by Taha Ali Khan

Vaccines play an important role in fighting a virus and creating immunity against it thus prolonging human life. But what do the vaccines contain that makes them effective against viruses and how are they developed? One of the key ingredients is antigen which is a tiny part of the disease causing bacteria that initiates an immune response so that the body can learn to fight the disease without getting sick. The antigen can be a small part of the disease causing bacteria such as a sugar or it can even be a debilitated version of the same. Preservative is another ingredient that is added to prevent the vaccine from spoilage once they’re opened for usage. The most common preservative used is 2-phenoxyethanol as it has little toxicity in humans.

Stabilizers such as sugars and amino acids are added to prevent any chemical reactions from happening within the vaccine and to also prevent it from touching the vial. Surfactants are added in the vaccine to prevent clumping and settling of the vaccine components within the vaccine itself by blending everything together. A Diluent, commonly sterile water, is used for diluting a vaccine to a correct concentration before it is consumed. An Adjuvent like aluminium phosphate, aluminium hydroxide or potassium aluminium sulphate is added in some vaccines to improve the immune response to the vaccine. Vaccines undergo evaluation and screenings in order to identify the correct antigen that will stimulate immune response. First the preclinical phase occurs where the antigen is tested on animals to grasp the knowledge of further disease prevention. Once the vaccine successfully initiates immune response in preclinical phase, the vaccine is tested on humans in three phases. In Phase 1, the vaccine is tested on a small group of young and healthy adult volunteers to confirm the immune response in humans. In Phase 2, the vaccine is given to several hundred volunteers having same characteristics as those people for whom the vaccine is being developed. Generally different age groups are evaluated here to check immune response in the respective age groups. In Phase 3, the vaccine is given to thousands of volunteers and then compared to a small group of people who weren’t vaccinated but acknowledged with comparator product to check the efficacy and safety in a much larger pool of people.

Once the results of the different trial phases are out and when the efficacy of the vaccine is deemed safe by different regulating bodies, the vaccines are distributed in an organized manner among the common people.

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