The China-made Sinovac-CoronaVac vaccine is the least effective in preventing infection or severe symptoms among COVID-19 patients compared to the Sinopharm, Moderna, and Pfizer-BioNTech/Comirnaty vaccines, according to a recently published study from Singapore.
“We observed a lower relative effectiveness of two inactivated whole virus vaccines (Sinovac-CoronaVac and Sinopharm) against COVID-19 infection compared with two mRNA vaccines (Pfizer-BioNTech/Comirnaty and Moderna),” reported the researchers in a study published in Clinical Infectious Diseases on April 12.
Researchers said their findings imply Sinovac-CoronaVac and Sinopharm are 54 percent and 84 percent effective against severe cases respectively, “assuming the vaccine effectiveness against severe disease for Pfizer-BioNTech/Comirnaty of 90 percent as suggested by systematic reviews.”
Meanwhile, the study suggests that the Moderna vaccine is 96 percent effective in preventing severe symptoms among COVID-19 patients.
The researchers looked into infections and severe cases among a cohort of over 2.7 million people aged 20 and above, from 14 to 120 days after they had been vaccinated with two doses. Seventy-four percent of the cohort was vaccinated with the Pfizer-BioNTech/Comirnaty vaccine, 23 percent received the Moderna vaccine, while only 2 percent and 1 percent received the Sinovac-CoronaVac and Sinopharm vaccine respectively.
The study was conducted based on observations between Oct. 1 and Nov. 21, 2021, when daily cases in Singapore reached a peak, driven by the spread of the Delta variant. Ninety-six percent of the eligible population had received at least two doses of any vaccine by the end of last year.
The researchers found that people vaccinated with the Sinovac-CoronaVac were 2.37 times more likely to be infected by the CCP (Chinese Communist Party) virus, also known as the novel coronavirus, and 4.59 times more likely to develop severe symptoms compared to people who received the Pfizer-BioNTech/Comirnaty vaccine.
“Singapore study that showed five times the risk of severe COVID with Sinovac vs Pfizer. Thankfully only 2% vaccinated with Sinovac,” commented David Lye in a Twitter post on April 13. Lye, a coauthor of the study, is the director of the infectious disease research and training office at the National Center for Infectious Diseases (NCID).
By Cindy Liu
