"unlike other COVID-19 vaccine trials, the study lacked a comparison arm featuring serum samples from patients previously infected with the coronavirus, complicating the task of interpreting whether the response is likely to confer immunity."
It seems that a vaccine needing a 2nd booster jab is also something that is quite common.
Anyhow, good news all around... The more viable vaccines we have, the more likely that the pandemic will be controlled sooner.
https://www.fiercebiotech.com/biotech/sinopharm-shares-phase...
"unlike other COVID-19 vaccine trials, the study lacked a comparison arm featuring serum samples from patients previously infected with the coronavirus, complicating the task of interpreting whether the response is likely to confer immunity."
It seems that a vaccine needing a 2nd booster jab is also something that is quite common.
Anyhow, good news all around... The more viable vaccines we have, the more likely that the pandemic will be controlled sooner.