Which of the following statements about vaccines is true?

The assertion that mild illnesses can occur in vaccinated individuals is accurate. Vaccines are designed to stimulate the immune system to recognize and respond to specific pathogens without causing the disease. However, it is possible for some vaccinated individuals to experience mild side effects, such as fever or soreness at the injection site, as a normal immune response. These side effects are usually short-lived and indicate that the vaccine is working to build immunity.

The effectiveness of vaccines varies, and while many are highly effective, none are guaranteed to provide complete protection for every individual. Furthermore, the notion that Thimerosal, a preservative used in some vaccines, has caused serious health effects is misleading; extensive research has shown it to be safe and non-harmful at the levels used in vaccines. Lastly, the concept that vaccines overwhelm the immune system is a misconception; vaccines are formulated in a way that is safe and helps the immune system to function more efficiently, rather than overwhelming it. Thus, the statement regarding the occurrence of mild illnesses in vaccinated individuals accurately reflects the reality of vaccine responses.