Sinovac Biotech’s Covid-19 vaccine may not trigger sufficient antibody responses against a new variant identified in Brazil, according to a small-sample lab study, Reuters reports.

Although the study suggests re-infection may occur in vaccinated individuals, the protection given by CoronaVac against severe Covid-19 may indicate other mechanisms in the human immune system, aside from antibodies, may also contribute to reducing disease severity, researchers said.

A Sinovac spokesman was not immediately available for comment. Chief executive Yin Weidong said in a programme aired by state-backed broadcaster CGTN on Thursday that the company was “fully capable” of using current research and manufacturing capacity to develop a new vaccine against variants if necessary.