"Mom, the place where the injection was given still hurts today." "I'm so sleepy, I'm going to sleep again." ...... Recently, more and more children aged 3-11 have been vaccinated against COVID-19, and these small "complaints" have often worried parents. Some children will also have a low-grade fever, which worries parents for two or three days.
These phenomena are said to be normal reactions to vaccination. Parents who know why they don't know why they are still muttering in their hearts: Why is the vaccine dose of the child the same as that of adults? What exactly is the normal reaction? On November 20, a reporter from Science and Technology Daily interviewed Zhang Yuntao, chief scientist of Sinopharm China Biologics, to clear up the confusion.
Why is the child so small, but the dose of vaccine is not the same?
Regarding children taking medicine, there was once a figurative saying: children take medicine and eat it. This is because the general child will take medicine less than adults, if there is a lack of suitable specifications of medicine, break a piece into small parts.
Most children now use their medications, halving or reducing the amount of medication for adults. However, in the vaccination of the new crown vaccine, it has been found that children aged 3-11 use the same dose of vaccine as adults. In fact, the doses and ingredients of the vaccine are exactly the same for all ages, including 3-11 years old, 12-17 years old, 18-59 years old, and over 60 years old.
If the small body carries the same dose of vaccine, will the child's body be "overloaded"?
The dosage of therapeutic drugs is either considered weight, and some also consider the surface area of the body, which is related to factors such as pharmacokinetics of drugs in vivo and liver metabolism.
"The mechanism of vaccines is different from that of therapeutic drugs, after the antigens in the vaccine enter the body, they are not directly metabolized, but are presented by the immune system, and the immune cells recognize and produce antibodies, and the antibodies then play a role in blocking viral infection or preventing the onset of disease." Zhang Yuntao said that the process of vaccine production of antibodies has no correlation with body surface area and body weight.
In fact, the vast majority of vaccine doses do not distinguish between adults and children. For example, there is no dose difference between hepatitis B vaccine, cervical cancer vaccine, and pneumonia vaccine.
"For example, infants are also given the IPV vaccine (injectable polio inactivated vaccine), and children who are young and adults are injected the same." Zhang Yuntao said that the use of a unified dose under the premise of ensuring safety is a global common approach.
In the course of clinical research, vaccine developers also conducted grouped trials of high, medium and low doses for adults and children, and found that the immune effect of different doses for adults and children was basically the same as that of the same dose.
"Currently used in medium doses, not in high doses, because medium doses are sufficient to stimulate effective immune protection." Zhang Yuntao concluded that the principle of dose determination of vaccines is to try to choose the dose that can achieve the most effective preventive effect under the condition of ensuring safety.
In addition, in the overall shortage of vaccines, based on cost considerations, some companies or organizations will call for a dose reduction to improve the accessibility of vaccines in the entire population.
The child's immune system is not fully developed, is the vaccine "full" effect?
There are also some parents who doubt that the child's immune system is still developing perfectly, but it is not fully developed, can vaccination play its due effect at this time?
"First of all, from the mechanism, after the vaccine enters the body of the child, the mechanism of producing antibodies is exactly the same as that of adults, there is no difference." Zhang Yuntao explained that secondly, although the child's immune system is still developing, in fact, children over the age of three are basically perfect, close to adults.
So, when the vaccine enters the human body, can it achieve the immune effect of "full grid"?
The answer is, close to full grid. This has also been confirmed by clinical trials in groups, where "immunogenicity" is a key indicator of the immune capacity of different populations.
According to the explanation provided by Baidu Encyclopedia, immunogenicity refers to the performance that can cause an immune response, that is, the antigen can stimulate specific immune cells, so that immune cells can be activated, proliferated, differentiated, and finally produce immune effector antibodies and sensitized lymphocyte characteristics.
"Judging from the research data of the new crown vaccine, the immunogenicity of the 18-59 age group is the best, followed by the age group under 18 years old, and the immunogenicity of people over the age of 60 is the worst." Zhang Yuntao explained that this is due to the degradation of various functions that occur with aging, which reduces the immunogenicity of the elderly, and the population under 18 years old is actually better than the elderly.
"But the difference is small, not particularly obvious, not statistically significant, so the vaccination strategy is the same for all ages." Zhang Yuntao added.
If you have to break the casserole, what is the difference in the immune systems of children and adults, and what differences will it bring?
"Our neutralizing antibodies are mainly produced by immune B cells in the body, and the proliferation and differentiation of this B cell in the child's body will be slightly limited and delayed; on the other hand, it is the auxiliary role in the whole system, including T lymphocytes and the ability or content of various factors involved in antibody formation that are slightly lower than normal..." Zhang Yuntao explained. Overall, it can be understood that the immune response is slightly weaker, but all within the normal range.
What does the most worrying issue for parents say in clinical studies?
Although vaccination has only recently been initiated among people aged 3-11 years, in fact, research on the vaccination of children has been carried out in parallel with that of adults.
According to reports, on April 12, 2020, the day that sinopharm Group China Biological New Crown Vaccine clinical trial was launched, two and three injections of the 3-17 age group were studied. Sinopharm China Bio also launched a systematic study of safety and immunogenicity for 3-17 years old in the UAE.
"Vaccines are approved for use at every age, and there is a strict approval process, which requires enough corresponding data to be approved for emergency use or marketing." Zhang Yuntao said that therefore, in the design of clinical trials, it is necessary to consider in advance to better serve the formation of the national immune barrier.
When conducting a comprehensive study on the emergency use of the new crown vaccine in the age group of 3-17 years old, the data required include data on neutralizing antibodies and safety data. "Safety data includes whole-body safety data and local safety data. For example, local pain redness and swelling, drowsiness, rare adverse reactions, and common reactions should be observed. Zhang Yuntao said that from the incidence of adverse reactions, the results of the study show that adults and children are the same, there is no difference.
The COVID-19 inactivated vaccine is a new vaccine, what are the new manifestations?
"If you are okay after half an hour of vaccination, there should be no serious adverse reactions." Zhang Yuntao said that after such a long period of vaccination, it was found that the child mainly had three reactions, one is a slight fever; the other is that the local area will be a little painful, because adults often feel less pain, children too small will be sensitive to pain; the third is a little drowsiness after partial vaccination.
In fact, with the modernization of production to bring about improvements in the vaccine production process, innovation brought about by the great improvement of technology, the entire research and development process of the new crown inactivated vaccine represents the current advanced level, so the adverse reaction rate will be lower.
"The safety data for children vaccinating against COVID-19 should be better than the safety data for other vaccines." Zhang Yuntao said that after years of development, the inactivated vaccine process is now very mature, and advanced automation control technology has been integrated. For example, the bioreactors used in the COVID-19 inactivated vaccine use more advanced control technology and a more optimized inactivation process to achieve more stable quality control, while in the purification step after the inactivation reaction, due to the use of more advanced purification techniques and materials, there are fewer impurities that may occur in the vaccine. These all provide an important material basis in terms of the safety of vaccine use.
So, what do children need to pay more attention to when getting vaccinated than adults?
At a press conference held by the Joint Prevention and Control Mechanism of the State Council, immunization experts said that in addition to understanding the process of new crown vaccination, they should also pay attention to the health status of their children. Do a good job of counseling, because children over 5 years old may have some psychogenic reactions, older children should avoid strenuous exercise, stay for 30 minutes, and if the vaccinated children have suspected adverse reactions, they should report in time. If there is overlap in time with vaccinations from other immunization programmes or non-immunization programmes, it is important to ensure that covid-19 vaccines are more than 14 days apart from other vaccinations.
Wen/Science and Technology Daily reporter Zhang Jiaxing
Editor/Fan Hui