People who voice their concerns about vaccine safety and efficacy are often dismissed, supposedly because their concerns are not grounded in science. I want to ascertain if this is indeed the case. I started by looking at if there are any researches to determine a causal link between vaccines and autism.
When autism was first described in 1943, its incidence is 4 to 5 per 10,000 children. Now, it is 1 per 10 in US and 1 per 64 in UK. A 10-fold increase in incidence in US was reported in 2001, with 1/120 in 1990 compared to 1/2500 in 1970s (Ratajczak, 2011).
Thimerosal is a preservative that has been used in the manufacturing of vaccines since the 1930s. It contains 49.6% mercury by weight and breaks down in the body into ethyl-mercury and thiosalicylate. From 1930s to early 2000s, many childhood vaccines administered in US contained thimerosal.
Between 1999 and 2001, many vaccines recommended for children under 6 years old were made available in thimerosal-free or thimerosal-reduced formulations. However, exposures to thimerosal through pediatric vaccines still occur in the US and worldwide. Thimerosal remains an important vaccine preservative in resource-poor countries because it allows the use of multi-use vials, which reduces vaccine cost.