GEORGE TOWN, July 19 – Despite some belief, numerous and exhaustive studies worldwide have found no link between inoculation and autism, according to the National Autism Society of Malaysia (Nasom).

The society's Penang advisor, Dr Sim Joo Seng, said one reason why there is so much research in this particular area was the unproven claims by anti-vaccination groups in the West, adding that none of the studies conclude that vaccines ― including the oft-maligned triple dose Measles, Mumps and Rubella (MMR) jab ―  cause of autism.

"In fact, science has not been able to find the actual cause of autism although there are a lot of theories," he said.

The paediatrician said the anti-vaccination group had initially blamed mercury-based preservative thimerosal as the cause of autism but all research on this has failed to find any association.

"They have also taken out thimerosal from vaccines for many years since 2001 and yet autism is still on the rise worldwide, so this showed it is not the cause at all," he said.

He added that experts on autism spectrum disorder (ASD) believe that most cases are caused by a combination of factors such as genetic predisposition and environmental factors.

"Until now, nobody can pinpoint the real cause of autism except that it could be due to many factors such as genetics, environment and maybe even infections," he said.

Though anti-vaccination groups have been actively spreading their fears in the West for over 20 years, the movement has only reached Malaysian shores recently.

But it was enough to move Penang state health executive councillor Dr Afif Bahardin, who exposed the growth of this movement, to warn against the consequences of refusing vaccination.

The state health department has identified a group of fewer than 50 people who refuse vaccination for their children in Penang, and are now visiting these families to counsel them.

Beyond autism fears, anti-vaccine groups here were also categorising the shots as a "new world order to undermine the Muslims"; Dr Afif, however, reassured all Muslims that the vaccines are fully halal (permitted in Islam).

Dr Sim said these groups were able to spread their beliefs using the power of anecdotal accounts, often based on case study reports or random investigations, instead of systematic scientific evaluation.

"They get anecdotal evidence of random cases of a child who went for MMR shots at 15 months and, a few weeks later or a few months later, the child developed ASD so they attributed it to the vaccine," he said.

In the West, the MMR jab is administered to children at 15 months; here, the inoculation is done at 12 months of age. This period also coincides with when symptoms of the disorder usually begin to manifest, leading some to conclude correlation as causation.

"The ages of 15 months up to 18 months is usually the time when ASD symptoms are noticed so this coincidence has led to many people blaming MMR as the cause of ASD," Dr Sim said.

He warned that if these anti-vaccine groups are able to spread their fears to the larger population, diseases once thought eradicated would stand a chance of returning and putting the country at risk of being ravaged by epidemic.

"For now, they are a small group so they are still not susceptible due to herd immunity afforded by 95 per cent of those who are vaccinated, but if there are more of them, they will not be protected anymore and the diseases will spread very fast," he said. Citing measles as an example, the doctor noted that airborne nature of its spread would mean a rapid outbreak if large parts of the population are not immune.

"Measles can cause serious health complications such as pneumonia, brain infection and death," he said.

While he concedes that vaccines are not completely free of side effects, Dr Sim said these were limited compared to the debilitating and sometimes-fatal diseases they prevent.

"Maybe one out of a million people who received vaccines may contract encephalitis but if they don't get vaccinated, one out of 1,000 who contracted measles will get encephalitis," he explained.

Among other diseases for which vaccines are available are whooping cough, diphtheria, polio, rubella and Haemophilus influenza, all of which can potentially lead to complications that includes brain damage and death.

Dr Sim added that only a small number of people with medical conditions such as immune deficiency syndrome, mitochondria or metabolic syndrome will have to be careful in the dosage of vaccines they receive.

"As for the rest of the population, there are more benefits to vaccination than bad," he said.