Study: Response of Unvaccinated US Adults to Official Information About the Pause in Use of the Johnson & Johnson-Janssen COVID-19 Vaccine. Image Credit: LookerStudio / Shutterstock

Has COVID-19 vaccine confidence dropped following the pause of Johnson & Johnson/Janssen?

A new study, which was conducted by Vishala Mishra and Joseph P. Dexter at Madras Medical College, Chennai, India, suggests that the infamous pause in the administration of the Johnson & Johnson (J&J)/Janssen coronavirus disease 2019 (COVID-19) vaccine, advised by the US Food and Drug Administration (FDA), has left doubt about the veracity of vaccine safety claims. This is a development that may have engendered vaccine hesitancy in a segment of the population.

Study: Response of Unvaccinated US Adults to Official Information About the Pause in Use of the Johnson & Johnson-Janssen COVID-19 Vaccine. Image Credit: LookerStudio / Shutterstock

A preprint version of the study (not yet peer-reviewed) has been released on the medRxiv* server.


The COVID-19 pandemic has left a trail of death, debility and economic devastation as it has spread worldwide. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – COVID-19’s causative pathogen – is rapidly and widely transmissible, triggering repeated global waves of infections. A significant minority that catches the virus will develop severe or life-threatening illnesses, with acute respiratory distress syndrome (ARDS), multi-system dysfunction or even death.

In the early stages of the pandemic, the only possible way to mitigate the unfolding crisis was an interruption of transmission, lockdowns, school and business closures, social distancing, hand and face hygiene, and the use of face masks in public were resorted to on a large scale. However, the costs of such measures were enormous in terms of economic disruption.

The emergency use authorization of the mRNA (messenger ribonucleic acid) vaccines, from Pfizer/BioNTech and Moderna, was a light at the end of the tunnel, indicating the possibility of containing viral spread and bringing an end to the imminent threat of the pandemic. Currently, over a score of vaccines are being administered all over the world, based on various platforms.

Following these, the FDA authorized the J&J-Janssen vaccine, eight million doses of which had been given within the USA by April 23, 2021. At this point, the fact that 15 women who had received this vaccine later developed thrombosis with thrombocytopenia syndrome (TTS) was considered important enough to recommend a temporary pause while the evidence for or against its safety and benefits was reviewed again.

The occurrence of the clots in a rare location (the cerebral venous sinuses), as well as in the large abdominal vessels or the deep veins of the leg, accompanied by low platelet counts, drew attention to them.

The review indicated that TTS is increased in incidence within the first two weeks post-vaccination. All previously reported cases were in women aged 18 to 59 years old. The rate of TTS was 7 per 1 million vaccinations among women up to age 50 and 0.9 per million thereafter.

In other words, TTS is a rare but real risk in women in this age group, and even less common in men or women aged 50 years or more.

The pause was lifted then lifted by both the FDA and the Centers for Disease Control and Prevention (CDC), stating that “the J&J/Janssen COVID-19 Vaccine’s known and potential benefits outweigh its known and potential risks.”

After such a pause, the top priority is to publish a united message targeted at restoring public confidence in the vaccine, by clearly communicating the findings and their implications. The occurrence of vaccine hesitancy has been clearly documented following a similar event, when the Oxford-AstraZeneca vaccine was temporarily put on hold in many European countries following a similar scare.

Information drives willingness

The current survey explored how unvaccinated adults in the US understood the pause, based on the information put out by the CDC on its online platform for the public. It was used in two cohorts (A and B) of adults between April 19-21 and 21-23, 2021.

The first cohort comprised only adults with neutral or negative feelings about COVID-19 vaccines. The first cohort read the CDC web page pertaining to the issue, prior to its updated version available on April 20, 2021, which was provided in text form to the second cohort.

Almost all participants correctly understood why the pause was recommended, the cause-effect relationship between the vaccine and the CSVT, and the characteristics of the vulnerable population.

However, the gap between the cohorts widened when it came to matters of mRNA vaccine safety and the rescheduling of canceled appointments. Again, less than 45%, vs. 70%, in the first and second cohorts, thought highly of the trustworthiness of the passage. Similar proportions thought it represented reliable evidence. And less than a fifth, vs. just over a quarter, in the two cohorts, said they would share it on social media.  

While both cohorts showed a similar grasp of the public information relating to the vaccine, it was obvious that with increased understanding of this matter, vaccine unwillingness decreased by 40% in cohort A and by almost half in cohort B.

Vagueness drives heightened risk perception

Interestingly, the “small number of reports” of cerebral venous sinus thrombosis (CVST) spoken of by the CDC web page was interpreted as meaning 100 or more cases by approximately 70% and 47% in cohort A and B, respectively. This is almost ten times higher than the 15 cases that were actually reported.

Again, a similar proportion of participants in the two groups estimated that ten or more deaths had followed vaccination, while one in three thought the vaccine would be paused for over two months.

About half the participants in either cohort said that they had less confidence that the J&J-Janssen vaccine was safe following the pause. However, about two in three, in both cohorts, said they did not think COVID-19 vaccines were any more or less safe following the same event.

Approximately three-fourths of the participants said they intended to take the Pfizer-BioNTech or Moderna vaccine.

What are the implications?

The misinterpretation of the number of cases of CSVT that led to the pause in the J&J/Janssen indicates the tendency to overestimate risk in matters of safety. This suggests that numbers should be provided to offer a concrete perspective of risk, improving decision making.

The fact of the pause, a very public event in the vaccine rollout in the USA, brought down public confidence in COVID-19 vaccine safety, which shows the problems associated with publishing some but not all information on risk during a pandemic intervention.

Though the passage was correctly understood, most participants said they would not share it on social media, indicating that messaging needs to be better targeted at unvaccinated adults and made available on platforms that are in wide use among them.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.


Journal reference: