During a recent winter immunization campaign, The Center for Disease Control and Prevention used the media to encourage all Americans to get vaccinated against the seasonal flu virus. This is an example of a $\_\_\_\_\_\_\_\_\_\_,$ where the media donated free space and air time.During a recent winter immunization campaign, The Center for Disease Control and Prevention used the media to encourage all Americans to get vaccinated against the seasonal flu virus. This is an example of a $\_\_\_\_\_\_\_\_\_\_,$ where the media donated free space and air time.