Health officials say vaccination rates against measles are worryingly low among Somali children in the US and UK because some parents still believe the MMR jab is linked to autism.
The officials say they are struggling to show that the vaccination is safe.
BBC Radio 4's The Report has found that the discredited former doctor Andrew Wakefield visited some Somali groups in the US.
Health authorities there blame him for the drop-off in MMR vaccinations.
Andrew Wakefield, who now lives in Texas, says Somalis in Minnesota already had fears about autism and MMR before his visit.
Somali Bakita Mohamed Haji lives in north-west London with her 10-year-old daughter, who suffers from autism.
She says her daughter's condition started after she was given the jab.
"My daughter was born normally but when I started the MMR, my daughter changed. Screaming all the time, crying. I went to the hospital and they said it's autism. I don't understand it. I'd never heard of it."
She wishes her daughter had never had the injection, which she believes caused the condition.
Health experts say her fears, and those of other parents, have been reinforced by a common belief in their community that only the children of Somali families that emigrate to the West develop autism, whereas those who stay at home do not.
While there is no solid evidence to confirm this, a small study of immigrants in Stockholm, the Swedish capital, did suggest that families using services for autistic children were more likely than expected to be from West and East Africa.
And separate research in the UK also found there was a higher than average incidence of autism in children born to African mothers - but it did not establish a reason why.
The fears of Somali parents echo those sparked by a study in The Lancet medical journal that linked MMR with autism.
The study was discredited and withdrawn. Andrew Wakefield, the lead author, was struck off by the General Medical Council because of ethical concerns about his methods.
A subsequent raft of research has found no link between the MMR vaccine and autism, and average vaccination rates are back up to 94% in England for five-year-olds receiving the first dose of MMR.
But take-up of the vaccine is much lower among Somali children in the UK and in the US.
In Minnesota in the Midwest, the Somali American Autism Foundation has pledged to find out what causes the condition in their children.
Idil Abdul runs the foundation and has a son, 10, who is autistic.
"If your child is sick, the goal is you take them to the doctor and the doctor tells you what's wrong with the kid and how to make him better. With autism, we go to the doctor and they say, 'We don't have a cause, we don't have a cure, too bad, so sad, you might not get access to early intervention, have a nice day.'"
She does not believe there is a link between MMR and autism but says parents are frustrated because they do not feel their concerns are being listened to by the authorities.
'Planted the seed'
Andrew Wakefield visited Minnesota at least three times between 2010 and 2011, promising research to find answers to their questions.
The Minnesota department of health says his visit contributed to a drop-off in MMR uptake among Somalis and says only around 50% of Somali children now receive the vaccine.
Kristen Ehresmann, the state's director of infectious disease, believes he had an influence on Somali perspectives.
"There were a number of individuals who reached out to the community who planted the seed that there might be concerns about vaccination and what role it could play.
"Since that time we've seen vaccination rates drop off accordingly."
Andrew Wakefield denies his visit caused the drop in Somali children having the MMR jab, claiming the trend was already happening.
He said: "The reason that I was invited was to help address the Somalis' pre-existing fears about developmental regression in their children following MMR immunisation."
Although there are no official statistics, vaccination rates are also believed to be low among Somali children in London.
Shukri Osman, a parent of an autistic child, estimates that only half the Somali parents she knows have taken up the vaccine.
She lives in Brent in north-west London. The local council said: "There are a number of groups and communities in Brent where uptake rates for immunisation have been low. Low uptake rates in the Somali community has been recognised for a number of years."
It is currently training up "community vaccination champions" and now has an immunisation team with Somali-speakers.
Prof David Salisbury, the director of immunisation at the Department of Health, said: "We know that there is not an association between MMR and autism, and that I'm sure has been said many times to Somali community leaders."
But even he admits it will be hard to change what may have become engrained perceptions.
"I think we know it is very difficult to dislodge beliefs from whatever community if they're dealing with a disease that isn't adequately explained on the basis of the cause. "