Monthly Archives: December 2011

Do vaccines work?

Big news is made about whether vaccination works. See here and here.  (The links are posted not out of endorsement, but to point out to the reader what they may run into). Often times the uproar has a hint of the sinister, fuelled by ulterior motives; however there is  also a lot of misinformation floating around and a significant amount of genuine concern that is fuelled by such misinformation.

Death rates for many infectious diseases have fallen  through out the world. Vaccines have had a great part to play in reducing such deaths. Conspiracy theorists posit that that vaccinations were there at the right place at the right time; that they happened to superimpose themselves upon situations where death rates were already falling, that they are part of a grand conspiracy of the medical-industrial complex unto mankind.

To examine if there is a logical basis for such a point of view, let us take a historical look at the data that is available. We will look at two disease patterns: polio, and measles and how they have been affected by the introduction of vaccines.

Lets start off with disease and death trends for measles.

US Measles death rates

Approximately between 1915 and 1955, case fatality rates for measles dropped by around 100 times in the US and the UK. Measles vaccines were introduced in 1963 in the US and 1968 in the UK.

Opponents of vaccines often latch onto these numbers to discredit vaccination against measles: that measles was already on the wane when vaccines were introduced; and that the vaccine simply laid claim to gains of some other strategy that had worked to reduce death rates.

But here is the rub: measles vaccines have never really claimed to reduce case fatality rates (c.f. total deaths); however what the vaccine has indeed shown to do is that it reduces the number of cases in the first place. Lets take a look at this graph.

US Measles Incidence

Between 1958 to 1962, the United States had an average of 503,282 cases and 432 deaths from measles. Further more, in large city areas, before the introduction of the vaccine, epidemic outbreaks occurred every 2-5 years.

In the US the last epidemic was in 1989-1991. In the last 60 years there has been a 4000 fold decrease in measles deaths. Since 1997 fewer than 150 cases have been reported per year.

In 2000 measles was declared eliminated (meaning there is no endemic transmission) in the US. The majority of the cases in the US since then have either been importations from other areas, or have been in children that have not been immunised.

Which brings us to the earlier part in the discussion, that we stepped aside from: why was there such a drop of 100 fold in measles deaths from the around 1910-1960?

There do not seem to be clear answers here. The trend falls in line with overall falling death rates, but the drop was far more acute to be explained by that alone. Improved nutrition, sanitation, antibiotics (remember it’s usually the secondary infections that kill in measles), the use of high flow oxygen in pneumonia, the introduction of Vitamin A may have had individual roles to play, but none of these factors explain the drop in the entirety.

The less than 3  deaths that we have had from measles in the US for the past 11 years is probably due to a host of factors in association with vaccination; but it it no hyperbole to conclude that high prevalence of vaccination had the single most important role in eliminating measles as a public health threat in the US and much of the Americas.

What’s TB’s problem anyway

You’ve got to give it to the global health community to come up with atrocious goals and targets every once in a while. You might as well have been tempted to discount it for unwarranted grandiosity propelled by their own sense of hubris, had it not been for their penchant for achieving them.

The Stop TB partnership’s attempt to half  TB prevalence by 2015 (base levels at 1990) and  eliminate TB from the face of planet by the year 2050 is one such goal.

To those of us who have been down in the trenches with TB, such an attempt is nothing short of heresy. The problems with controlling TB are manifold. The tools of the trade are ancient. Sputum microscopy, the only available diagnostic tool in much of the world, has limited efficacy and is more than a hundred years old. Isoniazid, the mainstay of treatment everywhere is 60 years old. (See a brief timeline of TB here.) In much of the world the only “recent” innovation in the fight against TB was the implementation of DOTS- which to be sure, has been credited with a lot of success in halting or reversing the tide of  TB in some parts of the world. 

However, the partnership is well aware of the resource and knowledge  gap for the task at hand. Here (table, right) is an estimate of funding requirements up until 2015.

