Research shows that three doses of the Sinovac or Pfizer vaccine offer 98 percent protection against severe or fatal outcomes among adults aged 60 years or older.

A study involving over 20,000 COVID-19 cases ranging from mild to fatal in Hong Kong, China, found that two doses of either vaccine protected against severe disease and death among adults aged 60 years or older, with higher effectiveness with Pfizer (89.3 percent), compared with Sinovac (69.9 percent).

But the third dose of either Sinovac or Pfizer lifts the protection to about 98 percent.

Data editor: Zhao Hong

Graphic designer: Mukesh Mohanan