What Is an Attenuated Vaccine?

Live attenuated vaccine refers to the structure of the A subunit (toxic subunit) after the pathogen is treated with formaldehyde, and the toxicity is weakened, but the activity of the B subunit (combined subunit) remains unchanged, that is, a class that maintains antigenicity vaccine. Inoculating it into the body will not cause disease, but the pathogen can trigger the body's immune response and stimulate the body to produce specific memory B cells and memory T cells. Provides long-term or lifetime protection. Compared with inactivated vaccines (dead vaccines), this type of vaccine has strong immunity and long duration of action, but safety is a problem and it has a potential risk of disease (it may restore virulence in humans due to retrograde mutations). Belongs to the second generation vaccine.

Live attenuated vaccine refers to the structure of the A subunit (toxic subunit) after the pathogen is treated with formaldehyde, and the toxicity is weakened, but the activity of the B subunit (combined subunit) remains unchanged, that is, a class that maintains antigenicity vaccine. Inoculating it into the body will not cause disease, but the pathogen can trigger the body's immune response and stimulate the body to produce specific memory B cells and memory T cells. Provides long-term or lifetime protection. Compared with inactivated vaccines (dead vaccines), this type of vaccine has strong immunity and long duration of action, but safety is a problem and it has a potential risk of disease (it may restore virulence in humans due to retrograde mutations). Belongs to the second generation vaccine.

Chinese name

Live attenuated vaccine

Features

Vaccine has strong immunity and long duration of action

Belong to

Second generation vaccine

Used for

Live attenuated hepatitis A vaccine

Live attenuated vaccine I. Definition

Live attenuated vaccine refers to the pathogen that undergoes various treatments, mutates, and has reduced toxicity, but still retains its immunogenicity. Inoculating it into the body will not cause disease, but pathogens can grow and reproduce in the body, trigger the body's immune response, and play a role in obtaining long-term or lifetime protection.

Live attenuated vaccine

1. Induction of humoral and cellular immune responses, and some products: vaccination through natural infection routes can also induce mucosal immunity, allowing the body to obtain a wider range of immune protection.

2. Using live microorganisms, which can work in the body for a long time and induce a strong immune response.

3. Living microorganisms have the characteristics of re-proliferation. In theory, only a single inoculation is required to achieve a satisfactory immune effect.

4. May cause horizontal transmission, expand immune effects, and strengthen the herd immune barrier;

5.No need to add adjuvant;

6.The production process generally does not require concentration purification;

7. Low price.

Live Attenuated Vaccine III. Disadvantages

1. Generally, live attenuated vaccines retain some residual virulence, which may induce serious diseases in some individuals (such as immunodeficiency patients).

2. Due to various reasons (such as genetic modification, etc.), the live attenuated vaccine may appear "virulence return".

3. It is a living microorganism preparation, which may cause environmental pollution and cause cross infection.

4. Defective particles may interfere with the immune effect of the vaccine.

5. It is difficult to analyze and evaluate products.

6. The requirements for storage and transportation are high, such as the need for cold chain.

Live attenuated vaccine

General taboo

Patients who have used gamma globulin, immunoglobulin or other passive immunizations in the last 4 weeks should postpone the vaccination of live vaccines ^[1] .

Acute infectious disease incubation period, prodromal period, onset period and recovery period. Those with a previous history of an infectious disease need not be vaccinated, considering that they have acquired post-ill immunity.

Vaccination should be suspended for those who have fever (especially those with high fever), patients with acute illness, and severe malnutrition.

People with allergic constitution, bronchial asthma, urticaria, thrombocytopenic purpura, and food allergies cannot be vaccinated with this allergen.

Vaccination should be suspended for patients with active tuberculosis, cardiac compensatory dysfunction, acute and chronic kidney disease, diabetes, hypertension, cirrhosis, hematological disorders, severe chronic diseases, active rheumatism, and severe purulent skin diseases. vaccine.

2. Special taboos

Anyone who suffers from immunodeficiency disease, leukemia, lymphoma, malignant tumor, and the use of corticosteroids, alkylating agents, antimetabolites or radiation therapy, and splenectomy to suppress immune function should not use live vaccines.

Pregnant women, especially during pregnancy, cannot use live vaccines.

Epilepsy, rickets, encephalitis sequelae, convulsions and other neurological disorders and mental illnesses or previous medical history are forbidden to inoculate Japanese encephalitis vaccine, diphtheria vaccine and meningococcal polysaccharide vaccine.