In order to accelerate and prioritize research, the partnership in conjunction with the with the Stop TB Department at the WHO, has come up with the TB Research Movement. Working groups operating across the continuum of  fundamental research to drug and diagnostics to implementation have come up with priority areas for research and knowledge creation to plug existing gaps. Estimates show around 9.8 billion dollars in research are required within 2015, the greatest requirements are for the development of novel therapeutics;  on a relative scale however, research in diagnostics has the largest funding shortfall (graph, below).

Implementation of such an initiative is expected cost around 37 billion dollars until 2015.

The agenda that has been laid out for research has been impressive. TB, despite the close to 2 million deaths that it causes annually, had up until recently been in the back burners of  innovation. The doubt however is if the funding shortfall can be overcome.

Health systems worldwide are already reeling under bitter  economic realities. The US and EU, which have traditionally marshaled resources, are finding it difficult to honor their prior commitments, let alone commit to new ones. The global fund, which has been the go-to funding mechanism for the three major killer communicable diseases, has already withheld its Round 11 of funds in view of the current economic climate, and replaced that with a transitional funding mechanism until 2014.

Hopes have been laid on some other sources of funding, most notably the BRIC (Brazil, Russia, India, China) nations where economic growth has been rapid. These countries incidentally, are also home to some of the largest epidemics of TB in the world.

This isn’t the first time the global health community has set its aims high depite seemingly insurmountable odds. Ten years ago. when the first drafts of the plans to fight the  HIV epidemic where being laid, it appeared as if HIV would wallop entire mankind. With incessant effort and ingenuity, we have been able to turn that tide for the first time. With similar efforts, and a modicum of luck,  we should be able to go even futher with TB, given a lot of  the operational framework for TB program implementation is present in most places, at least  in some form or the other.

The obesity epidemic

Of late there has been a flurry of publication about obesity, both in the scientific as well as the popular press. Either way you look at it, with 34% obesity rates and overweight rates at around 68% in the United States, the numbers aren’t pretty.

What this epidemic of over-nutrition is leading us into though, is outright ugly.

First the problem was seen to be one of the rich world.  In developing countries, obesity had always been thought to  be a disease of the urban affluent; in developed countries the opposite was held to be true. However, as recent research shows, both points of view are crumbling over their own weight.

In low and middle income countries, it still is a disease of the wealthy, especially wealthy middle aged women, but it is now percolating down to the poor people are well.

In rich countries the problem was thought to be largely concentrated among the urban poor, where lack of proper food choices and inappropriate personal choices were said to drive the epidemic; however when 68% of the people are considered to be overweight, the problem is not only in the urban ghettos, but is also right in the middle of the affluent suburbia. In the developed countries no one in really immune any more, and there aren’t just a few easy explanations of poor choices and poverty to explain the epidemic.

The drivers of this epidemic are far more complicated than was previously believed. A four part series on obesity in the Lancet, offers an incisive analysis of the causes and consequences of the obesity epidemic.

Which brings us to the second part of the problem: the consequences. As such obesity has already overrun tobacco as the greatest modifiable threat to public health in many parts of the world. A case in point: tobacco is an addiction in close to a billion people in the world and will contribute to their death in some way or the other in at least one half of them.

As the global burden of morbidity and mortality, shifts from communicable to non-communicable causes, obesity alone can cause already unsustainable health care costs to sky rocket. If current trends continue, in the US and the UK alone, 65 million additional people could be obese by the year 2030, leading to more than 5 million additional cases of diabetes. A roughly  equal number  of additional heart diseases and half a million cancers are also predicted. Year on year additional health expenses in the US alone are expected to be around 50 billion dollars.

A sad truth is despite universal head scratching, we have not really been able to implement strategies to fight off obesity at a population scale. Strategies have been suggested, however conflicting interest groups make it close to impossible to implement strategies that could lead to the reversal of such an epidemic. Furthermore, to complicate matters, we don’t have a single mass scale field-tested  epidemiological intervention that we can pull from and emulate elsewhere that we can use to fight off obesity.

Our gains in health care over the next several decade will largely depend upon how well we are able to mount population level interventions against risk factors such as  obesity. Ingenious research, adept interventions,  forceful advocacy and implementation of population scale strategies will be required to make any dent in the epidemic of obesity.