The inactivated vaccine developed by the China National Biotec Group (CNBG) affiliated with Sinopharm has been proved safe and effective in three-shot vaccination clinical trials among people aged three and above.
The CNBG said in a post on Weibo that data from phase I and phase II clinical trials done by it shows the three-shot vaccination plan produced more robust immune responses among volunteers than the two-dose plan, especially among people over 18 years of age.
There was no significant difference in the total incidence of adverse reactions among people above 18 following their second and third shots, according to the company. The most common local adverse reactions were pain, followed by erythema, swelling and itching.
The incidence of systemic adverse reactions was low, and there was no significant difference between the test and placebo groups. Common systemic adverse reactions were fever, fatigue and diarrhea, and the severity of adverse reactions was mild.
For volunteers between three and 17, common adverse reactions after their third shots were fever and pain at the injection site.
The post-vaccination geometric mean titer (GMT) is a key immunological parameter adequately expressing antibody response after vaccination.
According to the trial data, the group aged between 18 and 59 had an average neutralizing antibody GMT of 209.3 28 days after the second dose, and an average GMT of 308.4 28 days after the third shot.
For people above 60, the neutralizing antibody GMT was 118.2 28 days after the second dose and 206.2 28 days after the third dose.
The three-shot regimen also showed a more robust immune response than the two-shot regimen among volunteers aged 3 to 17.
The CNBG said that taking a third dose can better protect people against COVID-19 in the long run, though currently, it is more important to complete the two-dose vaccination schedule to reduce the risk of virus transmission and build an immune barrier.