What is a live attenuated vaccine?

Live attenuated vaccines should be used with caution in pregnant women, but the actual risk to the fetus remains theoretical. Many studies have shown that even if pregnant women (who do not know they are pregnant) receive the rubella vaccine, there is no increased risk of birth defects.

Live attenuated vaccines are produced from pathogens (either viruses or bacteria). These agents are attenuated (weakened), and there are various ways to reduce their potency, the most common being repeated culture with cell culture medium. or animal embryos (usually chicken embryos are used). The number of cultures can be up to 200 times, making the agent acclimatize to multiply in culture and reduce (or lose) its ability to multiply in human cell medium, ensuring safety to production of vaccines for human use.
For example, for the measles vaccine, the measles virus was isolated from a child patient in 1954, it took nearly 10 years of culture to create a live attenuated virus to make a vaccine.
To induce an immune response, a live attenuated vaccine must be able to replicate within the recipient's body. Therefore, the use of live attenuated vaccines is essentially the introduction of a very small dose of a virus or bacteria (reduced or attenuated) into the body, so that they multiply and form a population sufficient to Initiates the body's immune response. Any agent that acts on the vaccine (light, temperature, ...) or affects the multiplication process inside the body causes the vaccine to be reduced or ineffective (hence the live vaccine). attenuated vaccines require very strict storage and transport conditions, and places with limited equipment will not be suitable for the use of live attenuated vaccines).
The immune response obtained from live attenuated vaccines is almost exactly the same as in natural disease (live attenuated vaccines are the most effective immune response vaccines). However, some vaccines require a booster dose to reinforce the immune response.

In theory, the vaccine agent can be converted back to its original (full virulence) form, but this has only been observed in live attenuated (oral) polio vaccines. Although the vaccine multiplies in the body, the person using the vaccine will not get sick because the pathogen in the vaccine is no longer the same as the original. If the user is really sick, the disease is also much milder than the natural disease, and this is an adverse reaction of using the live attenuated vaccine.
In addition, live attenuated vaccines can cause more serious or life-threatening reactions, some of which stem from uncontrolled replication of the vaccine agent. (However, this only happens when the person receiving the vaccine is immunocompromised). Adverse reactions and risks with the use of live attenuated vaccines include:
The live attenuated agent reverts back to its original full virulence form and causes the same disease in the user as when infected. natural disease (very rare, and only seen in oral attenuated live polio vaccines). Normally the immune system initiates a response and eventually eliminates the live attenuated agent contained in the vaccine, but in immunocompromised cases, the immune response to a live attenuated vaccine is not In normal people, it is very easy to lose control of the live attenuated agent, allowing the agent to overreact and cause real disease. Persistent infections, such as with the BCG vaccine, can cause regional lymphadenitis, which is more severe than disseminated infection. If a live attenuated agent is cultured in a contaminated medium, it may be contaminated by other viruses (eg retrovirus with measles vaccine). In principle, live attenuated vaccines should be used with caution in pregnant women, but the actual risk to the fetus remains theoretical. Many studies have shown that even if pregnant women (who do not know they are pregnant) receive the rubella vaccine, there is no increased risk of birth defects. Some live attenuated vaccines are manufactured and marketed as lyophilized powders, which must be dissolved in the specified solution prior to use according to the manufacturer's instructions. At the same time, many live attenuated vaccines require refrigeration to ensure quality. If the technique of using the vaccine is not correct, the storage and transportation are not guaranteed, there is a very high chance that the vaccine will not bring about the expected effect, and more serious adverse reactions may occur to the user. .

Currently available live attenuated vaccines include measles, mumps, rubella, polio (oral), smallpox, chickenpox, BCG, typhoid (oral), yellow fever, rotavirus, and influenza vaccines. .
Vinmec International General Hospital uses a source of high-quality vaccines, of clear origin, suitable for the age to be vaccinated, ensuring safety from registration, storage to use.
Before vaccination, all children are screened before vaccination with pediatricians - vaccines to help children ensure the best health when vaccinated. The doctor will advise the family on the best preventive vaccines suitable for each age group according to the latest recommendations of the Ministry of Health & World Health Organization as well as how to monitor the reaction after vaccination. ask for. A team of experienced and professional pediatric doctors and nurses, understand children's psychology and apply effective pain relief methods for children during the vaccination process. 100% of vaccinated children are monitored and re-evaluated before leaving. Post-vaccination monitoring room is fully equipped with emergency facilities; the team of doctors - nurses are trained in anaphylaxis emergency management to ensure timely and correct treatment when an incident occurs. The vaccination room is airy, with a play area, helping children feel comfortable as if they are walking and have a good mentality before and after vaccination.

Article references source: WHO