The scientists whose research anti-vaxxers use to claim their children should be genetically exempt from vaccines have now said their old work is no longer valid.
Anti-vaxxer doctors and even parents have been ordering genetic tests from companies like 23andMe in search of a variant of the MTHFR gene in their patients and children.
That's because a 2008 study suggested that people with that variant would be prone to 'adverse events' in response to smallpox shots (which are no longer given).
But two of its authors, Dr James Crowe and Dr David Reif now say that our understanding of and methodology for studying DNA have changed so drastically that their decade-old research is no longer valid, they told The Atlantic.
A decade-old study suggested a link between a gene variant and reactions to a smallpox vaccine - which is no longer used - which anti-vaxxers cite to justify medical exemptions. The study's authors say the research is 'no longer valid' by today's standards (file)
California's law against philosophical exemptions to vaccines was passed in 2016 in the aftermath of a brutal measles outbreak that began at Disneyland.
But that didn't stop vaccine wary and anti-vaccine parents - still concerned over now-debunked research linking the MMR vaccine to autism - from finding ways to get their children out of the shots.
In the last two years, the number of 'medical' exemptions from shots issued in California has tripled, according to a JAMA report.
And just because it's labeled 'medical' and issued by a doctor, doesn't necessarily mean they are medically valid.
For example, Dr Kenneth Stoller in San Francisco was subpoenaed earlier this month by the city attorney on suspicion that has been issuing improper vaccine exemptions and profiting from the practice.
According to city attorney Dennis Herrera has been using no more than 'two 30-minute visits and a 23andMe genetic test' to determine that children should be exempt from shots.
Online resources, too, instruct consumers on how to upload the raw data from their at-home DNA tests to look for a variant of a gene called MTHFR (which 23andMe's genetic profiling will detect, but the company doesn't specifically test for), that has been linked to 'adverse effects' from smallpox vaccinations.
But 23andMe itself says that its tests should not be used as the basis of medical decisions.