Comparative Systematic Review and Efficacy of Various Vaccines Against SARS-COV-2

Deepak Bharati¹, Maria Alva¹, Simona D’souza¹, Sanya Lisboa¹, Sohail Sayyed¹

Introduction to COVID-19

A new terror to this world has been named Coronavirus.

th From the beginning of the 20 century, these viruses have been seen. The Chicken was the first infected with virus which caused the respiratory ailments [1]. The array of hosts they infect and their types escalated over decades, each of which is linked to the emergence of respiratory diseases of unique pathological differences.

The main cause of the disease is the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) [2].

The disease trespasses from one individual to another by means of the respiratory route. The transmission of the disease is possible when an infected person coughs, sneezes, talks, or breathes within a range of 1.8 meters. New infection can develop when particles containing the virus are exhaled from an infected person and gets into the mouth, nose, or eyes of a non-infected person [3]. Human-to-human interaction is the most common way for SARS CoV2 virions to initiate a new infection.

Coronavirus disease 2019 (COVID-19) is said to be more infectious than influenza but less as compared to measles. It frequently proliferates in clusters, wherein infections may be traced returned to an index case or geographical location [4]. The infection can be transmitted from an infected person to others up to two days before they show symptoms. It is also possible that the infection is carried even if the patient is asymptomatic [5]. Moderate instances of the contamination convey the virus for 7-12 days and weeks or greater for excessive instances. The diploma to which the virus is infectious is uncertain, however, studies have indicated that the pharynx reaches the top viral load about 4 days after the contamination or the primary week of symptoms, and declines later.

Respiratory failure from Acute Respiratory Distress Syndrome (ARDS) is the main reason for deaths in the COVID-19 patients [6]. 39% of the overall pooled mortality rate is seen in COVID-19 patients due to ARDS. Respiratory failure includes various risk factors such as

older age, male sex, cardiovascular diseases, laboratory markers, and high viral load on admission.

Polymerase chain reaction testing is currently used for the diagnosis of COVID-19. However, because of falsenegative test results, presumptive tests such as nasal swabs, clinical, laboratory and imaging findings are used to detect SARS-CoV2.

By using preventive measures, the spread of the virus can be controlled. These measures include staying at home, wearing a mask, washing hands for about 20 seconds, avoiding crowded places, avoid touching eyes, mouth and nose, maintaining respiratory hygiene [7].

associated with cell recognition and the fusion of viral and cellular membranes respectively. The E protein plays an important role in membrane penetration in the host cell, virus-cell interaction, and the assembly of the virions.

The binding of the S protein takes place on the surface of the human cells, mainly present in the lungs via the Angiotensin Converting Enzyme 2 (ACE2) receptor [10]. The S protein is also broken down by the host cells through enzymes such as trypsin and furin. Hence, activation of the membrane fusion mechanism is triggered. Once the virus enters the cytoplasm through endocytosis, it proceeds with a three-step reaction for membrane fusion, involving receptor-binding and induced conformational changes in the S protein

Immunity to COVID- 19

Immunity development to SARS-CoV2 is yet to be understood fully, but research suggests that there is a response seen through both antibody-mediated as well as cell-mediated.

Antibody-mediated immunity: Also known as humoral immunity includes immunity through helper T cells, B cells which differentiate into plasma B cells which act as an antibody to the antigen. As per research, it says that after the infection has been developed, IgM and IgG are detected in the body. IgM antibodies are at their peak at the initial stage of the infection and remain in the body for approximately 20 days and then decline gradually. Whereas IgG is to be seen at the later stage, mostly after 25 days from the onset of the infection and remains up to 120 days. Neutralizing antibodies are also found in adults which remain in the body for several months. The Maternal IgG antibodies are seen to be transferred to the child through the placenta and remain for about 8 months after infection.

Cell-mediated immunity: Immune system, which does not require any involvement of antibodies but is activated through phagocytes, antigen-specific cytotoxic T- cells, and through the release of different cytokines due to the presence of antigens is known as cell-mediated immunity. People generally develop a strong and broad T-cell response, including both CD4+ and CD8+ T-cells, and also have a memory phenotype. These cells having a halflife of about 3-5 months in recovered patients and up to 8 months after primary infection.

