CoronaVac is safe and capable of eliciting a significant immune response against Covid-19 in children and adolescents. Results of recent clinical studies carried out in China, South Africa, Chile, Malaysia and the Philippines demonstrate that the immunizing agent from Butantan and the Chinese pharmaceutical company Sinovac represents no risk to young people aged between 3 and 17 years. So much so that China, Hong Kong and Chile, supported by the results of these clinical trials, have already authorized the use of the vaccine in this age group.
The World Health Organization (WHO) has already stated that all vaccines that have received permission from regulatory agencies in different countries to be applied to children and adolescents – such as CoronaVac – are safe and effective in reducing the burden of disease, but awaits the release of more data to authorize its use in the pediatric age group.
Since October 2021, 2,140 young people aged six months to 17 years have participated in a multicenter, randomized, double-blind, placebo-controlled study conducted in South Africa, Chile, Malaysia and the Philippines with CoronaVac.
The results of the safety data revealed that the incidence of adverse events after the second dose of CoronaVac was much lower than after the first dose. Local and systemic adverse events mainly involved pain at the injection site, headache and fever. There were no suspected and unexpected serious adverse events.
The study will provide a stronger scientific basis for countries to safely immunize their children and adolescents against SARS-CoV-2. Several nations, including Chile, Ecuador, El Salvador, Colombia, Cambodia and Indonesia, have already approved the use of CoronaVac for healthy people aged three to 17 years. In China, by the end of October, more than 110 million doses of the vaccine from Butantan and Sinovac had been administered to children under 18 years of age.
Vaccine most often used in the age group from three to 17 years old
Phase 1 and 2 clinical trials carried out in China and published in the scientific journal The Lancet Infectious Diseases have already demonstrated that CoronaVac is safe for the population aged three to 17 years and can induce a strong production of antibodies in this age group. The randomized, controlled, double-blind study evaluated 550 children (71 in phase 1 and 479 in phase 2) who took two doses of CoronaVac 28 days apart.
One group received the vaccine, while the other received a placebo with aluminum hydroxide, an adjuvant that is not harmful to the organism and present in the immunizing formula. The analyses showed that the vaccine was able to generate antibodies in 96% of the volunteers 28 days after the second dose. In phase 1, none of the participants had neutralizing antibodies against SARS-CoV-2 and, 28 days after vaccination, 100% of them had antibodies.
In phase 2, some volunteers received two administrations with smaller doses (1.5 µg) and others received larger doses (3 µg). While 95% of participants in the first group had antibodies in their blood, this number was 100% in the second group. Therefore, the researchers chose to go with only the highest dosage in the phase 3 clinical trial.
Adverse reactions ranged from mild to moderate, with pain at the administration site and fever being the most common, with symptoms disappearing within 48 hours. 27% of participants reported side effects. There was only one case of a serious adverse event not associated with the vaccine - one child had pneumonia after receiving a placebo.
Mild adverse effects
The biggest argument in favor of using CoronaVac in children and adolescents is the inactivated virus technology through which the vaccine is made.
One of the most traditional and studied in the world, it determines that the immunizing agent carries a dead virus, that is, inactivated, which is not capable of causing harm to human beings. In addition, scientific studies have already shown that CoronaVac is the vaccine that causes the least and mildest adverse events among all immunizing agents currently in use in Brazil.
“CoronaVac is the safest vaccine for use in children and adolescents aged between three and 17 years”, said Dimas Covas, president of Instituto Butantan. “It is the vaccine that has been most used in this population in the world. Today, we are close to 70 million children and adolescents vaccinated with CoronaVac”, he added.
Importance of vaccinating children and adolescents
In its "Interim statement on COVID-19 vaccination for children and adolescents", published on 29/11, the WHO pointed out the advantages of vaccinating children and adolescents against Covid-19 without failing to mention that the decision must take into account epidemiological issues and access to vaccines in each country.
According to WHO, vaccination against Covid-19 can reduce transmission from children and adolescents to older adults and thus help reduce the need for mitigation measures, including in schools.
Several risk factors for severe Covid-19 in children have been reported recently, including obesity and preexisting illnesses such as type 2 diabetes, asthma, heart and lung disease, and neurological and neuromuscular conditions, which can be taken into account in vaccination campaigns.
A systematic review suggests that there may be a greater impact of Covid-19-related pediatric fatalities in low- and middle-income countries compared to high-income countries, which may also influence the inclusion of children in Covid-19 vaccination, according to WHO.
However, the low rate of serious cases and deaths from Covid-19 in young children prevents them from being considered a priority in vaccination. Between December 2019 and December 2021, children under the age of five accounted for 2% of cases (1.9 million) and 0.1% of deaths (1,797) by Covid-19 reported globally.
Older children and younger adolescents (5 to 14 years) accounted for 7% of reported global cases (7, 058,748) and 0.1% of global deaths (1,328), while older adolescents and young adults (15 to 24 years) accounted for 15% of global reported cases (14,819,320) and 0.4% of reported deaths (7,023). Deaths in people under the age of 25 accounted for less than 0.5% of reported global deaths in WHO data.