A study of more than 95,000 children in the US has supported what almost two decades of scientific research has already been telling us - the measles-mumps-rubella vaccine (MMR) is safe and effective and is in no way associated with a heightened risk of developing autism spectrum disorders ( ASD).

The study, led by paediatrician Anjali Jain from US health policy analysts, the Lewin Group, focussed on children in a high-risk category for developing autism - those with a family history of the disorder, borne out in their autistic older siblings. "This is the first study to assess risk among children already at higher risk by virtue of having an older sibling with ASD," the team reports in the Journal of the American Medical Association. "Even in these cases, the data showed no increased risk of ASD related to the MMR vaccine."

For most of us, there isn't even an argument - the evidence is so one-sided there's nothing to debate. Even the paper that started the whole debacle in 1998 has been well and truly retracted. But there's a vocal minority that remains convinced that vaccines are dangerous to children.

Earlier this month, we reported that the Australian government will no longer be paying childcare and welfare benefits to parents who refuse to vaccinate their children as of 2016, in an effort to put a serious dent in the movement that has seen 39,000 Australian children miss out on vaccinations due to the soon-to-be-abolished 'conscientious objection' exemption from mandatory vaccinations. And that's just Australia. In the States, while the national average rate for unvaccinated people is still low, it's actually growing.

According to Sarah Mimms at the National Journal, during the first five months of 2014, doctors reported 288 cases of the measles - a disease that was technically eradicated from the US in 2000 - representing 15 separate outbreaks across the country, and a 20-year high for the disease. "Meanwhile, pertussis, or whooping cough, cases are up 24 percent over last year," says Mimms.

And things are even more dire when it comes to children already living with ASD. In a recent survey cited by Jain and her colleagues, of 486 parents of children with ASD in the US, it was found that nearly 20 percent of them had decided not to vaccinate their younger children. "A Canadian study of 98 younger siblings of children with ASD found that younger siblings were less likely to be fully MMR immunised when compared with their older siblings with ASD," they report.

So some people still need convincing. This new study is pretty damn convincing. Jain and her colleagues collected data from an extensive private health insurance database of 95,727 children born in the US between 1 January 2001, and 31 December 2007, each of whom had at least one sibling who was between 6 months and 17 years older. They then compared the instances of ASD, looking at familial trends across the siblings, and the rate of exposure to the MMR vaccination.

The team discusses the link between siblings with ASD and the lowered rate of vaccination in children of ASD-affected families in the paper:

"Out of 95,727 children in the cohort, 1,929 (2.01 percent) had an older sibling with ASD. Overall, 994 (1.04 percent) children in the cohort had ASD diagnosed during follow-up. Among those who had an older sibling with ASD, 134 (6.9 percent) were diagnosed with ASD, compared with 860 (0.9 percent) diagnosed with ASD among those with siblings without ASD. 

The MMR vaccination rate for the children with unaffected siblings (siblings without ASD) was 84 percent at two years and 92 percent at age five years. In contrast, the MMR vaccination rates for children with older siblings with ASD were lower (73 percent at age two years and 86 percent at age five years)."

As parents are currently advised to vaccinate their children twice for measles, mumps, and rubella between birth and the age of five, the team looked for links between the MMR vaccination and ASD across two sets of vaccinations. They found nothing:

"Consistent with studies in other populations, we observed no association between MMR vaccination and increased ASD risk among privately insured children. We also found no evidence that receipt of either one or two doses of MMR vaccination was associated with an increased risk of ASD among children who had older siblings with ASD. 

As the prevalence of diagnosed ASD increases, so does the number of children who have siblings diagnosed with ASD, a group of children who are particularly important as they were under-vaccinated in our observations as well as in previous reports."

Add this to the 2004 Institute of Medicine study that analysed a huge set of epidemiological evidence and found no link between the two, and their 2011 examination of eight commonly used vaccines that found the same thing. "And we stopped even counting pro-thimerosal papers, after nine studies from several countries proved that the mercury-containing chemical was entirely safe," says Joshua A. Krisch at Vocativ. The evidence is there - it's just not the evidence anti-vaccers are looking for. But it's time to face the facts, and let researchers spend their time investigating something else.

"Some dozen studies have shown that the age of onset of ­autism spectrum disorders does not differ between vaccinated and unvaccinated children, the severity does not differ, and now the risk of recurrence in families does not differ," University of Washington psychiatrist Bryan King, who was not involved in the research, told John Ross from The Australian. "Short of arguing that the MMR vaccine actually reduces the risk, the only conclusion is that there is no signal to suggest a relationship (with) autism."

Sources: Vocativ, The Australian,  National Journal