The request comes days after Pfizer-BioNTech, makers of the other Covid mRNA vaccine, also requested emergency approval for a second booster shot, but their request was limited to adults aged 65 and older.

However, a paediatric infectious disease expert says it's not surprising that protection against mild illness would wane and that the goal of the vaccine is to protect against severe illness.

But researchers say people should still get vaccinated with Sinovac if there is no other option because some protection is always better than none.

Doctors could not explain the cause of Patricia’s problem but anti-vaccination groups went viral with it.