Booster shots are being given in many countries, but other nations are not yet able to give their citizens a first dose.The immune response that can be achieved by administering Covid-19 booster shots at a reduced dosage is to be assessed in an international trial, in a bid to maximise global vaccine supply.
It said that trial participants would already have received two doses of Pfizer-BioNTech, Oxford-AstraZeneca, Sinovac or Sinopharm Covid-19 vaccines, depending on their location. In the trial, they will be vaccinated with either a full or reduced third dose of Pfizer-BioNTech, Moderna or Oxford-AstraZeneca vaccine.
Unpredictable supply of vaccines, or of the same vaccine product, is cited as a common reason for mix-and-match vaccination. The year-long study could offer countries realistic guidelines and a long-term solution regarding boosters, he said. Chinese regulators at the weekend said they had approved the mixing of domestic vaccines as boosters to improve immunity, and added two more Chinese-developed shots to the booster roster.