Sinovac’s senior director of overseas business, Weining Meng, said the studies showed the level of antibodies produced by their CoronaVac vaccine appears to drop off after six months.

However, the level of antibodies detected in recipients peaks at a higher level after receiving a third Sinovac dose than it ever reached during the initial course of immunisation, Meng said.

Even six months after the booster shot, the level of antibodies in recipients has been found to be higher than at any point after their second dose.

“After two doses, the body already has a memory of immunity, so when a booster is given we see both a high level of antibodies and a stable antibody (level),” he said at an online forum organised by Pharmaniaga.

“Even six months after the third dose, we see that the level (of antibodies) is still much higher than the peak after their second dose, so that is also encouraging for us.”

Meng said there appear to be benefits to waiting longer to administer booster shots, as the immunity reached when one is given after a year is more robust than that achieved after six months.

“We see that a longer (period before a booster) can induce a higher antibody (level),” he said, but added that it may not be practical for countries with serious outbreaks to wait a year to administer another jab.

“For countries still suffering high levels of Covid-19, people need to really consider a balance of early boosters or a later booster. Especially for the elderly and high-risk people, we still suggest the booster be given roughly six months after the second dose,” he said.

On vaccinating children, Meng said that their research has shown that their immunity seemed to be longer lasting than adults and the elderly, which suggests that boosters may only be needed much later when compared to adults.