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Claim
Australia is well in the middle of winter, and with cold weather comes the flu.
Last year saw the highest levels of influenza activity in Australia since the 2009 swine flu pandemic.
This year, Australians wanting to be vaccinated against influenza are are mobilized in unprecedented numbers, forcing the federal government to order 800,000 additional vaccines.
But the effectiveness of the vaccine was questioned Chris Del Mar, of Bond University, in an interview with Neil Mitchell on 3AW
"This reduces the chances of getting the flu by about 1 to 2% – it's a confirmed flu in the lab, which makes a small difference. "
the flu after a vaccination only decreased by 1 to 2%? RMIT ABC Fact Check discovers
The verdict
The statement of Professor Del Mar is misleading
The source of Professor Del Mar's statement is a systematic review of studies measuring the flu vaccine effectiveness in preventing healthy flu. adults
This study found that influenza vaccine decreased the rate of influenza infection from 2.3% to 0.9% in healthy adults.
Experts contacted by Fact Check said that if this showed an absolute decrease in infection by 1.4 percentage points, using these numbers to talk about efficiency was misleading.
Professor Del Mar reportedly spoke of the relative decline in infection,
Dr. Del Mar's own study showed that the influenza vaccine had an estimated efficacy rate of 59%, not 1% to 2%
. who has been vaccinated, the risk of contracting the flu is more than halved
This is confirmed by other studies cited by the Veterinary Handbook of the Australian Department of Health, which found rates of infection. similar efficiency.
What is the flu?
Influenza, or "flu," is a respiratory disease that causes symptoms such as fever, cough, muscle aches, headache, nasal congestion, sore throat and fatigue
causes an average of 13,500 hospitalizations and 3,000 deaths in Australia each year.
Three types of influenza affect humans – types A, B and C. Influenza A and B are responsible for most infections in humans.
classified as "strains" of which they are numerous and which are constantly changing and evolving.
According to the Australian Immunization Handbook, published by the Department of Health the peak period of influenza circulation is generally between June and September for most parts of Australia, although influenza can occur all year in the tropics.
How does the vaccine work?
New influenza vaccines are developed for each influenza season in the northern and southern hemispheres
Influenza vaccines can be either inactivated – where the virus is essentially "dead" – or live attenuated, where the virus is alive, but weakened.
All influenza vaccines currently available in Australia are inactivated
Influenza vaccines typically contain three to four influenza strains – two strains of type A and one or two strains of type B.
Different strains of influenza circulate During the flu season, a number of assumptions are required to decide which strains will be included in the vaccine.
Every year, in February and September, the World Health Organization brings together experts and influenza centers from around the world to make recommendations. composition of the next influenza vaccine.
Once the World Health Organization has made its recommendation, the Australian Committee on Influenza Vaccines meets with the Therapeutic Goods Administration to confirm which strains will be included in the Australian vaccine. Standard Influenza Vaccine, this year, there are improved flu shots available for older Australians.
These vaccines include three strains of the virus rather than the usual four, and are designed to target strains most commonly affecting the elderly.
The context of the claim
The interview of Professor Del Mar on 3AW comes a few days after a speech at the Conference of General Practitioners on the Gold Coast, where he asked if the flu vaccine was oversold. 19659006] Several media reported that, in his speech, Professor Del Mar pointed out that "seasonal flu vaccines have only reduced the rate of laboratory-confirmed influenza cases by 1 to 2 percent"
. Professor Del Mar and his co-author, Professor Peter Collignon, reiterated that influenza infections are reduced by only one percent
"[A review] found that the vaccine reduced the risk of laboratory-confirmed flu: "Although this seems to be a reduction of more than 50%, it seems less optimistic expressed in absolute terms."
"The rate of infection in adults drops from 2 to 9 1 in 1000 cases
per cent per year to 1 per cent, which could be said to be halved, but in fact only 1 per cent. "
The source of claim
The criticism cited by Professor Del Mar in The Conversation's article is part of a series of three reviews of influenza vaccine effectiveness
These reviews, which deal with influenza in healthy adults, healthy children and the elderly, come from Cochrane, an independent organization that produces systematic reviews of medical research. 19659016] The Cochrane Reviews cited by Professor Del Mar compared a number of studies estimating the effectiveness of influenza vaccine to arrive at a single overall estimate of efficacy [19659006] "The first Cochrane Review examined the effects of influenza, a vaccine in healthy adults, from 25 studies conducted in unique influenza seasons in North America, South America and Europe between 1969 and 2009" , wrote the article in The Conversation States
.The report states
that the Cochrane review found that without vaccination, 23 healthy adults would receive the flu for 1000 and that for those who had been vaccinated, nine to 1000 would have the flu.
In other words: influenza vaccines probably reduce influenza in healthy adults by 2.3% without vaccination to 0.9%. "[19659016] In their conclusions, the examinina Cochrane authors state:
"Healthy adults who receive an inactivated parenteral influenza vaccine rather than a 1% lower risk of suffering from influenza during a single influenza season (2.3% vs. 1%, moderate evidence).
The review also states:
"Inactivated parenteral vaccines probably have 59% effectiveness in preventing confirmed influenza."
