Final answer:
To address concerns about mercury in vaccines, it is critical to inform parents that the MMR vaccine, along with most childhood vaccines in the U.S., contain no thimerosal or mercury. Furthermore, science has debunked the link between vaccines and autism. The correct option is 1.
Step-by-step explanation:
The correct response to the parents' concerns about toxic levels of mercury in the MMR vaccine is option 1) "Most U.S.-made vaccines have zero to low amounts of mercury." It is important to clarify that the preservative thimerosal, which contains ethylmercury, was removed or reduced to trace amounts in all childhood vaccines in the United States in 2001, except for some types of flu vaccines. Hence, currently recommended childhood vaccines, including MMR, do not contain thimerosal or mercury. It's also important to reassure parents that extensive research has shown no link between vaccines and autism.
Vaccinations, like the MMR vaccine, are critical in preventing outbreaks of diseases such as measles, mumps, and rubella. Despite claims to the contrary, scientific evidence systematically discredits the notion that the MMR vaccine causes autism. The resurgence of measles in various outbreaks highlights the ongoing need to maintain high immunization rates to protect against these once-common infectious diseases.