Abstract
Background: Vaccine hesitancy has become a prominent public health concern, particularly within the coronavirus disease 2019 (COVID-19) pandemic context. Worries about vaccine side effects are often cited as a reason for hesitancy, while media reporting about this topic plays an important role in influencing the public's perspectives about vaccines and vaccination. In Vietnam, during 2012-2013, there were several adverse events following immunization (AEFIs) of Quinvaxem- a pentavalent vaccine in the Expanded Immunization Program, which made big headlines in the media. Such incidences have contributed to changes in vaccination policies and influenced parents' concerns to date. This study explores the portrayal of Quinvaxem in Vietnam digital news during four periods marked by important events. Methods: We performed quantitative and qualitative analysis with a coding framework to identify main content focus, sentiments towards Quinvaxem, and emotional tones in these articles. Results: In total, we included 360 articles into analysis. The amount of news coverage about Quinvaxem increased after AEFIs happened, from 7 articles before AEFIs to 98 and 159 articles in the following periods when AEFIs and investigation into vaccine safety occurred. Most articles are neutral in titles (n=255/360) and content (n=215/360) towards Quinvaxem and do not convey emotional expressions (n=271/360). However, articles focusing on side effects contain negative sentiments and emotional expressions more frequently than articles of other contents while AEFIs details were conflicting across articles. Vaccine sentiments are provoked in the information about vaccine quality and safety, health authority, local delivery, and quoted vaccine opinions. Emotion-conveying elements in 89/360 articles included emotional wording and imagery and expressive punctuation. Conclusions: The heterogeneity of information in online news may reinforce uncertainty about vaccine safety and decrease vaccine intention. Our results have important implications for vaccine communication, given the current plan of the Vietnamese government to roll out COVID-19 vaccination to younger children.