Coronavac shows 64% effectiveness to avoid hospitalization of children

New research investigated the effectiveness (ie, real-life effectiveness) of two doses of Coronavac in children aged 3 to 5 years during the peak transmission of the omicron variant in Chile. To avoid symptomatic cases, the vaccine had a rate of 38%. For more serious cases, such as barring hospitalizations in ICUs, the effectiveness was 69%.

The study was published in the journal Nature Medicine. In total, more than 490,000 children aged 3 to 5 years made up the sample. Of that number, about 194,000 received two doses of Coronavac between December 6, 2021 and February 26, 2022, a period in which there was a high spread of the omicron in Chile. In addition, 189,000 children did not take any doses.

Another 106,000 minors took just one dose during the study break, but they did not make up the vaccine analysis.

In this way, the study compared the ratio of those who had the complete primary vaccination schedule with children who did not receive any dose. Scientists focused on three parameters: symptomatic Covid cases, hospitalization and ICU admission.

According to statistical analyses, Coronavac was 38% effective in preventing symptomatic cases, 64% in preventing hospitalizations and 69% in preventing ICU admissions.

The authors say that the result of the research indicates that the vaccine would be effective against Covid-19 among the little ones, even during the period of greater transmission of the omicron.

However, they also point out some caveats. One of them is that Chile focused its efforts on genomic sequencing of variants primarily for travelers from other countries, that is, it was not possible to have this precise information for the study sample.

It is also mentioned that the research was not able to assess how long the observed protection is maintained or whether it would be necessary to apply other doses in this age group. According to the scientists, further research needs to be done to ascertain these points.

Not authorized for minors

Unlike Chile, Coronavac did not have approval to be applied to children from three years of age in Brazil. The Butantan Institute, responsible for the vaccine in the country, filed a request with Anvisa to approve the use from this age group. The agency, however, authorized only for those over six years of age and asked the institute for more data.

In addition to Coronavac, only Pfizer in the country can be applied to children and adolescents from five years of age. Thus, children below that age cannot be immunized in the country.

Recently, the drugmaker reported that three doses of the vaccine for children aged 6 months to 5 years resulted in an immune response similar to two doses in young adults. In another randomized phase 3 study, the Pfizer vaccine was 90% effective among children aged 5 to 11 years.

However, the country has a low vaccination rate among minors – data show that more than half of them may be late for their second dose. Among the youngest, the situation is also slow, since only 30% of Brazilians up to 24 years old received the third dose.