Anvisa approves Coronavac for children aged three to five years. Is it really necessary?

Last week (13/07) Anvisa authorized the emergency use of Coronavac — vaccine against Covid-19 by the Chinese company Sinovac produced in partnership with the Butantan Institute in Brazil — for children aged three to five years. Butantan’s request to the government agency had been in the pipeline since March. There is still no date for the use of the vaccine in the national vaccination plan of the Ministry of Health.

The dose for these children does not change in relation to that applied in other age groups. Vaccination considered complete consists of two doses spaced 38 days apart. In addition to Coronavac, the Comirnaty vaccine, from Pfizer, is authorized to be applied to children, but from the age of five. Unlike Comirnaty, however, Coronavac does not yet have full approval. In May, Butantan and Sinovac were given a period of one year to present sufficient evidence of the effectiveness of Coronavac — the deadline came with the end of the state of emergency due to the pandemic in Brazil.

A The health surveillance agency mentions seven sources to justify the decision, among them especially data on vaccination of children in Chile. Two months ago, Anvisa had informed that Coronavac was not yet approved for children aged three to five years due to insufficient specific data for them. In that rejection, Anvisa cited a low overall efficacy of the vaccine, of only 8% against symptomatic Covid. In a large sample of 55 a thousand elderly people in São Paulo, the effectiveness of Coronavac against deaths was 86 ,2%, and against symptoms was only 25%.

Gustavo Mendes Lima Santos, from Anvisa’s General Management of Biological Products, presented new data from Coronavac studies that persuaded agency directors to vote in favor of authorizing emergency use. One of the studies, which involved 17 a thousand children from six months to 17 years recruited in Chile, Malaysia, Philippines, Turkey and South Africa, separated these children by lot from those who received Coronavac or an inert product. Until the analysis, neither the researchers nor the patients knew what they received — a protocol called “double-blind”, to avoid the influence of biases.

The preliminary analysis of this study reached no conclusion on the efficacy. from Coronavac against deaths, as no children died in either group. Efficacy against the fever symptom was around 40%, with a high “margin of error” of around 5% to 65%. On the other hand, the effectiveness against hospitalization had a “margin of error” so large that it precludes conclusions.

Another study, which does not use the double-blind protocol, but was observational (meaning less rigor) involved more than 490 thousand Chilean children between three and five years old. It was funded by the Chilean Ministry of Health. The statistic that most caught the attention of Anvisa directors was the effectiveness of Coronavac against the hospitalization of children: 55,86%. The “margin of error” is between 38 and 68% , which points to a substantial degree of uncertainty.

It is necessary to vaccinate children against Covid-19?

For those people who are still concerned about possible unknown side effects from the Pfizer vaccine, the approval of Coronavac for young children could be good news from a perspective of its technology is the most time-tested—deactivating viruses rather than fat nanoparticles containing mRNA from a viral protein. Four medical entities consulted by Anvisa believe that the benefits of vaccinating young children with Coronavac outweigh the risks.

But this does not touch on another issue: Coronavac provides greater or lesser protection to children who natural immunity acquired from infection? Is vaccinating healthy children against Covid-19 necessary? Some countries such as Sweden have not adhered to generalized vaccination against this disease for children, preferring to focus on children with comorbidities.

An Israeli study, also observational and without peer review (as most of the Coronavac studies), calculated the effectiveness of natural immunity in more than 200 a thousand young people from five to 61 years: reinfection is avoided with an efficiency of 82, 5% (with a narrow “error margin” between 79,7 and 86,3%) up to one year after the first infection, remaining high for up to 18 months, the maximum period that the study followed. The study is by Tal Patalon and colleagues at Maccabi Healthcare Services in Tel Aviv, Israel.

The need to vaccinate healthy children against Covid-19 is a debate that is not over in medical science, as much as some science “influencers” and part of the press preach the opposite. In a March article published in a journal of the group British Medical Journal, Petra Zimmermann, from the Faculty of Science and Medicine, University of Fribourg, Switzerland, presents together with colleagues the pros and cons of vaccinating children in this case. The authors prefer to maintain neutrality, but conclude that “the argument for vaccinating all healthy children against Covid-19 is more difficult than for adults” because “the balance between risks and benefits is more nuanced. If Covid-19 remains a generally mild disease in vaccinated children and adults, it may not be necessary to vaccinate all children. ”.

However, Petra and colleagues continue, “children under the age of five probably need to be considered separately from children between five and 11 years old”. A new variant more worthy of concern among children could tip the scales towards vaccinating. In the case of developing countries like Brazil, where other endemic diseases can aggravate Covid, their opinion is that the threshold for vaccinating children may be lower.

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