Although children and young adults are more likely to get measles, mumps, rubella (MMR) and varicella (also known as chickenpox), which can lead to fatal illnesses, disabilities and even death, some parents have stopped having their offspring vaccinated for fear that these injections cause autism. Now, new findings confirm the effectiveness of these vaccines, further debunking the myth that immunizations cause autism and other health problems, Cochrane reports.
The MMR vaccine protects against all three infections, while varicella can be prevented with a combined MMR and varicella vaccine (MMRV) or via two individual vaccines administered at the same time (MMR+V).
For the review, researchers assessed the usefulness, safety and long- and short-term harms of the vaccines by looking at 138 studies that included 23 million children. Studies showed that one dose of vaccine was 95% and 72% effective in preventing measles and mumps, respectively.
Measles cases could decline from 7% in unvaccinated children to 0.5% in those who receive just one dose of the vaccine, while two doses showed 96% effectiveness. For mumps prevention, two doses could result in 86% effectiveness with cases falling from 7.4% in unvaccinated kids to 1% in those who take this dose.
In addition, vaccines were found to be potent against rubella and chickenpox. One inquiry showed that one dose of vaccine was 89% effective in preventing rubella, while another study found that the MMRV vaccine was 95% effective against chickenpox infection after 10 years, meaning only 5 out of 100 vaccinated children would contract chickenpox if exposed.
Most important, two studies involving more than 1 million children determined that the numbers of diagnosed cases of autism were similar in both those who were vaccinated and unvaccinated.
Moreover, two studies also revealed no association between MMR vaccines and encephalitis (brain inflammation), inflammatory bowel disease, Crohn’s disease, cognitive delay, type 1 diabetes, asthma, dermatitis or eczema, hay fever, leukemia, multiple sclerosis, gait disturbance (a deviation from normal walking) or bacterial or viral infections.
“Overall, we think that existing evidence on the safety and effectiveness of MMR/MMRV/MMR+V vaccines supports their use for mass immunization,” said Carlo Di Pietrantonj, of Italy’s Regional Epidemiology Unit SeREMI and the study’s lead author. “Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage.”
Di Pietrantonj noted that more research is needed to determine whether the protective effects of the vaccines might diminish over time.