A respiratory diseases expert at the university, David Hui, said they had studied 160 people who received the Sinovac jab, and found that half of them had low antibody levels a month after completing the two-dose regimen.
They’ve decided to give another dose of the Sinovac or BioNTech jab randomly to these 80 people, and 31 of them got their third dose on Wednesday.
Hui, who’s also a government adviser, said a low antibody level could mean reduced protection against a symptomatic infection. He told an RTHK radio programme that may be because the Sinovac jab is an inactivated vaccine.
But Hui said their research, which also included people who received the BioNTech jab, showed the two vaccines had a similar performance in terms of generating T cells, which can lower the risk of severe symptoms and deaths.
He said researchers will test their antibody levels in a month, and should be able to publish results in October.