Just in case you needed further convincing, a new study that examined medical records from more than 81,000 American children has found absolutely no increased prevalence of autism spectrum disorder (ASD) in children whose mothers received vaccines for potentially deadly infections while pregnant.
The analysis, published today in the journal Pediatrics, was performed by Kaiser Permanente researchers using data from children born at southern California Kaiser hospitals between January 2011 and December 2014. The vaccine of interest in this case – the infamous link to the measles, mumps, and rubella (MMR) vaccine has already been thoroughly discredited – was the Tdap, a combined immunization that protects both mother and baby against the three pathogenic bacteria species that cause tetanus, diphtheria, and pertussis (also known as whooping cough).
Among the 81,993 naturally conceived children included in the study, 1,341 were clinically diagnosed with ASD between their first birthday and June 2017. The incidence of the disorder in the vaccinated group was 1.5 percent, compared with 1.8 percent for the unvaccinated group. After adjusting for numerous potential confounders, including child’s birth year, whether the baby was born prematurely, ethnicity, maternal age, maternal education, geographic location, start of prenatal care, flu vaccination during pregnancy, and whether the child was the first born (past work has indicated that birth order affects development of ASD), the authors concluded that there is no risk of ASD from Tdap.
"The link between vaccination and development of autism has been refuted by many rigorous scientific investigations. Unfortunately, the misconceptions still generate concerns," senior author Hung Fu Tseng said in a statement.
"Given the increasing practice to vaccinate pregnant women with Tdap vaccine, it was important to address the concern of a link between maternal vaccination and subsequent development of autism spectrum disorder in children," he added. "We hope that our findings reassure parents that Tdap vaccination during pregnancy was not associated with autism in children."
Tseng and his colleagues note that the proportion of expecting women who elected for Tdap vaccines grew during the study period, from 26 percent in 2012 to 79 percent in 2014. The Centers for Disease Control and Prevention, the American College of Obstetricians and Gynecologists, and the American College of Nurse-Midwives all recommend that pregnant women receive a Tdap during their third trimester so that their babies will have antibodies for these bacteria upon birth.
Interestingly, the overall rates of ASD declined during the study period, from 2.0 to 1.5 percent in the unvaccinated group and from 1.8 to 1.2 percent in the vaccinated group. Though no single factor has yet to be definitely linked to ASD, inherited variations in several dozen genes regulating brain activity have been implicated, as have environmental factors that could induce epigenetic changes, such as exposure to high levels of maternal testosterone in utero.
Not knowing how to reduce the likelihood that your child will have this disorder – and thus struggle with social interaction – may be scary for parents, but as literally all the credible peer-reviewed science supports, refusing to vaccinate is not the solution. Immunizations are essential not only for the health of your child but also for the health of human populations as a whole.