The importance of relative risk in understanding vaccine effectiveness

A while back I noticed that Greg Beattie was deceiving his readers about pertussis vaccine efficacy by misrepresenting NNDSS data.

Yes, the same Beattie with the bogus claim that vaccines did not reduce infectious diseases. He dresses this up with misleading graphs comparing mortality from vaccine preventable disease to the introduction of X vaccine. These graphs are also bogus in that he omits the impact of vaccine introduction. The stunning success of the vaccine itself and the elimination of infection is always absent from his peculiar artwork.

Beattie’s claim back in 2012 was that the pertussis vaccine failed because high numbers of notifications had been vaccinated against pertussis. This is thunderously misleading in that it’s at the same level as dismissing seat belt safety because most fatalities on our roads involve seat belt wearing occupants. He also avoided explaining all reasons as to why notifications were high. Increased awareness, testing and follow up, pockets of low vaccination driving an epidemic, low booster uptake.

You can check the post here to follow my review of the same data table Beattie used. But it’s pretty simple. By 2011 close to 95% of 0-4 year olds were fully vaccinated by age 2 [NCIRS]. Using the table provided it turns out those not fully vaccinated made up 27.2% of notified infections. Fully vaccinated notifications equal 56.7%.

Relatively speaking a child fully vaccinated against pertussis has a notably reduced chance of being infected. Conversely, the small number who are not fully vaccinated have a frightfully high chance of being infected. To be sure, if 56.7% of notifications collected over 2008 – 2011 are from fully vaccinated children one can argue the vaccine could (and needs to be) more effective. But when the 5% who are not fully vaccinated make up 27.2% of infections, then the claim the vaccine is not effective is patently absurd. A dangerous and irresponsible lie.

Basically this is a story of relative risk being falsely presented as absolute risk. Choose some data and omit other data and the claim looks sound. But the post itself is limited in examining Vaccine Effectiveness vs Relative Risk (Risk Ratio – see screenshot). Understanding related and relative data sets is crucial in grasping how vaccine efficacy can be misrepresented. Regrettably many falsehoods peddled by the anti-vaccine lobby stem from such misrepresentation.

Fortunately an excellent piece addressing this was recently published on The LymphoSite by kill3rtcell. Headed But most of the people who got the disease were vaccinated for it! the post comprehensively addresses vaccine effectiveness, risk ratios and even provides interactive calculators. These crunch values of vaccine effectiveness, vaccination rates and resultant cases in the unvaccinated or vaccinated.

Do head over and read what is an excellent contribution to the deconstruction of misinformation peddled by antivaccinationists.

The screenshot below helps explain what this post accomplishes.

relative risk

© kill3rtcell – The LymphoSite

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About @advodiaboli
I'm not really a cast iron flying pig.

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