In the second of two blogs from public health doctors on preventing influenza (‘flu), Emma Plugge takes a look at some of the Cochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. on preventing influenza through vaccination.
“Never since the Black Death has such a plague swept over the face of the world [and] never, perhaps, has a plague been more stoically accepted.”
The Times, December 1918, quoted in ‘Spanish influenza redux: revisiting the mother of all pandemics’. Mark Honigsbaum. Lancet. 2018.
When we think of an infectious disease that’s going to wipe out the The group of people being studied. Populations may be defined by any characteristics e.g. where they live, age group, certain diseases., what springs to mind? Ebola? Monkey pox? An extra-terrestrial organism brought by space debris? And we do think of such things – well, it’s certainly a subject that Hollywood likes to visit frequently. Films such as ‘Contagion’, ‘Doomsday’ and ‘Outbreak’ are but a few in a long list of disaster movies where a virus wipes out most of the population, leaving a few plucky souls to find a cure and tend to the sick. The heroes and the plots may vary but what they all have in common is that the dreaded virus is never influenza. Influenza, ‘flu’, it would seem, is far too mundane…
But let’s travel back 100 years ago (almost exactly) and the ‘Spanish flu’ was sweeping across the world, killing at least 50 million people, a number hard to comprehend. This disease killed three times as many people than the First World War which was drawing to a close as the flu pandemic began. So whilst we mark the centenary of the end of this terrible war, let us not forget influenza, nor accept it, however ‘stoically’.
Influenza can be prevented
There are measures we can all take such as good respiratory and hand hygiene practices, encapsulated in the NHS ‘catch it, bin it, kill it’ campaign. Vaccination is also important. In yesterday’s blog on influenza vaccines, David Roberts has highlighted the issues with trying to develop the most effective vaccines – it is problematic. This highlights the importance of a series of recent Cochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. that has carefully examined and set out the evidence for influenza vaccination for a range of population subgroups. It is very important that we know how effective influenza vaccination is and what the adverse effects are when millions of doses are given in the UK each year.
Across the UK, flu vaccination is recommended each year for all those aged 65 years or over (‘older adults’) and for pregnant women and Cochrane Reviews have examined The ability of an intervention (for example a drug, surgery, or exercise) to produce a desired effect, such as reduce symptoms. in both these groups. A review looking at vaccination in older adults identified eight Randomization is the process of randomly dividing into groups the people taking part in a trial. One group (the intervention group) will be given the intervention being tested (for example a drug, surgery, or exercise) and compared with a group which does not receive the intervention (the control group). A trial in which a group (the ‘intervention group’) is given a intervention being tested (for example a drug, surgery, or exercise) is compared with a group which does not receive the intervention (the ‘control group’). (RCTs) with over 5000 participants and found that older adults receiving the influenza vaccine may experience less influenza over a single season compared with An intervention that appears to be the same as that which is being assessed but does not have the active component. For example, a placebo could be a tablet made of sugar, compared with a tablet containing a medicine., from 6% to 2.4%. However the evidence was considered to be low certainty because of ambiguity over the diagnosis of influenza. Similarly the evidence relating to complications was ‘of poor quality, insufficient, or old’. The evidence of effectiveness of influenza vaccination in pregnant women was also limited, identifying only one RCT and one controlled clinical trial: no Data is the information collected through research. were available on effectiveness against seasonal influenza during pregnancy.
The findings of a review on influenza vaccination for healthy adults included 52 Clinical trials are research studies involving people who use healthcare services. They often compare a new or different treatment with the best treatment currently available. This is to test whether the new or different treatment is safe, effective and any better than what is currently used. No matter how promising a new treatment may appear during tests in a laboratory, it must go through clinical trials before its benefits and risks can really be known. of over 80,000 people and provided The certainty (or quality) of evidence is the extent to which we can be confident that what the research tells us about a particular treatment effect is likely to be accurate. Concerns about factors such as bias can reduce the certainty of the evidence. Evidence may be of high certainty; moderate certainty; low certainty or very-low certainty. Cochrane has adopted the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) for assessing certainty (or quality) of evidence. Find out more here: https://training.cochrane.org/grade-approach evidence that influenza vaccines probably reduce influenza in these people from 2.3% without vaccination to 0.9%, during a single influenza season.
A separate but complimentary review looked at the evidence on influenza vaccination in healthy children. This review included 41 clinical trials and over 200,000 children. This showed with moderate-certainty evidence that, when compared with placebo or doing nothing, influenza vaccines probably reduced the A way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of influenza infection in children aged 3 to 16 years from 18% to 4% over a single season. Somewhat surprisingly, the evidence from these studies on the adverse effects of vaccination (such as time off school or work) and the positive consequences (such as a reduction in complications like pneumonia) was lacking both in quality and quantity.
These reviews have undoubtedly been helpful, identifying vaccine effectiveness in adults and children but also recognising important research gaps in vulnerable populations such as older adults and pregnant women. It’s clear that in 2018 we need to move forward by conducting more research in this area, building the evidence and examining it critically, not accepting our fate ‘stoically’.
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Emma Plugge has nothing to disclose.