Sinovac vaccine Photo: VCG

A real world study in Chile showed that CronaVac, the Chinese COVID-19 vaccine manufactured by Sinovac, can effectively protect children aged between 3 and 5 from infection, hospitalization and intensive care unit admission amid a rampant wave of the Omicron variant.  

According to the study, a preprint of which was published on Tuesday on Research Square, the estimated effectiveness of the CoronaVac shot was 38.2 percent against infection, 64.6 percent against hospitalization, and 69 percent prevention of intensive care unit admission.

The effectiveness was modest but protection against severe disease remained high, read the preprint report.

It is the world's first published data on the protective effects of the new coronavirus inactivated vaccine in children aged 3 to 5 and a study on effectiveness of the vaccine for this age group after the Omicron variant ravaged the world, Sinovac said in a statement on Wednesday.

The study is conducted by Chilean researchers from the Ministry of Health of Chile. It lasted from December 6, 2021, to February 26, 2022, and focused on the outbreak of the Omicron variant in Chile. Researchers said they did not estimate the vaccine effectiveness against fatal outcomes because only two deaths were observed in the unvaccinated group on February 26, 2022.

Chile started to vaccinate children aged 3 to 5 on December 6, 2021, according to Sinovac.  

The outbreak of the Omicron variant has caused an unprecedented number of COVID-19 cases, including many pediatric hospital admissions. Policymakers urgently need evidence of vaccine effectiveness in children to balance the costs and benefits of vaccination campaigns, but the evidence is sparse or non-existing, read the preprint report.

Leveraging a population-based cohort of 490,694 children aged 3 to 5, the Chilean researchers estimated the effectiveness of administering a two-dose schedule, 28 days apart, of CoronaVac using inverse probability-weighted survival regression models to calculate hazard ratios of complete immunization over non-vaccination, accounting for time-varying vaccination exposure and relevant confounders. 

A previous study in Chile on children aged 6 to 16 showed that the efficacy of two doses of CoronaVac for the group against infection with novel coronavirus was 74.5 percent, 91 percent against hospitalization and 93.8 percent against intensive care unit admission, according to Sinovac.

These results in Chile and the large-scale vaccination data of 260 million doses of CronaVac in the global population of children and adolescents demonstrate the safety and efficacy of the vaccine for minors aged 3 and above. In particular, it is very effective in preventing hospitalization and severe illness caused by infections in children and adolescents, Sinovac announced.