After receiving diabetic vaccine, strong reactions such as collapse or shock, continuous screaming, body temperature exceeding 40 ° C, seizures or convulsions, severe changes in consciousness, systemic or local neurological symptoms, allergic reactions, thrombocytopenia, or hemolytic anemia, etc For severe abnormal reactions, subsequent vaccination should be stopped.

BCG vaccine should not be given to people with eczema, otitis media or other serious skin diseases, and those who have a positive tuberculin test.

Diphtheria toxoid and its mixed preparations are forbidden in patients with nephritis during recovery or chronic nephritis.

Live attenuated vaccines V. Common live attenuated vaccines

The live attenuated vaccines currently in clinical use are: live attenuated measles vaccine, live attenuated hepatitis A vaccine, lyophilized live attenuated hepatitis A vaccine, live lyophilized attenuated chickenpox vaccine, live attenuated Japanese encephalitis vaccine , Live attenuated rubella vaccine, live mumps attenuated live vaccine, oral polio attenuated live vaccine, oral rabies attenuated live vaccine, etc.

Live attenuated vaccines 6. Simultaneous vaccination with live attenuated vaccines

(I) Basic principles

1. China's regulations for simultaneous vaccination

The third part of the Chinese Pharmacopoeia (2010 edition) does not stipulate the general principle of simultaneous vaccination of two vaccines, but in the precautions for each live attenuated vaccine manual, some stipulate that the interval of simultaneous vaccination of two live attenuated vaccines 1 month.

The "Vaccination Work Specifications" issued by the Ministry of Health of China in 2005 stipulates that if two or more National Immunization Program (NIP) vaccines need to be vaccinated at the same time, they should be vaccinated at different locations as required. It is strictly forbidden to inhale several vaccines in a single syringe. If the two live attenuated vaccines are not given at the same time, they should be vaccinated at least 4 weeks apart.

2.WHO

The WHO's general position paper on vaccines states that if the vaccine is intended for use in infants or young children, it should be easily adaptable to the immunization procedures and timing specified by the NIP, and if used concurrently with other vaccines, it should not significantly interfere with these vaccines Immune response. And in its various vaccine position papers, based on the available scientific evidence, specific recommendations were made for simultaneous vaccination of 2 vaccines. For specific operations when receiving multiple vaccines at the same time, WHO and other international organizations recommend that if 2 vaccines are given, do not use the same syringe and do not inject the same upper or lower limbs at the same time.

3.US ACIP

Most widely used vaccines are given at the same time (ie, on the same day), including live attenuated vaccines and inactivated vaccines, and the resulting seroconversion rates and incidence of adverse reactions are similar to these vaccines when administered separately. It is recommended that children without special contraindications should be routinely vaccinated at all ages.

(2) Related suggestions

1. Live attenuated vaccines for measles, mumps (fluid gills), and rubella

Because Measles Attenuated Live Vaccine (MV), Mumps Attenuated Live Vaccine (MuV), Rubella Attenuated Live Vaccine (RV) are often vaccinated as a combined vaccine.

"Chinese Pharmacopoeia" three (2010 edition) provisions:

(1) MV, MuV, RV, measles-rubella combined attenuated live vaccine, measles-fluid cheek combined attenuated live vaccine: the use of other attenuated live vaccines and vaccination with these five vaccines should be at least 1 month apart Between the two vaccines, the live attenuated vaccines with different components can be vaccinated at the same time.

(2) Live measles-fluid-rubella combined attenuated live vaccine: The use of other live-attenuated vaccines and MMR vaccination should be at least 1 month apart.

WHO's recommendation:

MV alone or with other measles-containing Vaccine (MCV) vaccines can produce the same protection against measles. When MCV or other vaccines are given at different locations at the same time, such as Diphtheria Toxid (DT), Tetanus Toxid (TT), Pertussis Vaccine (PerV), type b influenza (influenza) ) Haemophilus Influenzae Typeb Polysaccharide Conjugate Vaccine (Hib), Oral Poliomyelitis Attenuated Live Vaccine (OPV) or Inactivated Poliovirus Vaccine , IPV), Varicella Attenuated Live Vaccine (VarV), Hepatitis B (Vaccine, HepB), 7-valence Pneumococcal Polysaccharide Conjugate Vaccine (PPCV7) The immunogenicity and reactivity of each vaccine component remains unchanged. Similarly, existing data suggest that MV, Yellow Fever Attenuated Live Vaccine (YFV), Japanese Encephalitis Vaccine (JEV) can be in different parts at the same time Inoculation. However, because it was found that the immune response of MV was slightly reduced after the simultaneous inoculation of JEV and MV, further research on the possible impact of simultaneous inoculation of JEV and MV on the effect of MV was encouraged.

