Let’s start with the big kahuna: Do vaccines actually work? The reality is: nothing’s perfect — and vaccines are no exception. Experts don’t actually claim that vaccines are 100 percent effective, just like they don’t claim that a medication or surgical procedure works 100 percent of the time. When administered properly, and with the recommended dosage and schedule, most childhood vaccines are between 80 to 100 percent effective. Even though these vaccines may not prevent all cases, they still have been shown to be protective.