Vaccines

Introduction to Vaccines

The world is facing a global pandemic wherein so many people have lost their lives and many are battling against this deadly disease. COVID-19 has very serious and lifethreatening effects as it spreads at such a high rate. Vaccines are required to put an end to this pandemic. Although wearing a mask, maintaining social distancing, and following all the social norms may reduce the chance of getting the virus, but that is not sufficient. It is necessary to build our immune system to help us fight against this virus, and this can be done with the help of vaccines. Many companies have been successful in doing so, and vaccines are now available to people across the globe. By getting vaccinated, the chain of the virus can be broken, and the virus won‟t get a host to survive, at least till herd immunity is achieved. Vaccines will help reduce cases of hospitalization and death, which is of major concern.

A biological preparation given to a person provides that person immunity against a particular infectious disease is known as a vaccine [11]. A vaccine can be differentiated as prophylactic or therapeutic. The disease-causing unit, such as the toxin, sugar, protein, or the virus, is weakened These components therefore, trigger an immune response and help to induce antibodies that are memorized and can decrease the effect and severity of the diseases.

Vaccination can be a very important and primary way to arrest the widespread control of any infectious disease and provide the gift of life [12]. For example, Vaccines for polio, measles, tetanus, whooping cough, etc. have saved the lives of millions.

Once a sufficient number of people are vaccinated, the chances for an outbreak of a particular disease become so low that even the ones who aren‟t vaccinated benefit. Eventually, a bacteria or virus simply will not have enough eligible hosts to feed on and will subsequently die out. This concept is known as “herd immunity” wherein every single individual may necessarily not be vaccinated and has helped to eradicate the disease [13].

Serious diseases can spread rapidly and can cause concern in pregnant women along with the fetus. But with the help of vaccines, we can make sure that the immunity developed will keep the mother and the baby safe. MMR vaccines have been advised on women who are expecting to conceive so that they can be away from diseases such as mumps, measles and rubella. It is likewise encouraged that pregnant ladies must take a shot of influenza and whooping cough vaccine as it guarantees immunity for each mother and fetus and effects in lesser possibilities of having the virus [14].

Monovalent vaccines are those which are effective against only one microorganism, whereas polyvalent vaccines are used to provide immunity against more than one microorganism.

Types of COVID-19 Vaccines [15] Four major types of vaccine used are, depicted in figure 2.

1) Whole virus 2) Protein subunit 3) Viral vector 4) Nucleic acid (RNA and DNA)

1. Whole Virus Vaccine [16]

The whole virus vaccine is further subdivided into:

a) Live attenuated vaccine: Live attenuated vaccine virus which is disabled such that it does not carry the efficiency to cause the disease, but it can alarm the immune system [17].

Advantage 1) Well-known technology.

2) Strong immune response acquired.

3) Easy to manufacture.

Disadvantage 1) Relatively sensitive to temperature, so special attention should be given to storage.

2) Not be given to people with compromised immune 3) Might trigger disease, but very rare case b) Inactivated vaccine: Virus used in an inactivated type of vaccine undergoes physical and chemical treatment which destroys the genetic material of the virus. They cannot infect cells and replicate but can boost immune response. They are safe to use, but low response compared to live attenuated vaccines.

Advantage 1) Given to people with compromised immune systems. 2) Since no live component is present, there is no risk of the vaccine triggering the disease.

3) Relatively stable.

Disadvantage 1) Requirement of Booster shots for proper immunity against disease Four inactivated vaccines Sinopharm BIBP COVID-19 vaccine also known as BBIBP-CorV, developed by Sinopharm's Beijing Institute of Biological Products, CoronaVac, also known as the Sinovac COVID-19 vaccine, is an inactivated virus COVID-19 vaccine developed by the Chinese company Sinovac Biotech., Covaxin India's First Indigenous COVID-19 Vaccine. Devlped by Bharat Biotech is developed in collaboration with the Indian Council of Medical Research (ICMR) - National Institute of Virology.

2. Protein Subunit

A protein is extracted from the virus which could be alive or inactivated, purified, and injected as a vaccine for the disease. For the coronavirus, most commonly, the spike protein is used. Virus-like substances work in the same manner and are safe for use as they do not contain any disease-producing components. But it requires the addition of few a chemical in order to boost immunogenicity [18].

