Herd of immunity?

DONNELLE BELANGER-TAYLOR
Last updated 13:08 22/01/2013

I'm a parenting geek. I do my research. I think it's vital to gather information, paying close attention to the credibility and methods of the sources.

Therefore, my children are immunised. 

They're not in the minority, but sometimes it feels like it. People who choose to have their children receive immunisations just aren't as vocal as those who opt out or follow one of the delayed schedules. 

Some of these vocal anti-vaccine people are up in arms about their representation in this story, an unimmunised boy who contracted tetanus. The seven-year-old spent 26 days in hospital, and faces a year of rehabilitation, learning to eat and walk again. (I wish him and his family all the best for his recovery.)

One blog claims that there is only publicity about this case of tetanus because he was unimmunised. A case in September 2012 didn't receive publicity, and their theory is that the media didn't mention it because that person was immunised.

There is no evidence supplied for that, by the way, and I can think of several reasons why it may not have appeared in the media. Let's be frank: what's more likely, "a conspiracy theory to cover up an immunisation failure" or "the family didn't go to the media"?

There's no denying people can have strong opinions about immunisation. Yes, some people have bad reactions. Yes, sometimes the immunisations fail and people get sick anyway (from experience, I would not wish measles on anyone). On a personal level, it is awful and distressing.

But on a population basis, there is no denying the power of immunisation. (I should be more specific. Some people do deny it. Often they then describe how they use homeopathy to stay healthy.) 

Here I will quote from the Ministry of Health's Immunisation Handbook 2011, Chapter 5:

Almost all the recent cases of tetanus in New Zealand, in both adults and children, occurred in individuals without a documented history of a primary immunisation course of a tetanus-containing vaccine. 

A quick analysis of the data given for the 7 cases in 2009 (most years have only one or two cases) shows three were unvaccinated, one hadn't had a booster since 1995, and three were of unknown status (but likely to be unvaccinated, since "[a]nyone born before 1960 is less likely to have received a primary series, unless they were in the armed forces. Older women appear to be at particular risk.").

Tetanus is an interesting example, though; it's caused by a toxin produced by a bacteria which has been introduced to the body through a wound, so it's not contagious. If you choose not to be vaccinated against tetanus, it's only you at risk.  Or your child, since you're making that decision for them.

Not all vaccine-preventable diseases are so self-contained, though.  Whooping cough, measles, rubella, diptheria, polio - these can have severe consequences to people in your community. Herd immunity matters.

I fully support the right of any parent to make informed decisions... but look at the science.

And think of your neighbour.

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