how effective are flu tests?
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The diagnostic accuracy of influenza swabs is often overestimated by clinicians. The CDC notes that rapid influenza testing has a sensitivity ranging from approximately 50% to 70% — meaning that in up to half of influenza cases, the flu swab results will still be negative.
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Mid-season estimates suggest that the flu shot has reduced the risk of illness by around 47% in vaccinated people, according to a report from the Centers for Disease Control and Prevention (CDC) released Thursday. During the severe 2017-2018 flu season, vaccine efficacy was estimated at just 36%.
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Flu vaccines also have reduced the risk of flu hospitalization among adults age 65 and older by 54% against A(H1N1) viruses and by 31% against influenza B viruses on average (2). However, protection against influenza A(H3N2) flu viruses has been less consistent.
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If signs of infection are found, the result is "positive". The blood test is the most accurate test and can normally give reliable results from 1 month after infection. The other tests tend to be less accurate and may not give a reliable result for a longer period after exposure to the infection.
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The flu vaccine will be available as an injection or as a nasal spray. In recent years, there was concern that the nasal spray flu vaccine wasn't effective enough against certain types of flu. The nasal spray vaccine is expected to be more effective in the 2019-2020 season.
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While the general incubation period for the flu is usually between one and four days, this period can vary from person to person. The average incubation period for the flu is two days . This means that, on average, people start to develop flu symptoms about two days after coming into contact with the influenza virus.
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21 CDC Morbidity and Mortality Weekly Report, the current influenza vaccine has been 45% effective overall against 2019-2020 seasonal influenza A and B viruses. Specifically, the flu vaccine has been 50% effective against influenza B/Victoria viruses and 37% effective against influenza A(H1N1)pdm09.
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In the first three weeks after infection, the test only detects Lyme 29 to 40 percent of the time. (The test is 87 percent accurate once Lyme spreads to the neurological system, and 97 percent accurate for patients who develop Lyme arthritis).
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"Influenza vaccines are about 50 or 60 per cent effective in protecting you from hospitalization due to influenza. How good are seat belts at protecting you from dying in a car accident? About 50 per cent.
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Flu vaccination can keep you from getting sick with flu. During seasons when the flu vaccine viruses are similar to circulating flu viruses, flu vaccine has been shown to reduce the risk of having to go to the doctor with flu by 40 percent to 60 percent.
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Public Health England ( PHE ) has today (Wednesday, 18 July 2018) published data on the effectiveness of the flu vaccine in the 2017 to 2018 season. The data show that overall, flu vaccine was 15% effective in all age groups.
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After the 2009 pandemic, several U.S. studies among 2 through 17-year-olds found that the nasal spray vaccine was effective against influenza B viruses, and was similarly effective against H3N2 viruses as inactivated influenza vaccines, but was less effective than inactivated influenza vaccines against the 2009 ...
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Incubation period of influenza virus The incubation period is 1–4 days, with an average of 2 days for seasonal influenza.
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An infected person can spread the flu for five to seven days after becoming infected. The infectious period can begin 24 hours before the onset of symptoms. This means you can spread the flu without even knowing you're sick.
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A study published in the New England Journal of Medicine indicated that the high-dose vaccine was 24.2% more effective in preventing flu in adults 65 years of age and older relative to a standard-dose vaccine.
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Your doctor will conduct a physical exam, look for signs and symptoms of influenza, and possibly order a test that detects influenza viruses. During times when influenza is widespread, you may not need to be tested for influenza. Your doctor may diagnose you based on your signs and symptoms.
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Across all age groups including children, the flu vaccine prevented 52% of flu cases in 2015-16, 40% of flu cases in 2016-17, 15% of flu cases in 2017-2018 and 44% of flu cases in 2018-19 (see research by Public Health England on the effectiveness of flu vaccines in the 2015-16 season , 2016-17 season , 2017-2018 ...