Two protein subunit vaccines (EpiVacCorona is a COVID-19 preventive vaccine developed by the Vektor State Research Center of Virology and Biotechnology in Russia.) Advantage 1) Noninfectious vaccine.

2) Protein subunit has a strong humoral response.

3) Strong innate Immune Response Disadvantage 1) High risk of infection and inflammation which may result in adverse reactions.

2) Used for production of multivalent vaccine formulation.

3. Viral Vector

The gene for a pathogen protein is inserted into a different virus that can infect without causing the disease. The safe viruses are used as a transporter of the protein component which will trigger the immune response. Some reproduce in the body, but some do not reproduce. Three viral vector vaccines (Sputnik Vis an adenovirus viral vector vaccine from COVID-19 developed by Gamaleya Reearc Institute of Epidemiology and Microbiology in Russia., Oxford-AstraZeneca, sold under brand name Covishield and Vaxzevria is a viral vector for prevention of Covid-19 devloped by Oxford University & AstraZeneca, Convidecia, is a single-dose viral vector vaccine for COVID-19 developed by CanSino Biologics [19].

Advantage 1) Provide long-term gene expression.

2) Dividing and non-dividing cells can be infected.

3) Much safer vaccine.

4) Produce high immunogenicity.

Disadvantage 1) Pre-existing immunity is one of the major drawbacks. 2) Generation of the competent-replication virus may result in tumorigenesis.

4. Nucleic Acid

This type of vaccine promotes nucleic acid for coding as an antigen instead of a protein antigen or a virus expressing the protein [20].

DNA plasmid enters the nucleus and is translated to mRNA for the expression of a protein. Directly mRNA can also be injected which requires no translation, but is less stable than DNA type. Two RNA vaccines (PfizerBioNTech, is a COVID-19 vaccine sold under the brand name Comirnaty, is an mRNA-based COVID-19 vaccine developed by the German, Moderna COVID-19 vaccine, codenamed mRNA-1273 and sold under the brand name Spikevax, is a vaccine developed by Moderna,).

Working of vaccines

A healthy immune machine facilitates maintaining invaders far away from us. The immune system comprises of various types of cells. Harmful pathogens are defended and removed from the body because of these cells. The important thing is that the immune system recognizes the harmful substance. Vaccines aim to teach the body to recognize new diseases. Upon recognition, it stimulates the body to produce antibodies against the antigens of pathogenic diseases. It also primes immune cell response to the disease in the future. There are various methods by which the vaccines work and act as an antigen, and are as follows:

1) Sugar or protein is used to make the pathogen.

2) The virus, which is either inactivated or is dead, is used.

3) The toxic parts of the virus are made into toxoids. 4) The virus is weakened via the way of physical or chemical remedy.

Table 1. Calculation for the efficacy of Pfizer Vaccines No infection with

% of the vaccinated group that developed COVID-19= 8/22,000= 0.036% % of placebo group that developed COVID-19= 162/22,000= 0.74% Injectables are the preferred route for the administration of vaccines. They are made up of two units. The antigen is the first component which includes a part of the disease which is used to warn the body about a harmful substance. Adjuvant is the second component that helps in triggering a strong immune response [20].

Different Vaccines in the Market Calculation for the efficacy of Vaccines

The efficacy rate of vaccines is calculated through clinical trials where the vaccine is tested on a large number of people. These individuals are divided into two categories. One gets the vaccine, and the other gets a placebo. The placebo is a substance that is identical to the treatment being tested in the clinical trial but does not contain the active ingredient. Once they receive the particular treatment i.e., vaccine or the placebo the participants of the trial are allowed to live their lives while the scientists monitor whether or not the

PFIZER

(n= total no. Of people under the trial) (n=44,000) [22, 23].

Pfizer No. of people under the trial

Relative risk of getting COVID-19= 0.036/0.74= 0.049 Vaccine Efficacy= 1-0.049= 95.1%.

participants get infected by Covid-19. The general range of members inflamed through the sickness is noted. For example, if 40,000 participants took part in the clinical trial, from which about 200 participants were infected by the disease, these 200 participants are divided based on which group they belong to i.e., whether they belong to the vaccine group or the placebo group.

 If the participants infected in each group are equal, then the efficacy of the vaccine is said to be 0%  If all the 200 were in the placebo group and zero people got the disease, then the vaccine would have efficacy of 100%  If 190 participants belonged to the placebo group and 10 belonged to the vaccine group, then the vaccine would be 95% effective.

