April 07, 2020
Stacy San Diego, MD
Measles, an easily transmissible yet preventable disease, is experiencing resurgence. A new strain of the disease has not developed but a new strain of ignorance among people has emerged. Incorrect and misleading information can be easily obtained nowadays, thus the rise of misinformed individuals who are against vaccination.
The anti-vaccination movement became popular when a 1998 paper from The Lancet concluded that “possible environmental triggers” (i.e. vaccine) were associated with the onset of both gastrointestinal disease and developmental regression. The author reported that parents of 8 of the 12 children vaccinated associated their child’s loss of acquired skills, including language, with the MMR vaccination.
After 12 years, the article was retracted by The Lancet and the author was discredited because of misconduct and dishonesty. Despite the article being ill-intentioned and not evidenced-based, many people still believed it. Measles is a potentially deadly and debilitating disease but when celebrities and influencers spoke out against some vaccines, it became difficult to regain the trust of parents.
Incorrectly Blaming Vaccines
When did vaccines come under scrutiny? Some individuals were concerned of a vaccine’s thimerosal or ethyl mercury content. Knowing that alone can make any parent scared. If the mercury type thermometers were discontinued and yet the mercury in it does not even make direct contact with our skin, what makes the injection of a similar compound safer? Why was it incorporated in the first place?
Thimerosal is added to vials of vaccine that contain more than one dose (multi-dose vials) as a germicide. However, the MMR vaccine never contained such amount. Numerous studies have proven this type of compound is safe under controlled amounts as supported by the Food and Drug Administration, the Centers for Disease Control, and the American Public Health Association.
The reason behind the specific criticism of MMR vaccine is its vaccination schedule. It is administered to 12 to 18-month-old children. At this age, the first signs of an impending developmental disorder become more noticeable. The idea that 'vaccine precedes event, hence vaccine causes disease’ fits the cognitive bias and misled a lot of people.
Evidence of Safety
The most recent study that tackles the association of Autism and MMR is from a Danish research published in the Annals of Internal Medicine. This is a large single study comprising of 6,517 cases of ASD (incidence rate, 129.7 per 100,000 person-years) from a population of 657,461 children.
It addressed several issues not explored before by previous studies such as incidence of repressive autism and children at high risk for autism. To be able to define high risk children, the autism risk score was computed based on the autism risk factors and components. These were low birth weight, maternal age, paternal age, and smoking during pregnancy, method of delivery, preterm birth, 5-minute Apgar score, low birthweight, and head circumference.
History of siblings with an autism diagnosis was a separate variable. Autism was defined as a diagnosis of any of the autism spectrum disorders or ASD (autistic disorder, atypical autism, and other pervasive developmental disorder or unspecified pervasive developmental disorder).
After a 10- year follow up, the study concluded and found no support for the hypothesis of increased risk for autism after MMR vaccination; no support for the hypothesis of MMR vaccination triggering autism in susceptible subgroups characterized by environmental and familial risk factors; and no support for a clustering of autism cases in specific time periods after MMR vaccination.
In further analyses, the investigators also looked for links between vaccinations other than MMR and autism; again, they found none. One of the study's main strengths is the large number of individuals included in the analysis. The study's size allowed the authors to conclude that even minute increases in autism risk after MMR vaccination are unlikely.”
Jain and colleagues (JAMA, 2015) used a retrospective cohort study with children continuously enrolled in the health plan from birth to at least 5 years of age during 2001-2012 who also had an older sibling continuously enrolled for at least 6 months between 1997 and 2012 as participants.
The study intended to report ASD occurrence by MMR vaccine status in a large sample of US children who have older siblings with and without ASD. It concluded that receipt of the MMR vaccine was not associated with increased risk of ASD, regardless of whether older siblings had ASD. These findings indicated no harmful association between MMR vaccine receipt and ASD even among children already at higher risk for ASD.
An evidence-based meta-analysis of case-control and cohort studies in 2014 authored by Taylor and colleagues revealed no relationship between vaccination and autism or ASD nor was there a relationship between autism and MMR or thimerosal or mercury. Similarly, the case-control data found no evidence for increased risk of developing autism or ASD following MMR, mercury, or thimerosal exposure when grouped by condition.
The Extent of the Problem and its Solution
There is continuing growth of evidence that vaccines are safe. Although vaccines are without risks, autism is not one of them. For the past 2 decades several studies have been published supporting this data. But these do not seem to help because for nearly a decade, vaccination coverage for measles did not get past the 85 percent mark.
The World Health Organization (WHO) recommends about 95 percent coverage to stop outbreaks from happening. Global coverage with the first dose of measles vaccine has stalled at 85 percent. Second dose coverage stands at 67 percent. The growing hesitancy on vaccines not only with MMR was somehow aggravated by fears from the Dengvaxia controversy.
Smallpox, a highly contagious and deadly disease was eradicated in the 1980s due to the global immunization program. While polio, another communicable but preventable disease still exists, the rates have decreased by over 98% since 1988 from an estimated 350,000 cases to 22 reported cases in 2017. Today, only 3 countries in the world have never stopped transmission of polio (Pakistan, Afghanistan, and Nigeria). (WHO, 2018)
At this stage, information and health teaching is our best ally. It is necessary to educate the public regarding safety and benefits of all other available vaccines through mass education programs and awareness campaigns to overcome fear and confusion. Vaccines work and effectively protect the population through herd immunity.
Considering the scale and scope of this issue, all government and non-government health care authorities must work together in efforts to regain parents’ trust. It will be shameful and unacceptable to be witnessing massive rejection of an absolute solution.
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2. J. Baker. “Mercury, Vaccines, and Autism One Controversy, Three Histories”
American Journal of Public Health (2008 February) 98(2): 244–253.
3. M. Davidson “Vaccination as a cause of autism - myths and controversies”
Dialogues in Clinical Neuroscience 017 Dec; 19(4): 403–407
4. “Thiomersal in Vaccines”
5. Hviid,J. VinsløvHansen,M. Frisch, M. Melbye “Measles, Mumps, Rubella Vaccination and Autism: A Nationwide Cohort Study” 5 March 2019
Annals of Internal Medicine
6. A. Jain, J. Marshall, A. Buikema, T. Bancroft, J. Kelly, C, Newschaffer “Autism Occurrence by MMR Vaccine Status Among US Children With Older Siblings With and Without Autism”
21 April 2015;313(15):1534-1540
7. L. Taylor, A. Swerfeger, G. Eslick “Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies” Volume 34, Issue 28, 14 June 2016, Pages 3223-3224
8. “Measles cases spike globally due to gaps in vaccination coverage” November 2018 WHO https://www.who.int/news-room/detail/29-11-2018-measles-cases-spike-globally-due-to-gaps-in-vaccination-coverage