What it means for the infection rate
Experts told Fact Check that the Cochrane review showed that the risk of getting the flu was halved by the vaccine
Dr. David Price, Biostatistician The University of Melbourne told Fact Check: "What these numbers mean is that for every 1,000 people, 23 would get the flu without a vaccination program, but with a vaccination program, the number of people who would catch the flu would be reduced to 9 out of 1000 "
The difference in these values, says Dr. Price, shows that for 1000 vaccinated individuals, 14 cases of influenza were avoided. [19659016] "It seems that Professor Del Mar misinterpreted this figure as the effectiveness of the vaccine, which is not the case: the effectiveness of the vaccine is currently about 59%. %, "said Dr. Price, the difference between 0.9% e t 2.3% would result in a reduction of 1.4 percentage points: considering this difference as a relative difference … we can see that the total number of cases resulting from the vaccine has decreased by more than half and seems so much more effective than saying that the vaccine reduces the flu by only one to two percent. "
Mark Chatfield, biostatistician of the University of Queensland, told Fact Check:]" With two proportions, you can talk about absolute differences or relative differences or both, he's talking about absolute differences, I think that the effectiveness of the vaccine is more often expressed as a relative difference. "
Associate Professor Chatfi eld said that the two numbers should always be given to be clear when speaking of two proportions; in this case, Professor Del Mar should have pointed out that the decline was from 2.3% to 0.9%.
"The public was probably deceived when [Professor Del Mar] gave the smallest absolute difference, rather than the biggest difference relative, without saying whether it meant absolute or relative, which comfortably added to his argument. "
The Cochrane Dr. Rob Menzies, Lecturer at the School of Public Health and Community Medicine l & # 39 UNSW also acknowledged that the exam showed the risk of getting the flu. "Using the numbers from the systematic review, the vaccine reduced the disease from 2.3% to 0.9%, which represents a reduction of about 60%. the effectiveness of 59% influenza vaccine against laboratory-confirmed influenza in healthy young adults.
Is the Cochrane Review Reliable?
The Cochrane Review revealed that 2.3% of people had Professor Allen Cheng, director of the Infection Prevention and Epidemiology Unit of Health Care at Alfred Health, explained that the Use of this figure as a baseline did not account for unconfirmed influenza infections
. all patients receive a diagnostic test after contracting an influenza infection, and the test is not completely sensitive, for example if the swab is not well taken [it may not give accurate results] ", explains the Professor Cheng
"How many people have flu symptoms? went to the GP or the hospital and had a flu test?
Professor Robert Booy, head of the clinical research team at the National Center for Immunological Research and Surveillance, told Fact Check that in the absence of diagnostic tests, the experts could only estimate five to five. 10% of the Australian population would have the flu in a given year.
He also had concerns about prejudices in Cochrane reviews.
"They are all made by the same people – the three exams all came, they always have the same prejudices," said Professor Booy.
"We are concerned that from the beginning [the Cochrane reviewers] we had a subjective, nihilistic and negative view of the vaccine."
shared by Professor Raina MacIntyre, who directs the research program in Biosecurity at the Kirby Institute, who told Fact Check:
"Despite the assertion that Cochrane journals are" independent ", they are subject to the same personal prejudices. Research Study: Cochrane reviews may show opposite results based on who is doing it.They were re-analyzed (using the same data) by one group to get completely different results from another group. "[19659078] So, what is the effectiveness of the flu shot?
Dr. Menzies tells Fact Check:
The best reference on the effectiveness of the vaccine is the Australian Immunization Handbook.
The Australian Immunization Handbook is developed by the Australian Technical Advisory Group on Immunization (ATAGI) and approved by the National Council of Health and Medical Research (NHMRC). According to the manual:
"The efficacy and effectiveness of influenza vaccines of similar composition depend primarily on the age and immunocompetence of the recipient and the degree of similarity between the viral strains present in the vaccine. vaccine and those circulating the community. "
The manual refers to a number of systematic reviews and studies of the effectiveness of influenza vaccine.
One of these studies, Influenza Vaccine Efficacy in the United States, during In the 2015-2016 season, quadrivalent vaccines (vaccines against four influenza strains) were 54% effective.
A systematic review cited in the manual revealed that trivalent vaccines (three strains) were 59% effective
Professor MacIntyre added that the potential benefits of influenza vaccine are not limited to preventing the flu itself.
"There is also evidence that influenza vaccine prevents heart attacks because influenza affects coagulation, blood and mucous membranes of the arteries through various mechanisms.
[The flu vaccine] can have a significant impact on the prevention of disease, hospitalization and death, and experts from around the world 's agree on this. "
Principal Investigator: Ellen McCutchan
FactCheck @ rmit .edu.au
Sources
- The "oversold" flu vaccine: a medical expert says Australians fight flu with masks, 3AW, June 5, 2018
- The flu vaccine : how it is made and how it works, Queensland Health, March 29, 2018
- 2018 Seasonal Influenza Vaccines, Therapeutic Goods Administration, March 27, 2018
- The Conversation, June 5, 2018
- Vaccines for Prevention influenza in healthy adults, Demicheli, V et al., February 1, 2018
- Australian Immunization Handbook, Ministry of Health, August 1, 2017
- Infl Efficacy of influenza vaccine in the United States during the 2015-2016 season, Jackson ML et al., August 10, 2017 [1 9659094] Effectiveness and Efficacy of Influenza Vaccines: A Systematic Review and Meta-Analysis, Osterholm MT et al., October 26, 2011
- Influenza Vaccination of Pregnant Women and Protection of Infants, Shabir A. et al., September 4, 2014
- Influenza vaccination during pregnancy for the prevention of confirmed influenza in infants: a systematic review and meta-analysis, Nunes MC et al., March 4, 2018
- Most people do not receive immunization , but we still need it to prevent infections, The Conversation, June 8, 2018
- Building Influenza Time Surveillance Pyramids, Australia, Craig B Dalton et al., November 2013
Topics:
vaccines and immunity,
health policy,
health,
Australia
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