Children under 12 years of age are at low risk of becoming infected with SARS-CoV-2. In fact, in Spain, since the beginning of the pandemic, only 16 children under the age of 10 have died out of a total of 85,067 official deceased. In the United States, the figures are similar: 420 children under the age of 10 died out of a total of 653,000 deaths from covid-19.
These data reflect that the virulence of SARS-CoV-2 in children is very low. But it does not mean that they cannot be infected. What’s more, it is estimated that children account for 15% of current COVID-19 cases and that, to top it all, have high viral loads. Therefore, although the severity of infection in children under 12 years of age is low and most are asymptomatic, children can transmit the disease. Hence the importance of vaccinating them.
Everything indicates that, for those under 12 years of age, the mRNA vaccines of the Pfizer or Moderna companies will be chosen, approved for young people between 12 and 18 years old in May of this year. In fact, both pharmaceutical companies began the clinical trial in children between 5 and 11 years old in June. In total, they recruited 4,800 volunteers, of which 560 were Spanish, patients from the Hospital 12 de Octubre, the Hospital Clínico de Santiago, the IHP Centro de Especialidades Pediátricas de Sevilla and the Sant Joan de Deu hospital in Barcelona.
It is expected that at least Pfizer will communicate the results to the American drug agency during the months of September or October. If the evaluation is positive, it will be approved and examined by the European agency almost simultaneously.
The first thing is to calculate the immunogenic dose
What variables have been evaluated in the clinical trial with children? The first and most important variable has been the dose. Given that the age group between 5 and 11 years is very heterogeneous, it is important to calculate which dose is the most immunogenic, that is, the one that gave the greatest immune response to the vaccine antigen with the least side effects.
Three doses have been examined by Pfizer: the same as in adults, the one approved for the group between 12 and 18 years old, a third of this dose and a tenth.
The second variable is the side effects already described in young people or adolescents. There are mild ones, such as headache, muscle pain, chills, joint pain, low-grade fever, or pain at the vaccination site (usually the upper outer arm). But also serious, as possible miocarditis o pericarditis.
The first data from the volunteers at the Hospital 12 de Octubre seems very encouraging, with fewer side effects than adults and much milder.
When will the vaccination start?
What roadmap is contemplated? As the results of this clinical trial have not yet been sent to drug agencies, vaccination of the age group 5 to 11 years will not be before November or December of this year, with the beginning of 2022 being the most feasible date.
The good news is that, since vaccination protocols are in place for the young population and, after the success of their vaccination in our country – more than 75% of young people between 12 and 18 years vaccinated in a month –, it is foreseeable that the vaccination of children will follow the same pattern.
With these perspectives in mind several questions arise:
- Is it necessary to vaccinate this sector of the population to be protected as a society? Since the delta variant of the SARS-CoV-2 virus is two to three times more contagious than previous variants, such as alpha or beta; given that some data suggest that this variant may cause more severe disease than previous strains in unvaccinated people, and given that unvaccinated people remain the largest group of concern and that the highest risk of transmission is among unvaccinated people, yes it is pertinent to vaccinate children. Furthermore, if the forecast that to achieve group immunity it is necessary to vaccinate 90% of the population is true, it turns out that the group aged 5 to 11 years represents 11% (5 million) in Spain. To this is added that some scientists – especially those from the Oxford vaccine group – point out that the high transmission of the delta variant means that the vaccine is not preventing the transmission of this variant. Given that a total vaccination of the population could allow replicative virus levels will drop globally, there is no other option but to vaccinate the child population.
- What role does cross-immunity play in children who have recently received other vaccines? At first, it was believed that exposing children to many viruses could give them some natural cross-immunity to COVID-19. In other words, that the defenses and antibodies produced to combat other viruses could be “reused” for SARS-CoV-2 effectively. However, the reality is that children are neither less infected nor have a lower viral load than adults. His case does not appear to be one of cross immunity. The possible explanation for its different response may lie in innate immunity, which is the body’s first response to a pathogen. Children have been seen to have much higher levels of proteins responsible for innate immunity and increased expression of the genes that code for these proteins, which are called interferons and interleukins. The most direct conclusion is that what differentiates children from adults is their rapid innate immunity response to viruses, which takes much longer to establish in adults and is essential in COVID-19. The fact that vaccines in general also enhance the innate immune response suggests that vaccinating children can benefit by reducing the number of viruses in the general population and is another positive point to consider their vaccination.
In short, vaccinating children not only has more benefits than risks, but it will help us manage this pandemic in another way.
Carmen Alvarez Dominguez, Biochemist and molecular biologist, immunologist, vaccine expert and research professor in Health Processes at the Faculty of Education and Faculty of Health Sciences, UNIR – International University of La Rioja