Multiple Vaccinations on Same Day Does Not Raise Autism Risk

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Infants now receive several shots at a time, but the latest study says that does not increase their risk of developing autism.

About one-third of parents are concerned about unsubstantiated claims that vaccines can cause autism. And although research, including an analysis by the Institute of Medicine, has not found a causal relationship between vaccines and the developmental disorder, one in 10 parents still delay or refuse to vaccinate their children according to the Center for Disease Control’s childhood immunization schedule.

Intuitively, parents believe that the amount of antigens, or immune-activating agents in the shots, over-burden young babies’ still-developing immune systems, making them more vulnerable to developing autism. So many parents “shot-limit,” or stagger the immunizations their infants receive, spreading them out rather than vaccinating their children at the recommended 2, 4, and 6 month visits. There is no evidence, however, that delaying the various doses of the 14 different vaccinations recommended in the U.S. are safer for kids.

And the latest study investigating the practice, published in the Journal of Pediatrics, continues to show there is no association between autism and receiving “too many shots too soon.”

The researchers reviewed data involving 256 kids with autism spectrum disorders (ASD) and 752 without ASDs. By examining their vaccination schedules, the scientists calculated the maximum amount of antigens from the shots each child received during a single doctor’s visit to determine how stimulated the babies’ immune systems were to create antibodies against the diseases for which they were vaccinated. They also calculated the infants’ overall antigen exposure in three different groupings — from birth to three months, from birth to seven months, and from birth to two years, by which time most youngsters should have received the bulk of their childhood immunizations.

(MORE: Vaccine Safety: Why Parents’ Alternative Immunization Schedules May Cause Harm)

For each age grouping, the scientists compared exposure to antibody-producing antigen and risk of ASDs. By age two, most properly vaccinated children should have been exposed to about 315 different antigens from disease-causing agents such as measles, tetanus and pertussis. They could not find any increase in incidence of autism-related diagnoses with increasing exposure to antigens as the children received more immunizations, and concluded that neither the number of vaccines a child gets before age two nor the number of vaccines a child gets in a single day were associated with developing autism.

The researchers acknowledge that children today receive more vaccines than they have before, but that doesn’t mean they are being exposed to more antigens. In the 1990s, for example, infants were exposed to thousands of antigens, rather than the current 315, from their immunizations. That’s because some shots have been redesigned to stimulate antibody production with fewer antigens; the older version of the pertussis, or whooping cough shot that included the whole bacterium, for instance, produces around 3,000 different antibodies while the new vaccine that incorporates only a snippet of the pathogen produces less than six. The scientists also stress that an infant’s immune system can successfully confront a heavy burden of such bacterial or viral stimuli, and that babies are exposed to hundreds of viruses in their environment.

“The concern around vaccines has been a very significant issue. Many parents are now deciding to wait or space out vaccines. There has been a concern that when parents are worried about whether vaccines are associated with autism that they are going to choose not to vaccinate their child,” says Geraldine Dawson, the chief science officer for Autism Speaks. “That’s one of the reasons we see this as very good news, because we hope this will reassure parents that the number of vaccines your child received during the first couple years of life is not associated with a risk in developing autism.” Dawson, who is a professor of psychiatry at University of North Carolina Chapel Hill, was not affiliated with the study.

(MORE: Parents Wary of Childhood Vaccines? Here’s How to Persuade Them)

The researchers also found no link between vaccine load and the development of regressive autism–in which a child develops normally and then suddenly loses speech and social skills. The timing of the this regression with the completion of childhood immunizations have been a strong factor keeping concerns about the burden of vaccinations alive in many parents’ minds. “We have been particularly concerned about that subgroup of kids who do have that regression. These are kids who develop normally during the first few years of life and then they lose their skills, usually around their first or second birthday, which is of course right around the time they receive some of their vaccines. This study looked to see if for even this sub group, whether they are more at risk, and again no connection was found,” says Dawson.

While claims about the correlation between vaccines and autism continue to simmer, the body of evidence doesn’t provide any support for the connection. Dr. Andrew Wakefield, the British researcher responsible for raising the alarm about immunizations, lost his medical license in 2010 when his claims about the measles, mumps and rubella shot increasing the risk of autism could not be substantiated. The scientific paper in which he described his theory was also retracted after editors determined the findings were “fraudulent.”

MORE: How Safe Are Vaccines?

Dawson understands the concerns and confusion that parents have about the safety of vaccines and autism, especially when so much conflicting information is available on the internet to evaluate. “I think one of the biggest struggles for families is that we still do not understand the causes of autism. We know that there are many different causes and I think that until we conduct more research and understand the causes, parents are going to be drawing connections and having many questions and concerns,” she says. While no vaccine is 100% safe, however, the current study’s results should help to reassure parents that the benefits of protecting children from potentially deadly infectious diseases such as measles and pertussis far outweigh potential risks associated with the shots.