In human history, infectious diseases have been an important factor in the sharp decline of the population. In the field of infectious disease prevention and control, in terms of reducing morbidity and death, apart from safe drinking water, no medical strategy is more effective than vaccination.
Vaccination is one of the most cost-effective health investments. It is a proven method to control and eradicate infectious diseases. It is estimated that 2 to 3 million deaths can be avoided every year. In developed countries, deaths from infectious diseases account for only 4% to 8% of the total deaths, mainly due to the widespread use of vaccines. In developing countries, 30% or even 50% of the total deaths are still caused by infectious diseases.
With the development and application of various vaccines, traditional infectious diseases such as polio, measles, rubella, mumps, rabies, pertussis, diphtheria, tetanus, hepatitis B, and yellow fever have been well controlled. For example, after the application of live attenuated polio vaccine (OPV) in 1962, in August 1994, the Americas achieved the goal of being polio-free; in October 2000, the Western Pacific Region declared polio-free; October 2001 , my country announced the elimination of polio.
Where is the “sacred” vaccine
Before talking about vaccines, let’s first understand what immunity is.
Immunity refers to the process of the body’s reaction to antigenic substances including pathogens. Immunity includes innate immune response (non-specific immunity) and antigen-specific adaptive immune response (specific immunity) induced by antigen stimulation. For example, neutrophils, monocytes or macrophages in the human body belong to innate immunity. No matter what kind of pathogen invades, these cells will respond in the first time, start quickly, and fight the pathogen. The well-known antibody belongs to specific immunity, an antibody only works against a specific pathogen.
Vaccines are preparations intended to form specific immunity against a disease by stimulating the body to produce antibodies. Such as inactivating or attenuating microorganisms to make vaccines, or making certain components of microorganisms such as proteins and polysaccharides into vaccines. In addition, genetic engineering subunit vaccines have also been used maturely. In recent years, nucleic acid vaccines have gradually entered people’s field of vision as a new type of vaccine. Moreover, vaccines are no longer used solely for the prevention of infectious diseases, but also for treatment.
Vaccines against infectious diseases are cool
The basic way of vaccines against infectious diseases is: let the pre-prepared vaccine enter the human body through intramuscular injection, subcutaneous injection or inhalation, so that people will have immunity or resistance to certain infectious diseases. If you come into contact with the pathogen in the future, the vaccine Stimulate the body’s resistance to resist subsequent infections or diseases.
After entering the human body, traditional inactivated or attenuated vaccines, protein subunit vaccines, etc. can directly act as antigens to stimulate the human body to produce antibodies; while new nucleic acid vaccines such as mRNA vaccines enter the human body, they first synthesize proteins under the guidance of the genetic information they carry (Antigen), and then stimulate the body to produce corresponding antibodies.
Although we have been saying that stimulating the production of antibodies by vaccines is the key mechanism for vaccines to exert their protective effects, antibodies are not the only mechanism for specific immunity. In addition to directly inducing the body to produce antibodies, vaccines can also allow immune cells to produce memory. Once a pathogen invades, it will be activated and mobilize immune cells to produce antibodies. Moreover, the cellular response induced by the vaccine secretes many immune molecules, which also has a clearing effect on invading pathogens.
It takes a few steps for the vaccine to be applied to humans
A new vaccine needs to go through pre-clinical trials (animal trials), phase 1 clinical trials, phase 2 clinical trials, phase 3 clinical trials and post-marketing evaluations from research and development to clinical application.
After the vaccine animal test is determined to be safe, it can enter the human phase 1 clinical trial stage. At this stage, the safety of the vaccine is mainly observed, and the immune response of the human body to the vaccine is also observed.
If the safety assessment of the vaccine at this stage is passed successfully, it will enter a phase 2 clinical trial, during which a more extensive clinical assessment will be conducted, mainly to assess its effectiveness and safety.
