The COVID-19 pandemic has imposed many communication challenges for public health authorities, especially communicating the safety, effectiveness, and importance of the COVID-19 vaccine. This study takes an integrative approach that includes a content analysis of COVID-19 vaccine-related messages from the CDC Facebook page and an experimental test of the effectiveness of the same types of vaccine-related messages on participants' attitudes toward the COVID-19 vaccine. Our findings from the content analysis show that gain-frame was used significantly more than loss-frame, and statistical evidence was more prevalent than narrative evidence in the CDC's COVID-19 vaccine-related messaging. Results from the experiment indicated that loss-framed, and messages with statistical evidence, may be more successful in promoting positive attitudes toward the COVID-19 vaccine.