还没有足够的时间诱导抗体对付新冠病毒（jj苗要至少15天）。必要时个人防护不可少。详见内链接。

https://www.npr.org/sections/health-shots/2021/03/04/973436193/got-questions-about-johnson-johnsons-covid-19-vaccine-we-have-answers

How long does it take for protection to kick in?

With all three vaccines, immunity builds over a few weeks after immunization. Data from Johnson & Johnson show that most vaccinated trial participants had a robust immune response 15 days after getting the shot, with significant protection reached by day 29.

 

 

你的朋友还没有充分免疫。