A study conducted in Chile, during the outbreak of the Ômicron variant, with the evaluation of almost 500,000 children vaccinated with Coronavac, pointed out that the immunizer was 69% effective against hospitalizations in Intensive Care Units (ICUs), 64.6% in the prevention of hospitalizations and 38.2% effectiveness against infection by the new coronavirus.
The study results were published in preprint format, without peer review. Unlike efficacy trials, which pertain to studies conducted in controlled environments, such as those conducted during vaccine development, effectiveness data reflect the results of vaccination in practice in large populations.
In the analysis, the researchers included 516,250 children aged three to five years linked to the National Health Fund (Fonasa), Chile’s public health system. Of these, 490,694 received Coronavac, the remaining children, called the control group, did not receive the vaccine. For the study, children who tested positive for Covid-19 were excluded.
The children were immunized with two doses, 28 days apart, between December 6 and February 26. According to the research, “the estimates provide evidence of the effectiveness of vaccination in children aged three to five years during the Ômicron outbreak in Chile.”
The research group did not estimate the effectiveness of the vaccine against deaths because only two deaths were observed, being of unvaccinated children.
Evaluation of effectiveness
Previous studies have evaluated the effectiveness of vaccination with two doses of Coronavac in children aged six to 16 years, at a time when the highly transmissible Delta variant was the predominant strain of SARS-CoV-2 in circulation.
In that study, the estimated effectiveness of the vaccine was 74.5% for the prevention of Covid-19, 91% for the prevention of hospitalization and 93.8% for the prevention of ICU admission related to Covid-19. The estimates for the subgroup of children aged six to 11 years were 75.8% for prevention against Covid-19 and 77.9% for prevention of hospitalization for the disease.
Recent studies suggest that vaccines may be less effective against the Ômicron variant, but retain the ability to protect.
“We do not have data to assess whether vaccinated and unvaccinated children or their caregivers differ in some unobservable characteristics, such as compliance with Covid-19 protocols. Another limitation in our study concerns genomic surveillance capabilities,” the study described.
Source: CNN Brasil