If the Phase 2 clinical trial passes the review, it will enter the Phase 3 clinical trial. This stage is a bit like a “challenge trial”, which involves conducting clinical trials on thousands or even tens of thousands of people to evaluate the effectiveness of the vaccine. When the effectiveness is high enough and there are no obvious adverse reactions, the manufacturer or R&D institution can apply for the listing.
After the market is launched, the effectiveness and safety of the vaccine must be evaluated on a larger scale to provide a basis for the improvement or improvement of the vaccine.
Regardless of the stage of the vaccine, safety assessment will always be the first priority, and medical ethics must be strictly followed. Vaccine clinical trials can only be started on the premise of voluntary principles and full informed consent. To ensure the safety of subjects during the test, strict quality management and control measures must be implemented at each step of the test, and they must be able to withstand verification.
A little pain and tired, how to deal with adverse reactions
Adverse reactions occur after vaccination, some are caused by the protein or antigen in the vaccine, and some are caused by adjuvants and other auxiliary materials. Adverse reactions to vaccination include general reactions and abnormal reactions. Some reactions are rapid, such as acute allergic reactions, which can occur within 30 minutes after vaccination; a few may be delayed, such as 7 to 14 days after vaccination.
General reactions General reactions include local reactions and systemic reactions, such as local mild swelling and pain, systemic reactions such as fever (generally fever below 38.5 ℃, rarely more than 2 days), general discomfort and so on. The general reaction usually does not require special treatment, just drink plenty of water, pay attention to rest, and pay attention to the changes in the condition. Most people get relief within 48 hours after vaccination.
Abnormal reactions Abnormal reactions include local infections, aseptic abscesses, fainting needles, skin rashes, angioedema, anaphylactic shock, and systemic infections after vaccination. In order to prevent or reduce the occurrence of abnormal reactions, you should explain to your doctor whether the individual is not suitable for vaccination before vaccination, rest in the hospital after vaccination, and observe for 30 minutes before leaving if there is no abnormality. If fever or headache occurs, appropriate antipyretic analgesics can be given to relieve symptoms. If the local redness and swelling continue to expand, and high fever, you should go to the hospital for timely diagnosis and treatment.
In the practice of vaccination, some adverse events unrelated to the vaccine itself are mistaken for adverse reactions of the vaccine. For example, the vaccinator was originally infected with a certain pathogen, or the original underlying disease occurred just after vaccination. These are incidental diseases.
It should be noted that whether it is an adverse reaction of the vaccine itself or a concomitant disease, judging it is a relatively complicated professional process.
Vaccination for yourself, for everyone
Smallpox is currently the only infectious disease that humans have eliminated. On the one hand, some traditional infectious diseases still exist and prevail, and some infectious diseases that were once well controlled have revived; on the other hand, new infectious diseases continue to appear.
70% to 80% of the current epidemics are caused by viral infections, but the types of antiviral drugs are limited and there is a lack of specific antiviral drugs.
The prevention of viral diseases mainly depends on vaccines, but the enemy cannot be underestimated. Because, even though viral diseases have been vaccinated and prevention is very effective, due to the decline in vaccine coverage, outbreaks are still occurring in some countries and regions.
Many people believe that vaccination must be 100% protected from infection, otherwise it means that the vaccine is ineffective, thus negating the role of the vaccine. Since the birth of the vaccine, no vaccine has achieved 100% protection. Even if infection cannot be avoided after vaccination, due to the specific immune response induced, it can still reduce the incidence and reduce the severity of illness. This is a result that has been confirmed since the advent of the vaccine. This is especially important for people who are prone to severe illness after infection.
There are also many people who think that since 85% or 90% of people can build a population immune barrier after being vaccinated, I don’t need to fight it. I just need to be 10%. In fact, it takes a certain amount of time to build an immune barrier. Only when people who meet the vaccination requirements are vaccinated can an effective barrier be established and the spread of infectious diseases can be controlled. This is especially true for responding to emerging and emerging infectious diseases. The faster an effective immune barrier is built, the faster it can reduce or even block the spread, and it will prevent the spreading virus from adding mutations to escape the immune space.