The year 2020 had been a very unusual year. Since March 2020, Covid-19 has taken over the world with thousands of cases of Severe Acute Respiratory Syndrome (SARS) from each corner of the world. However, the times are changing as the world is adapting to it and scientists around the world have been able to create the vaccine against Covid-19.
What is a vaccine?
A vaccine is a biological preparation of a causative agent of a disease which can be used as an antigen to induce active immunity inside body for protection against specific diseases.
A vaccine can be given intramuscularly, orally, subcutaneously, nasally or intradermally.
What is present in a vaccine?
For a vaccine to be safe and provide maximum efficacy, certain substances are added along with the active ingredient to ensure its stability.
Active ingredient
These are also called antigens. They enter the body and get sensitized by immune system. This leads to production of antibodies which later helps in fighting the actual disease.
Active ingredient can be of different types which vary with different infections which will be discussed later.
Adjuvant
Adjuvants are substances that are added to the vaccine to boost our immune response to vaccines. Thus, it helps in lengthening and strengthening the immune response.
Different types of adjuvants:
- 1. Aluminum salts such as aluminum hydroxide, aluminum phosphate or potassium aluminum sulphate.
- 2. AS04
- 3. MF59
- 4. AS01B
- 5. CpG 1018
Preservatives
Preservatives are compounds that provide protection from contamination against harmful microorganisms. As multi-dose vials are repeatedly used for vaccination, preservatives are mostly added to them.
The most common preservative is Thimerosal. Thimerosal is an organo-mercury containing compound that is used widely as antiseptic and antifungal agent. It contains ethyl mercury. There is no evidence found suggesting mercury toxicity due to thimerosal as methyl mercury causes toxicity and not ethyl mercury. However, concerning the safety of children against mercury toxicity, the use of thimerosal in reduced in vaccination for children as a part of precaution.
Other preservatives are phenoxyethanol and phenol. Phenoxyethanol is an aromatic ether alcohol and phenol is an aromatic alcohol.
Stabilizers
Stabilizers are substances which help to maintain the effectiveness of vaccine. It stabilizes the contents of vaccine during storage and transportation.
Temperature, pH, etc. can be factors leading to decreased antigenicity of vaccines. This leads to decreased immune response against vaccine. Hence, stabilizers are essential for preserving the antigenicity and effectiveness of vaccines.
Gelatin is a stabilizer used in some live vaccines. It is made by partially hydrolyzing collagen, usually of bovine (cow) or porcine (pig) origin. However, there can be a mild allergic reaction associated with use of gelatin. Use of gelatin in patients having anaphylactic response is contraindicated.
Other stabilizers are lactose, sucrose, glycine, monosodium glutamate, mannitol, polysorbate 80, etc.
Who can take the Covid-19 vaccine?
Different covid-19 vaccines have different rules and regulations regarding vaccine distribution and administration.
Nevertheless, people who are at high risk of exposure like frontline health workers are given the first priority. Then, people of old age who are having high susceptibility to infection are given vaccines. These are followed by the general population of age 16 and above.
The vaccinations for children below 16 years of age have not been recommended yet. This is due to the fact that very few children have been part of clinical trials of vaccine. Hence, there is less evidence and data regarding the efficacy and dose of covid-19 vaccine among children.
People with co-morbidities such as chronic diseases and pathologies in cardiac, renal, neurological, endocrinal, malignancies, etc. with stable conditions are also eligible.
Patients suffering from diabetes and hypertension are also eligible for vaccination.
People with HIV infection or immunocompromised people are also eligible for vaccination as they are at high risk but with precaution.
Is vaccine safe?
It is justified to question about the reliability of covid-19 vaccines especially in the pandemic. However, the WHO and governments around the world have legalized the usage of vaccines after extensive clinical trials.
Yes, there can be certain side effects like fever, headache, pain at site of administration, etc. in certain population but the advantages of vaccines far outweigh its side effects.
Why is vaccine important?
Till now around 100 million people worldwide have been infected with covid-19. Out of which, around 2 million people have died. This is the case of only 1 disease whose case fatality rate is considered quite low. Before SARS, there have been number of people who have died of numerous other diseases. All these diseases have been under control and some are eradicated due to vaccines such as smallpox, polio, etc. Today, vaccines provide protection against more than 10 diseases including hepatitis, polio, diphtheria, pertussis, tetanus, measles, etc.
Why 2 doses of covid-19 vaccine are needed?
Most of the Covid-19 vaccines require two doses. The efficacy of Covid-19 vaccine after the first dose is around 50%. After the second dose is given, its efficacy increases to about more than 90%.
The first dose helps the immune system create a response against Covid-19. The second dose further increases the immune response to ensure lifelong protection.
What are the side effects of Covid-19 vaccine?
Different vaccines can have different side effects. Covid-19 vaccines are associated with certain common side effects like:
- 1. Fever
- 2. Headache
- 3. Sore throat
- 4. Allergic reaction
- 5. Redness and pain at site of injection
- 6. Fatigue
- 7. Muscle pain, etc.
The frequency of side effects in people is quite less than the number of people receiving vaccines. These side effects begin within a day or two after vaccination and last for about 1-3 days and eventually subside. There is no need for medication for usual side effects as they show the antigenicity of vaccine which is required for a sufficient human response. Medication or hospitalization is required only in severe allergic or anaphylactic reaction which is quite rare.
Who are not eligible for Covid-19 vaccination?
1. Children below 16 years of age as of now. This is due to the fact that very few children have been part of clinical trials of vaccine. Hence, there is less evidence and data regarding the efficacy and dose of covid-19 vaccine among children.
2. People with severe allergic or anaphylactic reactions due to vaccine.
3. Women who are pregnant are advised not to take vaccines until further investigations are done. However, till now, no contraindications have been reported. Pregnant women who are frontline health workers or are clinically vulnerable to covid-19 infections can take vaccines.
4. People suffering from Covid-19 infections. If you are actively suffering from covid-19 infection or just recovered, experts recommend waiting until you have fully recovered. Later, you can take the vaccine.
Which are the different types of covid-19 vaccines that are manufactured?
Since the pandemic had begun, the whole world started to manufacture vaccines. Different types of antigens are used to create covid-19 vaccines all around the world. However, there are 4 prominent types of vaccines that are manufactured.
- 1. Protein subunit
- 2. Viral vector
- 3. Whole virus
- 4. RNA
Protein Subunit
Subunit vaccines are vaccines that contain specific parts (subunits) of vaccine and not the whole virus. The subunits are protein in nature. These subunits are recognized by our immune system and get lead to a specific immune response.
These are created by inserting specific genetic code of virus into yeast or bacterial cell. This cell translates the genetic code into proteins which are then extracted, purified and used as active ingredient in cell.
Vaccines of Novavax are of this kind.
Viral Vector
This type of vaccine uses a safe virus- a virus that is unable to produce disease. This virus is encoded with genetic code that produces the proteins similar to proteins of Covid-19 such as ‘Spike’ protein.
These proteins are recognized by immune system and produce an immune response. Thus, the virus acts as a carrier or a vector for antigenic proteins.
The first viral vector vaccine to be approved for vaccination is Oxford-AstraZeneca Vaccine.
Whole virus
This vaccine uses the whole virus instead of its subunits. They are of 2 types:
Inactivated
This type of virus are either killed or altered in a sense that they cannot replicate. As they do not contain any live viruses, they cannot cause diseases. However, their efficacy could be lesser than live attenuated viruses.
Live attenuated
These are live viruses that can provide normal immune response in body. However, they are severely weakened and hence not able to produce diseases inside body. This vaccine has more efficacy than inactivated ones. These are not used much in immunocompromised people as they might replicate due to unopposed immune response and cause disease.
Vaccine of Bharat Biotech – COVAXIN uses inactivated viruses.
RNA
RNA vaccines use mRNA (messenger RNA) as an active ingredient. This mRNA is genetically engineered to code for proteins such as ‘Spike’ proteins of covid-19 that can lead to immune response. The mRNA is surrounded by a layer of lipid membrane. This membrane allows easy entering into body and also easy diffusion into cell. Once the mRNA is inside the cell, it is translated in desired antigenic proteins which are recognized by immune system. Therefore, this produces an immune response.
Pfizer-BioNTech and the Moderna Covid-19 vaccines are both RNA vaccines.
Thank you so much, this article was very informative and helpful.
Your welcome!