Thursday, August 21, 2014

A review of 166 independent studies confirms vaccines are safe and effective

They might hurt, but vaccines are safe. Robyn Beck/AFP/Getty Image

It's already well-established that the vaccines commonly used to immunize kids in the United States are safe, and effective at preventing many potentially lethal diseases.

But because of persistent misinformation about the risks of vaccines — and the actual danger caused by parents who choose to not vaccinate their kids — a group of researchers decided to conduct a systematic review of all the controlled studies on vaccines in the scientific literature.

Their conclusion, once and for all: vaccines are safe and effective.

What the researchers found

The researchers, from the RAND Corporation, searched databases of scientific literature for vaccine-related studies, turning up 20 ,478 in total. This included studies of childhood vaccines — such as DTaP (diphtheria, tetanus and acellular pertussis), hepatitis A, hepatitis B, influenza, meningococcal, MMR (measles, mumps and rubella), and varicella — as well as adult vaccines such as flu shots.

Then they boiled this number down to 166 controlled studies — the gold standard of scientific research — in order to directly compare the effects of being vaccinated with the effects of getting a placebo injection or no vaccination.

They found that the vaccines commonly administered to both kids and adults in the US are all safe and effective. Crucially, there was absolutely no link between childhood vaccines and autism spectrum disorders. In other words, kids who didn't get the MMR vaccine (most frequently claimed to cause autism) were diagnosed with autism at the exact same rates as children who did get the vaccine.

Some of the vaccines were linked with mild side effects: the flu shot, for instance, was found to increase the chance of a short-term fever and pain at the injection site.

A few particular vaccines were linked with somewhat more serious, but extremely rare adverse effects. The measles, mumps, and rubella vaccine was found to occasionally trigger allergic reactions (in children allergic to ingredients present in the vaccine) and febrile seizures (relatively common convulsions brought on by high fevers).

But allergic reactions can generally be identified beforehand and properly managed during the vaccination process, and the slightly increased chance of largely harmless seizures is easily outweighed by the potentially huge cost of not getting vaccinated against lethal diseases.

The research is clear: vaccines are safe and necessary for all children.

But we knew all this already

This certainly isn't the first time researchers have rigorously looked at the scientific literature and determined vaccines are safe and effective.

So why are they still doing it? Largely because of the recent swell of prominent anti-vaccine activists, who have used pseudoscience and misinformation to warn against the "dangers" of vaccines. This has led to outbreaks of whooping coughmumps, and measles, putting kids' lives at risk for absolutely no reason.

But, once again, the research is definitive: vaccines don't cause autism, and the potentially costs of vaccines' mild side-effects are clearly smaller than those of the lethal diseases that can spread if we don't vaccinate all children.

This two-minute video, narrated by Vox's Dylan Matthews, provides a great explanation of the anti-vaccination crisis:

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