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Malaria vaccines: fifty percent of what?

Carl Heneghan
Last edited 21st October 2011

This week there was substantial news coverage about the effects of a new malaria vaccine. This is what Fergus Walsh of the BBC said, “The first phase three results, published online in the New England Journal of Medicine, show that the vaccine cut the risk of malaria infection and several malaria - by about half.” The Guardian’s Sarah Bosely chipped in with “The vaccine had been classed as around 55-60% effective,” and allAfrica.com reported “Malaria Vaccine Will Reduce Infection in Children By Half.”

Did you interpret the result to be meaningful, you and nearly everyone else?

Surely a 50% reduction in malaria is such a big effect that the vaccine is rolling of the production line right now. There is no doubt that a vaccine for preventing malaria would be a major health advance but the question immediately on mind was, 50% of what?

Only by accessing and working your way around the original publication can you get to the real figures. Which, I have to say, it wasn’t easy to get to, and interept the data I wanted. Is debate stifled by the incisive way journals publish papers which seemingly skirt around the data that matters, leaving you ever so slightly confused and dazed?

I think it's one of the reasons most media reports just focus on the press release. The papers themselves are written in a code which is only decipherable to mere humans after numerous re reads of the article. It probably also takes too long for most to read through the studies partcularly in the modern media world of instant news.

So what does the data reveal? The results of the trial are published in the New England Journal of Medicine shows during 12 months of follow-up in the first 6000 children the incidence of the first or only episode of clinical malaria was 0.44 per person-year in the vaccine group and 0.83 per person-year in the control group giving a relative reduction of 56%.

However, when you look at severe malaria 57 of 2830 children (2.0%) in the vaccine group and in 56 of 1466 children (3.8%) in the control group had at least one episode. A relative reduction of 47%.

As you can see the two figures for the same relative effect have very different absolute effects based on the severity of the outcome.

Yet, for death there was no difference: 56 of 5949 children (0.9%) died in the vaccine group and 28 of 2974 children (0.9%) in the control group.

So are you a relative or absolute person. I’m both, but I seem to be getting more sceptical the more headlines I read. You should be too

Just a spoonful of sugar, to help the obesity epidemic go down

Kamal Mahtani
Last edited 19th October 2011

Teaching on an Evidence Based Practice workshop recently I came across a truly jaw-dropping projection. A participant used a clinical scenario about obesity to bring up a paper about the US Obesity epidemic.The study is three years old now, but the authors use data on adults and children from the National Health and Nutrition Examination Study (NHANES), between the 1970s and 2004. The projections are frightening for the burden and health-care costs of obesity and overweight in the US if current trends continue. By 2048, all American adults would become overweight or obese. Depending on your ethnic background it could even be worse with the authors stating that Black women and Mexican-American men are likely to reach that state even earlier. However, the authors point out that they make a number of assumptions. Firstly they assume that the increase in obesity will be at its current rate. They also ignore the effect that all future policy, environmental and behavioural changes may have. Finally they ignore the possibility that some individuals may be genetically protected from becoming obese.

In the UK the predictions are not that much better. A recent four part series on obesity in The Lancet journal included a paper co-authored by Professor Klim McPherson of The University of Oxford. Their study stated that by 2030 there would be an additional 11 million more obese adults in the UK. This would have a knock on effect of an extra 6-8 million cases of diabetes, 5—7 million cases of heart disease and stroke and approximately 600,000 additional cases of cancer. This sort of news travels fast with The Daily Mail being one of the first to report these finding to the public.

So is it all doom and gloom? Not necessarily. In the same paper the authors go on to suggest that a 1% reduction in BMI (equivalent to a 1kg loss) across the entire population could avoid up to 2 million incident cases of diabetes, nearly 2 million new cardiovascular disease cases, and 73 000–127 000 cases of cancer. The authors further infer that this could be achieved through a reduction of 20kcal/day sustained over 3 years i.e. less about a teaspoon of sugar a day. Better still, if we were all able to give up 200 to 400 kcal/day, obesity levels would drop to 1990 prevalence levels.

So small changes may be the best way to start beating this epidemic. Something to think about before adding that spoon of sugar to your next tea or coffee.

Age ain't nothing but a number

Ami Banerjee
Last edited 14th September 2012

Yesterday’s news hero was 100-year old Fauja Singh who finished the Toronto Waterfront Marathon to enter the Guiness Book of Records as the oldest man to ever complete a marathon. After reading so much about obesity, lifestyle risk factors and the chronic disease epidemic, it is great to hear that this Sikh gentleman has reached his age and maintained his fitness by sticking to ginger curry and tea.

Age and the “elixir of life” seem to be the theme of the news this week. Scientists fully decoded the genome of the world’s oldest woman who died in 2004 at the age of 115 years. This lady had no signs of dementia whatsoever and her good health has led to hopes that her genome will provide clues to her longevity. A herring-rich diet may have had something to do with it.

Ageing research is big money and a big priority. At the National Institutes of Health (NIH), over US$2.5 billion will be spent on ageing research this year, and the UK has been strengthening its ageing research portfolio and networks for the past few years. Scientific journals have blossomed around the search for life-prolonging knowledge. Did you know there was a journal called “Rejuvenation Research” ?

In clinical trials and research studies, if a difference is detected between two groups of individuals, often the first step in analysis is to “adjust for age”. In plain English, that means if we get rid of the differences between two groups which are just caused by differences in the ages of the individuals in the two groups, then we can assess if there are any other differences. It has always seemed counterintuitive to me that we do not also routinely adjust for sex, ethnicity, education, socioeconomic status and any number of other risk factors which can cause differences between groups of people.

With the make-up of our societies shifting more in the direction of elderly populations with increasing chronic diseases, the focus of research is shifting to how age itself contributes to disease processes and how we might reverse age-related processes. But are we focusing too much on just one factor? Age is undoubtedly a major contributor to many diseases and their underlying development but we cannot look at age in isolation. Fauja Singh and other healthy ageing adults reach their old age due to the complex interactions between genes, environment and chance, like every disease that medical science has so far uncovered. So to just look at his genes for the answer or for everybody to start on a diet of ginger curry does not make sense to me.

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