https://www.clinicaltrialsarena.com/comment/covid-19-vaccines-antibodies-booster/

I wish to share an article that I found useful that disucsses the hurdles faced by the adeovirus based vaccines that are being generated to combat the SARS-Cov2 pandemic. Perhaps the most famous vaccine in this class is  azd1222 produce by a joint venture between Oxford University and AstaZenecca.

In summary it highlight the problem of using Adenovirus as a carrier to infect cells and introduce the human immune system to surface proteins of the SARS-Cov2 virus. Namely, adenoviruses already infect humans and most of the population has an immune responce to the adenovirus. So rather than develop an immune responce to the introduced SARS-Cov2 proteins, the body's immune system simply reacts and destorys the adenovirus.

This will be problem directly faced by CanSino whcih uses Ad5, a rather common and strongly immunogenic group of Adenoviruses. AstraZenecca attempts to avoid this problem by using Ad26, a different branch of the Adenovirus family, unfortunately the human immune response to this virus is markly lower and the virus is common in Africa. Hence boaster shots, space apart to maximum the immune responce will likely be required to attain immunity.