The J&J vaccine is described here: Ad26.COV2-S (JNJ-78436735) Vaccine Description. Quoting,
AD26 is the specific strain of adenovirus. Quoting from AdVac ,
ADVAC® VIRAL VECTOR TECHNOLOGY
Adenoviruses are a group of viruses that cause the common cold – so they’re good for transporting things into humans.
(The “goodness” of the above has insufficient support for mass vaccination.)
Janssen’s AdVac® vectors are based on a specific type of adenovirus, which has been genetically modified so that it can no longer replicate in humans and cause disease.
While the details of manufacture are different, this shares the supposed “good idea” of the AstraZeneca and Russian vaccines, the use of a modified adenovirus to insert genetic material into cells at the injection site. The J&J vaccine now shares the distinction, with AstraZeneca, of trial halted by unexplained illness. See
- Why I Would Not Take the Russian or Oxford – AstraZeneca Vaccines – Part 2
- (CNN) AstraZeneca pauses coronavirus vaccine trial after unexplained illness in volunteer
- (CNN)NIH ‘very concerned’ about serious side effect in AstraZeneca coronavirus vaccine trial
With the halts of AstraZeneca and J&J trials, there is almost a pattern. An actual pattern is distinguished by one or both of:
- Frequency of occurrence.
- Specificity of syndrome.