When different combinations of Rubella-containing Vaccine (RCVV) vaccines (Rubella-containing Vaccine) were inoculated with other live attenuated or inactivated vaccines at the same time, the induced serological conversion rates were similar. RCV can be given at the same time as the inactivated vaccine. According to the routine, live attenuated vaccine should be given at the same time, or at least 4 weeks later. With the exception of OPV, OPV can be vaccinated at any time before or after MCV or RCV vaccination without interfering with the immune response induced by both. Mumps-containing Vaccine (MuCV) comes in three forms: MuV, MM, and MMR. WHO's position on the vaccine is that once MuV is included in the NIP, MMR is strongly recommended. Therefore, most countries use MMR to prevent gill flow, which is inoculated with other vaccines at the same time as MMR.

US ACIP recommendations:

The United States currently uses MMR and a combined measles-fluid-rubella-varicella live attenuated vaccine (Measles, Mumps, Rubella and Varicella Combined Attenuated Live Vaccine, MMRV). The ACIP recommends that MMR be used when a vaccine of any composition is needed. Neither theoretical considerations nor practical experience have shown that simultaneous administration of MMR and other attenuated or inactivated vaccines can reduce antibody responses or increase the incidence of adverse reactions.

American ACIP encourages children of appropriate age to routinely receive MMR, diphtheria-tetanus-acellular pertussis combined vaccine (Diphtheria, Tetanus and Acellular Pertussis Combined Vaccine, DTaP), diphtheria-tetanus-tetanus and whole cell pertussis combined vaccine , DTwP), Hib, OPV, or IPV. MMR and Hib and HepB were vaccinated at the same time, the antibody response was the same, and the incidence of adverse reactions did not increase significantly. Studies have shown that the simultaneous vaccination of MMR and VarV with the two vaccines is 6 weeks apart, and the serological conversion rate, antibody level, and incidence of adverse reactions are similar in the two groups ^[2] .

Live Attenuated Vaccine 7. Status of Live Attenuated Vaccine in China

China is a big consumer of vaccines, with one billion doses of vaccines vaccinated each year. Most of the vaccines developed in China are traditional vaccines such as monovalent vaccines and live attenuated vaccines, while most of the vaccines marketed abroad are mainly new vaccines such as combined vaccines and inactivated vaccines.

Compared with the international advanced level in terms of production capacity and key technologies, domestic vaccines still have a huge gap. Wang Yu, director of the China Centers for Disease Control and Prevention, pointed out in 2010 that China does not have a policy and system to promote the application of new vaccine technologies. China's vaccine production technology is updated very slowly, or even without updates, and it has continued to use production technology 30 years ago. Wang Yuedan, deputy director of the Department of Immunology at the Peking University School of Medicine, said that many domestic vaccines still use the technology of the 1960s.

The quality of some domestic vaccines is not up to standard, and the regulatory authorities lack a systematic review of these vaccines after their large-scale marketing. The quality of some vaccines does not meet the quality standards in large-scale populations. Compared with imported vaccines, the quality is much worse.

The Ministry of Health of China and the State Food and Drug Administration have formulated vaccine production and transportation regulations, emphasizing that too high or too low temperatures can cause changes in the biological characteristics of vaccines and change them, and stipulate the production, transportation, storage, and cold storage of vaccines before injection The chain temperature must have a complete and rigorous temperature record.

However, according to the Southern Metropolis Daily reported on June 24, 2013, the current status of domestic vaccine transportation is: "Equipment is basically equipped, but there are problems with supervision, and it basically depends on the sense of responsibility of the practitioners. The eight links in the cold chain are doing well. The key is that root nodes are prone to problems, especially at remote county and township levels, which cannot be guaranteed at all.

Internationally, strict and demanding standards have been set for the transportation and maintenance of vaccines. Taking the United States as an example, the regulations require that the time interval between the shipment of vaccines and the arrival of vaccines should not be greater than 48 hours. During routine storage of vaccines, the temperature of the refrigerator compartment should be maintained at 2 ° C-8 ° C, and the temperature of the freezer compartment should be maintained at -15 ° C or Lower. A large bottle of water should be placed in the refrigerator so that the temperature can be maintained when the refrigerator door is opened. In addition, some vaccines have special requirements in terms of storage. For example, measles, rubella and mumps vaccines should be kept away from light, while chickenpox vaccines should be kept frozen in addition to light. The person in charge of the vaccine storage site should also develop a written emergency plan to ensure the safety of the vaccine in the event of a power outage or mechanical failure.