People who received two doses of China’s Sinovac vaccine were more likely to develop severe disease from COVID-19 than those who got two shots of the mRNA-based Pfizer-BioNTech or Moderna vaccine, a new local study has found.

“This supports the need for three doses of Sinovac-CoronaVac vaccine as a primary series,” the National Centre for Infectious Diseases and Ministry of Health said in a joint statement yesterday.

Researchers found that the Sinovac vaccine was 60 per cent effective against severe disease, compared with 90 per cent for the Pfizer vaccine and 97 per cent for Moderna’s vaccine.

In other words, people who took the Sinovac vaccine were more likely to require supplemental oxygen and intensive care, and also more likely to die of COVID-19.

The study involved 1.25 million people aged 40 and above inoculated with two doses of the Sinovac, Pfizer-BioNTech or Moderna vaccine. Of this group, 62,900 people eventually became infected with COVID-19 and 1,710 fell severely ill.

The authorities suggested that people who have taken two doses of the Sinovac vaccine should get either the Pfizer or Moderna vaccine as a third dose in their primary vaccination series. If not, they should get a third dose of the Sinovac vaccine.

“We will continue to monitor the vaccine effectiveness of the mRNA and non-mRNA vaccines, including how they are enhanced by a third dose or a booster dose,” the authorities said, adding that those offered booster shots should take them.

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