying home from work and school when ill, staying away from people who are sick) and hand washing.

For more information, here is a link to the relevant CDC site:

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