The study, sponsored by the vaccine developer, was conducted between Jan. 1 and Sept. 7 last year, before the Omicron variant was discovered. It is also yet to be peer-reviewed.
J&J said protection against infection from its single dose vaccine starts to wane only from the fourth month compared to the second month in the case of two-dose vaccines from rivals Pfizer Inc and BioNTech's as well as Moderna.
No waning of protection was found for ICU admissions for all the three vaccines, J&J said.
The company said the study was carried out by collecting claims and laboratory data covering 168 million people.
More about: coronavirus vaccine
