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.


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