The above case means that each vaccinated person is 95% less likely to get the disease than a person without a vaccine each time they are exposed to Covid-19 [28].

.

COVID-19 Infected with COVID-19

8 162 170

Table 2. Calculation for the efficacy of Moderna Vaccines. No infection with COVID-19

% of the vaccinated group that developed COVID-19 = 11/15,000 = 0.073% % of placebo group that developed COVID-19 = 185/15,000 = 1.233%

Table 3. Calculation for the efficacy of Johnson & Johnson Vaccines.

% of the vaccinated group that developed COVID-19 = 116/19,514 = 0.594% % of placebo group that developed COVID-19 = 348/19,544 = 1.78%

Table 4. Calculation for the efficacy of Sputnik V Vaccines.

No infection with COVID % of the vaccinated group that developed COVID-19 = 16/17,032 = 0.093% % of placebo group that developed COVID-19 = 62/5,682 =1.091% (According to the first interim analysis in March 2021)

Table 5. Calculation for the efficacy of Covaxin Vaccines. No infection with COVID

% of the vaccinated group that developed COVID-19 = 7/12,900 = 0.054% % of placebo group that developed COVID-19 = 36/12,900 = 0.279%

MODERNA

(n=30,000) [23].

Moderna No. of people under the trial

Relative risk of getting COVID-19 = 0.073/1.233 = 0.059 Vaccine Efficacy = 1-0.059 = 94.1%.

JOHNSON & JOHNSON

(n=40,000 but data collected from 39,321 participants) [24].

No. of people in the No

Johnson & Johnson

trial COVID Relative risk of getting COVID-19 = 0.594/1.78 = 0.333 Vaccine Efficacy=1-0.333 = 66.7%.

SPUTNIK V

(n=22,714) (Placebo: Vaccine=1;3) [25].

Sputnik No. of people in the trial Relative risk of getting COVID-19 = 0.093/1.091 = 0.085 Vaccine Efficacy =1-0.085 = 91.5%.

COVAXIN

(n=25,800) [26].

Covaxin No. of people under the trial

Relative risk of getting COVID-19 = 0.054/0.279 = 0.1935 Vaccine Efficacy =1-0.193 = 80.6%

Infected with COVID-19

11 185 196

infection with Infected with COVID-

-19 19 116 348 196 -19 Infected with COVID-19 16 62 78

-19 Infected with COVID-19

7 36 43

Table 6. Calculation for the efficacy of Novavax Vaccines. No infection with COVID

% of the vaccinated group that developed COVID-19 = 6/7,500 = 0.08% % of placebo group that developed COVID-19 = 56/7,500 = 0.746%

ds DNA encoding for the Spike protein is protected in a safe virus. The infected cell expresses the Spike protein which At least one study finds it has little effect Injection site tenderness, injection site Hypersensitivity to the active substance hydrochloride

NOVAVAX

(n=about 15,000) [27].

Novavax No. of people under the trial

Relative risk of getting COVID-19 = 0.08/0.746 = 0.1072 Vaccine Efficacy =1-0.1072 = 89.3%.

Comparison of different marketed COVID-19 vaccines

Primary Developers Oxford University, AstraZeneca Each Dose 5*10^10 particle/dose Dosing 2 doses-8 to 12 weeks apart Shelf life 6 months Mode of Intramuscular Injectable 0 Storage 2-8 C 18 years and above Targeted population Working leads to an immune response [32] against the South African variant Variants appears effective against the UK Brazilian variants.

pain, headache, fatigue, myalgia, malaise, pyrexia, chills, arthralgia, .[49] nausea, redness, itching or any of the excipients such Histidine, L-Histidine Contraindications monohydrate, Magnesium chloride hexahydrate, Polysorbate 80, Ethanol, Sucrose, Sodium chloride, Disodium edetate dihydrate, Water for injection.

Price $3-$4 per dose Country of origin U. K.

-19 Infected with COVID-19

6 56 62 Bharat Biotech, ICMR 2 doses-4 to 6 weeks apart 6 months 78% 0 2-8 C 18 years and above SARS-CoV2 is chemically inactivated (with a chemical called beta-propiolactone) so it cannot replicate but all the proteins remain intact [32]. .

