Vaccines are a critical component of our anti-infectious disease strategy. In addition to pathogen-specific immunogens, vaccines often contain variety of  preservatives,additives or adjuvants. The preservatives  helps in preventing microbial growth,The Adjuvents such as aluminium salts help in enhancing antigen-specific immune responses and additives such as gelatin helps in stabilizing live viruses. It may also contain byproducts of substances used during its production.

The amount in which these ingredients are used is considered safe and each of them serves a specific intent but,some ingredients are considered harmful if present in high amount. Also ,these ingredients helps in certifying its effectiveness.


Many of the components of vaccine are present in the human body. Many vaccine, for example, contain salts derived from sodium and potassium , which are vital for health. Although most people think it is an artificial chemical and found in minute amounts in the blood naturally.

These components are existing in trace levels, and no indication has been observed that these concentrations can lead to any damage. The limited percentage of individuals who seem to be hypersensitive to these components, even if it is existent only in low concentrations, is an exception . If you observe some vaccine components closely on the internet, you may notice that they are potentially hazardous, however maximum of them are often present in vaccines in quantities that are perfectly safe for human bodies. Even salt , which is required for regular biological function, is toxic in excess quantities.


As ,Each component of vaccine aids a specific purpose so the vaccine ingredients are used during production, help in providing resistance against a particular disease as well as keeping it safe and long lasting .


Antigens are the constituents derived through structure of infection-causing organisms, which are regarded as ‘foreign’ by the body’s defenses and stimulates a defensive immune response to the vaccine.

 In vaccines they are considered as active ingredients because they cause the body’s immune system to respond and develop defensive antibodies specific to that antigen. Antigens are either destroyed, weakened or artificially manufactured versions of the disease-causing organism or parts of the organism.

Individuals with weakened immune systems should not get live vaccinations because they may acquire the disease that the vaccine is designed to prevent.


Thimerosal is a mercury-containing chemical compound. It is often used in the preservation of a variety of pharmaceutical drugs. It also protects against life-threatening contamination driven on by dangerous bacteria.It is used as a preservative in multi-dose vials of flu vaccinations, and it is also utilised in the production process of two related children vaccines.

When separate doses are taken from the multi-dose vial, the preservative thimerosal prevents contamination. Thimerosal is added to vials which contains multiple doses  to prevent pathogens like bacteria and fungus from multiplying. When a syringe needle is inserted into a vial while preparing a vaccine for delivery, microbes and fungus can be introduced.

 Contamination of a vaccine by microorganism may result in severe inflammatory response, acute illness, or death. these preservatives  are added to some vaccines during the production process to inhibit microbial development.The kind of mercury present in certain types of fish is methylmercury. it  can be harmful to humans at high amounts of also includes ethylmercury, which is eliminated from the human body faster than methylmercury and so has a lesser risk of damage.

Aluminum salts

Even though we intake aluminum-containing foods and beverages on a daily basis, only a small quantity of aluminium enters the bloodstream during digestion; the remainder is excreted in the form of faeces. The kidneys processes and eliminates the majority of the aluminium in our bloodstream through urine.

In general, the use of aluminium adjuvants in vaccinations results in the requirement for less antigen or, in the case of certain vaccines, fewer doses.The use of aluminium salts in vaccines has a long and successful track of safety. Local responses and, less often, the formation of subcutaneous nodules at the injection site have been linked to aluminum-containing vaccine in some studies. This is especially true if the injection is administered too near  the skin’s surface.

An evaluation of all known trials of tetanus, pertussis and diptheria vaccine containing aluminium salts found no evidence that aluminium salts in vaccines cause major or long-term adverse effects.

Sugars and Gelatin

Gelatin is derived from pigs and works as a stabiliser to protect living viruses from the effects of temperature. There have been a few reports of adverse response to vaccine containing gelatine in about one case out of every 20 lakh doses of vaccine.

Stabilisers inhibit chemical reactions in the vaccine as well as component separation or adhesion to the immunisation vial during transit and storage. Sugars like sucrose, amino acids like glycine, and amino acid salts, as well as partly hydrolyzed proteins, are all examples of stabilisers.

Egg protein

Frequently, vaccine producers utilise chicken eggs to develop an inactivated or live-attenuated vaccine, resulting in tiny quantities of egg protein in the vaccine.These vaccinations are refined after manufacturing to eliminate the culture components.

Even yet, certain remants of the culture may be left behind. People with severe allergies may be at danger as a result of this. In addition to most flu vaccines, egg protein can be found in the yellow fever vaccine. Even after taking the appropriate precautions, the danger of acquiring the flu or yellow fever nearly always overcomes the risk of obtaining the appropriate vaccinations in persons with severe allergies.


Formaldehyde is a naturally-occurring substance already present in the human body as a part of normal metabolism(Approx. 42.52 grams ) and is used by scientists for killing live microbes in inactivated vaccines . Its concentration in large amounts of can be extremely toxic. Formaldehyde breaks down into its basic elements quickly both in the environment or once consumed by the human body thus preventing its accumulation.Also, its amount present in vaccines is a small portion of per day value found in humans.It is used to detoxify or deactivate the live microbe or toxin used in some vaccines and most of It is removed during the process of purification. It is required for the synthesis of DNA.


Vaccine safety and efficacy are under research. Safety testing is done as soon as a new vaccine is under consideration, continues until it is approved, and is then monitored permanently after approval. Some vaccine contain preservatives to protect them against  contamination by bacteria or fungi. The need for preservatives in vaccines emerged from a number of events in the early twentieth century in which patients acquired serious and most often lethal bacterial infections after receiving shots from multidose vials. In  vaccines, each component has a distinct function. These components has undergone thorough research and proven to be safe for people. Safety testing occurs as soon as a new vaccines are under consideration, continues until it is approved, and is then monitored permanently after approval.