How are Covid-19 vaccine tests in children and adolescents?

How are Covid-19 vaccine tests in children and adolescents?
How are Covid-19 vaccine tests in children and adolescents?


With the start of vaccination against Covid-19 worldwide, the main concern was to protect those most at risk of hospitalization and death, such as the elderly, health professionals and people with chronic diseases.

The efforts of countries and vaccine developers have been focused on ensuring the effectiveness of their immunizers in the adult population. But in parallel, some vaccine manufacturers have also sought the safety and effectiveness of their immunizers in children and adolescents.For Renato Kfouri, pediatrician and president of the immunization department of SBP (Brazilian Society of Pediatrics), it is important to note that the licensing of vaccines for these age groups does not mean that they will be applied immediately. “The application of vaccines to adolescents may be interesting to protect those who are in a vulnerable situation, but as a routine strategy for healthy children and adolescents, we will have to wait longer,” he says.


This week, the first announcement came about how vaccines behave in this age group, and he was very positive: the Pfizer / BioNTech vaccine was 100% effective in adolescents aged 12 to 15 years.

According to the results of their combined phase 2/3 study in adolescents, which started on October 12, 18 cases of Covid-19 were detected among the 2,260 adolescents involved, all in the placebo group.

In addition to the efficacy data, the vaccine was also shown to be safe, with adverse events similar to those seen among those aged 16 to 25 years. The Pfizer vaccine was already being applied in the United States to young people aged 16 and over.

The company should start in the next few weeks another combined phase 1, 2 and 3 trial to test its immunizer on children between 5 and 11 years old and on babies from six months old, but there is, so far, no data on how many children are going participate in that study.

For Kfouri, as it is a vaccine used on a large scale, with a confirmed safety profile, the requirement to extend the age range of vaccines is smaller.

“As a vaccine that has already been applied to millions of people worldwide, [os testes] they do not need thousands of children, a minimum of six months of follow-up. If a preliminary safety data already exists and with verified immune response, this already accredits an extension of the age range more quickly. ”


The Chinese laboratory Sinovac announced on March 22 that its vaccine, Coronavac, is safe and induces an immune response in children and adolescents. Coronavac produced in Brazil in partnership with the Butantan Institute.

The preliminary results of the combined study of phases 1 and 2 with 552 children aged 3 to 17 years pointed to a good safety of the immunizer in two tested doses (one higher and one lower). In general, the reported side effects were mild, and two children who received the lowest doses had a high fever, according to the company.

Also according to the company, in children aged 3 to 11 years, the lowest dose induced immune responses in the form of production of favorable antibodies, while the highest dose worked well in young people aged 12 to 17 years.

The data have not been officially published in the form of a scientific article and have not been peer-reviewed.

These differences in immune response, explains Kfouri, occur because the immune system of younger children is still immature, while that of children and adolescents aged 12 and 13 is much more similar to that of youth aged 17 to 20 years.


The American biotechnology company Moderna started a combined phase 1/2 study at the end of 2020 with 3,000 adolescents aged 12 to 17 years, but the data has not yet been presented. The company recently started a new clinical trial with 6,750 children aged six months to 12 years.

The study was divided into two groups: the first will be without the double-blind factor, that is, both doctors and volunteers know who receives the immunizer and the placebo, in order to be able to assess what is the best dosage in children aged 2 to 11 years. The second should include children aged six months to two years to receive a vaccine of 25g, 50g or 100g per dose – at this stage, all children will be vaccinated.

In the next phase, the researchers will choose which dosages had the best response in children and will apply this dose in comparison to the control group.


Janssen, a pharmaceutical arm of Johnson & Johnson, has been testing its immunizer on individuals over 16 in the United States and Belgium.

In Brazil, Janssen states that it intends to carry out clinical studies to evaluate the effectiveness and safety of its single dose vaccine against Covid-19 in children and adolescents, but the protocols of these studies are still being evaluated by the competent regulatory agencies.

“The Janssen vaccine will be tested initially on a small number of adolescents that will be expanded to a larger group in a gradual approach, if the initial data demonstrates an adequate safety profile,” the statement said.


The University of Oxford announced in February that it will begin phase 2 studies in children and adolescents in the UK aged 6 to 17 years. The expectation is to evaluate 300 participants, of which 240 should receive the vaccine and the rest a placebo substance.

The study will be conducted at the University of Oxford and will also include three partner sites in London, Southampton and Bristol. Trial participants will be followed up for 12 months after the second dose of the vaccine.

The study organized and sponsored by the University of Oxford and funded by AstraZeneca and the National Institute of Health Research.

CanSino Chinese state-owned CanSino began testing its vaccine with a replicant viral vector (adenovirus 5) in 481 participants, including children aged six and older, to compare the safety and immunogenicity of two doses of the Ad5-nCoV vaccine in different age ranges. .

There is also a clinical trial using a viral vector of a lentivirus -type of viruses associated with neurological diseasesmodified with the genetic material of Sars-CoV-2 in individuals aged six months to 80 years old by the Shenzhen Hospital in China.

Data from these trials, however, do not yet predict when they will be completed.
Regardless of ongoing tests, there is still no provision for the inclusion of children and other groups – such as pregnant women and immunosuppressed people – to receive Covid-19 doses.

Ana Bottallo – Folhapress

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