One of the linchpins of the anti-vaccine movement is the attempt to muddy the issue with regard to vaccine efficacy. From this point various others follow; if vaccines are ineffective then large risks need not be shown – any risk at all makes being vaccinated an unwise choice. If vaccines do not perform their role then “forcing” people to vaccinate their children is unwarranted.
Lucky for them many of the diseases vaccinated against had the debut of their vaccine quite some time ago which makes it easier to cloud the issue as to causation: perhaps the disease was waning naturally, perhaps it was improved sanitation etc.
Lucky for us vaccine development continues and new vaccines get evaluated down the line to determine effectiveness. This gives us a more recent look how vaccines work and their impact on the population that is not as susceptible to these tactics.
For example, pneumonia is a risk for young children and hospitalisations in the US prior to 2000 hovered around the 1,200 per 100,000 mark. In 2000 a pneumonia vaccine was introduced into the vaccine schedule which targeted 7 of the 90 odd bacterial strains that cause the disease. Recently a study was published looking at the effect of the vaccine on incidence of hospitalisations. In particular the researchers were looking to see if the initial drop in hospitalisations seen in 2000 was holding steady considering the other strains that could fill the gap. They also looked at incidence of pneumonia hospitalisation in age groups other than infants (classed as <2 yrs old) to see if the vaccine was having any effects outside of the nominal target population.
I’m not sure if this expanded scope is normal for this sort of study but I gather that the older population tends to contract the disease from the young family members so this sort of cross population effect at least has a plausible mechanism in this case.
So what was found and why did I bring anti-vaccinationists into this?
Well, first off as was hinted above there was a significant drop in infant hospitalisations in 2000 (the year the vaccine was widely introduced) which continued to the end of the study period in 2009, as shown in this graph:
In other words, the vaccine is doing it’s job. It’s hard to argue that there was a significant change in sanitation or general practice between 1999 and 2000 to account for the dramatic and sustained drop as seen. I would like to have seen the incidence prior to 1997 extended further in order to see what the trend for the previous 10 years was. However given that the purpose of the paper was routine surveillance, not to refute anti-vaccine proponents, that’s probably a bit much for me to ask. This 2004 study suggests that childhood incidence of pneumonia is around 3,500 cases per 100,000 (~35 per 1,000 as noted in the paper, adjusted here to give the same units as the current study) but does not specify how many of these would have required hospitalisation.
Secondly the study also found a significant drop in hospitalisations for older people as shown in this graph:
So you don’t even need to receive the vaccine directly to get a benefit from it. That’s already well known but it’s nice to have an instance graphed out like this.
As I started this article, if you can throw doubt on the effectiveness of vaccines then arguing follow up points becomes much easier. A corollary to this is that if people are unaware of the facts around vaccine efficacy they will be unable to counter the miss-information and will either be persuaded by it or fail to effectively argue with those who have been already persuaded.
Previous Articles on the topic of vaccines: