Why do we need a booster shot of the new crown vaccine?
2021-10-27
Many places in China have successively launched the new coronal vaccine booster immunization plan for high-risk people. The recent epidemic caused by the "tour group transmission chain" has made people pay more attention to this matter. Today, let's talk about the difference between basic immunization and enhanced immunization, and what role enhanced immunization can play in epidemic prevention and control. Difference between basic immunization and enhanced immunization In epidemiology, vaccination can be divided into "basic immunization" and "enhanced immunization". Basic immunization, as the name suggests, is the "full course" vaccination of a certain vaccine for the first time. For example, all kinds of vaccinations for children under 1 year old belong to basic immunization, and the first two doses of inactivated vaccine of new crown vaccine also belong to basic immunization. However, the times and doses of basic immunization of various vaccines are different. For example, basic immunization of BCG and measles vaccine only needs to be vaccinated once, while triple DPT vaccine and hepatitis B vaccine need to be vaccinated three times. The basic immunization times of different new crown vaccines are also different. The basic immunization of adenovirus vector new crown vaccine in China only needs one shot; Recombinant protein subunit vaccine should be vaccinated 3 times within half a year; The inactivated vaccine in China and the mRNA vaccine in the United States need to be vaccinated twice. Enhanced immunization refers to the re vaccination of similar vaccines after a period of time after the completion of basic immunization. The new coronal vaccine vaccinated by most people in China is inactivated vaccine. In this case, the third vaccination belongs to enhanced immunization. 2 "the third needle" how to improve immunity Why strengthen immunization? Over time, the body antibodies produced by people after receiving basic immunity will gradually decrease, and the immunity will gradually weaken. It is necessary to vaccinate again to improve immunity. The research data showed that the effectiveness of pertussis vaccine decreased from 100% to 84% in the fourth year after basic immunization, to 52% in the fifth year, and only 46% of people still had immunity in the seventh year. Therefore, after the basic immunization of DPT triple vaccine is completed within the age of 1 year, one shot of immunization should be strengthened at the age of 1 year, 6 months to 2 years, and one shot of DPT double vaccine should be strengthened at the age of 7 years. Similarly, the new crown vaccine is the same. A Belgian observation on the antibody of medical staff six months after vaccination with mRNA vaccine showed that the average level of antibody after the first vaccination was 100 units, the antibody increased to 400 units after the second vaccination, the antibody level remained at about 400 units after three months, but decreased to 221 units by the sixth month. When the body's immunity drops to a certain level, the resistance to COVID-19 will be weakened. After strengthening the immune system, it can not only significantly improve the body's antibody level, but also stimulate the immune system to produce more durable immune capacity and stronger immune memory. Therefore, it is very important for those who have completed basic immunization to strengthen immunization after a certain time. In addition, a small number of people with low immunity may not produce protective antibodies or insufficient antibodies after two doses of vaccine, which can also fill gaps and strengthen after the third dose of booster immunization. So, what is the actual effect of strengthening immunization? Let's look at the existing data. Israel is the first country to conduct large-scale immunization with the new coronal vaccine. In September 15, 2021, the new England Journal of Medicine published an article on the enhancement of immunization of the new crown vaccine in Israel. The results showed that the confirmed infection rate and the incidence of serious cases of the new immunization crowd were lower than that of the unvaccinated population by more than 9. The results showed that the infection rate and the incidence of serious cases of COVID-19 were higher. China's Kexing company and Sinopharm group have also published the effect of enhanced immunization with inactivated vaccine in China. The inactivated vaccine of Kexing company was inoculated with the third injection six months after the second injection. The antibody increased more than 10 times in one week and 20 times in two weeks. According to the data of the national drug group, the average titer of COVID-19 antibody was 209.3 after vaccination with second needles for 18 year old people aged -59, and the average antibody titer increased to 308.4 after vaccination with third needles. After the third vaccination, the average antibody titer increased from 118.2 to 206.2. All these data indicate that enhanced immunity can significantly enhance the body's immunity to COVID-19. Is it useful to face the mutated virus COVID-19 is constantly changing. The current popular COVID-19 transmission power is more than 2 times that of a mutant virus. It is infectious to varicella virus, or even more than SARS, smallpox, seasonal flu and other viruses. Therefore, some people worry that it is useless to have a reinforcing needle. For the mutant virus, the immune effect of the new crown vaccine may be reduced, but it is not ineffective. From May 2021 to June, the COVID-19 epidemic in Guangdong province of China was observed. The Guangdong Provincial Center for Disease Control and Prevention (DDC) observed the protective effect of the 2 vaccinated vaccine. The results showed that the protective efficacy of the inactivated vaccine against Delta COVID-19 was 70%, and the protection rate for severe COVID-19 infection was 100%. Those who were not vaccinated were almost immune to COVID-19. It can be seen that after strengthening immunity, the human body's resistance to the virus will also increase. 4 will the adverse reactions be more serious So, will strengthening immunity increase adverse reactions? Let's look at three sets of survey data. The United States approved the enhanced immunization plan of the new crown vaccine on September 21, 2021. According to the safety data of enhanced immunization of new crown vaccine in the United States on October 1, 2021, among 12591 people who completed the third dose of new crown vaccine, the reported incidence of local and systemic reactions after the second dose was 77.6% and 76.5%, while that after the third dose was 79.4% and 74.1%; The adverse reactions after vaccination are mostly mild or moderate, so it is considered that the new crown vaccine is safe to strengthen immunization. Israel's observation on the safety of new crown vaccine for the elderly with low immunity shows that the adverse reactions after the third vaccination are similar to those after the second vaccination. The common systemic reactions are fatigue, myalgia and fever, and the incidence is even lower than that after the second vaccination. The safety study of the third inactivated vaccine in China also showed that there was no significant difference in the total incidence of adverse reactions between people over 18 years old and those after the second vaccination. The most common local adverse reactions were pain, followed by erythema, swelling and pruritus; The main systemic adverse reactions were fever, fatigue and diarrhea, with a low incidence; The adverse reactions of 3-17-year-old people after vaccination were mainly fever and pain at the vaccination site. Most of the adverse reactions were grade 1, and no serious adverse reactions were found. 5 "reinforcing needle" is not the sooner the better Anyone can be immunized with the new crown vaccine. At this stage, China gives priority to vaccination to high-risk people, people over 60 years old and people with immune deficiency such as chronic diseases. But the time to strengthen immunization is particular. The research of Kexing company shows that the average neutralizing antibody level can only reach 45.8-49.7 when the third dose is injected 28 days after the second dose of vaccine; After 6 months of inoculation, the average neutralizing antibody level could reach 137.9-143.1. Therefore, the appropriate time for strengthening immunization of new crown vaccine should be 6 months after the completion of the second vaccination, rather than the earlier the better. Others asked: "must the vaccine for enhanced immunization be consistent with the vaccine for basic immunization?" the technical route of inactivated new crown vaccine from different manufacturers in China is the same. The use of vaccines from different manufacturers will not affect the immune effect or increase adverse reactions. In theory, it is also possible to enhance immunity with mRNA or adenovirus vector vaccine after inactivated vaccine. Due to the antigenicity difference of its immunity, it is likely to obtain better immune effect. Previously, some foreign students were vaccinated with mRNA vaccine abroad after being vaccinated with inactivated vaccine in China, and there were no adverse events. However, this conclusion still needs more clinical data to support. 6 do you want to play "the fourth needle" and "the fifth needle" in the future In the future, it is still uncertain whether it is necessary to play "the fourth needle" and "the fifth needle" and even make strengthening immunization the norm. However, researchers will timely adjust the way to strengthen immunity according to the changes of virus variation and human antibody level, and do not rule out the development of new and more effective vaccines for population immunization. In the current epidemic prevention situation, personal protection cannot be relaxed. Please keep these protection knowledge in mind. 1. Wear masks scientifically The mask shall cover the mouth, nose and chin, and the nose clip shall be compacted; If the mask is dirty, deformed, damaged or smelly, it shall be replaced in time. The cumulative wearing time of each mask shall not exceed 8 hours; Masks used in cross regional public transport or hospitals are not recommended to be reused. Note: don't wear masks up and down or inside and outside, and don't expose your mouth and nose when wearing masks. 2. Wash hands frequently When washing hands, try to use running water and soap or hand sanitizer. When there are no visible pollutants on your hands, rub your hands with hand disinfectant for 20-30 seconds. When going out, avoid touching the mouth, eyes and nose with unclean hands. 3. Observe the 1m line Keep a social distance of more than 1m when queuing, paying, talking, exercising and visiting. 4. Cover your mouth and nose when coughing When coughing and sneezing, cover your mouth and nose with a paper towel. When there is no paper towel, use your elbow instead. Don't throw the used paper towel into the dustbin. 5. Develop a healthy lifestyle Strengthen physical exercise, adhere to the law of work and rest, ensure adequate sleep and maintain a healthy state of mind; Healthy diet, smoking cessation and alcohol restriction; In case of discomfort such as fever and cough, seek medical attention in time. (author Cai Jiandong is a retired chief physician of Beijing Ditan hospital and deputy editor in chief of the Journal of adverse drug reactions)
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