Impact of vaccine pause due to Thrombosis with thrombocytopenia syndrome (TTS) following vaccination with the Ad26.COV2.S vaccine manufactured by Janssen/Johnson & Johnson on vaccine hesitancy and acceptance among the unvaccinated population.

Background: In response to reports of thrombosis with thrombocytopenia syndrome (TTS) post-vaccination, the Johnson & Johnson (J&J) vaccine was paused and then restarted in April 2021. Our objective was to assess whether this pause adversely impacted vaccine confidence.

Methods: Two large internet-based surveys were conducted in the US among adults to measure knowledge, attitudes and perceptions of the J&J vaccine pause and rates of vaccine hesitancy among unvaccinated persons before, during and after the pause.

Results: Among 66% of respondents aware of the pause, 44% identified blood clots as the reason for the pause without prompting. The impact of the pause on vaccine behavior among unvaccinated persons and perception of the vaccine safety system was mixed and modified by trust in the public health authorities. Those who were less willing to get vaccinated because of the pause were less inclined for all vaccines, not only the J&J product. Moreover, a notable proportion (22.1%) of the small number of persons (n = 30) vaccinated with the J&J vaccine after the pause reported not receiving information about the risk of TTS. The proportion of unvaccinated persons who were hesitant was increasing before and during the pause and then leveled off after the pause.

Conclusions: The J&J vaccine pause is unlikely to be a major barrier to vaccine uptake. Public attitudes about vaccines may be more resilient than appreciated, especially when safety issues are investigated with transparent communication. This paper has important implications for messaging and program administration with future vaccine-specific adverse events. Efforts may be warranted to ensure all persons being offered the J&J vaccine are made aware of the risk of TTS.