Show significant immunogenicity against the but rapidly emerging variants.

and Injection site pain, headache, fatigue, fever, body ache, abdominal pain, nausea, vomiting, dizziness-giddiness, tremor, sweating, cold, cough, injection site swelling People having a history of allergies, have a as L- fever, have a bleeding disorder or are on a blood thinner, are immune-compromised or are on a medicine that affects the immune system, are pregnant, are breastfeeding, have received another COVID-19 vaccine, any other serious health-related issue [33].

$4.2 per dose India

mRNA encoding for the Spike protein is expresses the Spike protein resulting in against the UK variant as well as the chills, joint pain, fever, swelling at the anaphylaxis) after a previous dose of an 19 vaccine or any of its reaction of any severity to a previous

Type of Vaccine Encapsulated mRNA Vaccine Primary Developers Pfizer, BioNTech, Fosun Pharma [36] Each Dose 30 mcg/dose Dosing 2 doses-21 days apart Shelf life 6 months Mode of Efficacy 95% 0 Storage -80 C Targeted population 12 years and older protected in lipid-nanoparticles Working bubbles). Once absorbed, an immune response [32].

Lab data suggest, “quite Variants South African and Latin variants.

Pain, fatigue, headache, muscle [34,35] injection site, nausea, malaise.

Severe allergic reaction mRNA COVID- components. An immediate Contraindications dose of an mRNA COVID-19 vaccine or any of its components. (including polyethylene glycol) [50].

Price $19.50 per dose Country of origin Multinational Encapsulated mRNA Vaccine Moderna, BARDA, NIAID [36] 6 months 94.10% 0 2-8 C for 30 days 18 years and older mRNA encoding for the Spike protein is (like soap protected in lipid-nanoparticles (like soap the cell bubbles). Once absorbed, the cells express the Spike protein resulting in an immune response [32].

effective” Lab data suggest, “quite effective” against the UK variant as well as the South African and American Latin American variants.

pain, Pain, swelling, tiredness, chills, fever, swelling of lymph nodes, headache, muscle, and joint [49] pain, nausea, vomiting.

(e.g., Should not be administered to individuals with a known history of a severe allergic reaction. allergic (e.g., an anaphylactic reaction occur following administration of the Moderna COVID-19 Vaccine [39].

$25-$37 per dose U.S.

spike proteins. Additional element called Effective against UK and South African Injection site pain, rash, headache, muscle pain, fever, nausea, vomiting, tenderness

in refrigerator to a carrier protein and adsorbed adjuvant. It forms immunity due effective against variants.

Nanoparticles are coated with Working an adjuvant is added which boosting the immune reaction [32] Variants [49].

Contraindications Information, not available Price $16 in the US Country of origin U.S.

Type of Viral Vector Vaccine Protein Subunit Vaccine Gamaleya Research Federal Budgetary Primary Institute, Acellena Institution, Developers Contract Drug Research, Center of and Development Biotechnology (1.0 ± 0.5) × 10^11 Each Dose particles/dose Dosing 2 doses-21 days apart 2 doses-21-28 days apart Shelf life 2 years 2 years Mode of Store in a dark place at a Storage temperature not Stable exceeding -18℃ Targeted 18 years and older 18-60 years population Vaccine relies ds DNA encoding for synthesized the Spike protein is SRS-CoV-2 proteins, conjugated protected in a safe virus.

Working The infected cell on aluminum expresses the Spike protein which leads to an to artificially immune response [32].

peptides Unknown. Clinical trial data was largely Russian scientists Variants conducted in Russia before the emergence of major variants.

synthetic ds DNA encoding for the Spike protein is protected in a safe virus. The infected cell allows expresses the Spike protein which leads to . an immune response [32].

Based on clinical studies in Africa, UK, and Latin America, there is evidence the vaccine is effective against the variants, although less so against the South African and Latin American strains.

Injection site pain, rash, headaches, muscles soreness, fever, fatigue, nausea, redness, swelling, tiredness, chills [49].

Known history of a severe allergic reaction (e.g., anaphylaxis) to any component of the .[50] vaccine $10 per dose The Netherlands, U.S.

Inactivated Virus based Vaccine Research State Research Chumakov Centre Virology and 2-8℃ 18-60 years on chemically The vaccine includes spike protein peptide antigen of on the outside of the viral envelope and genetic material on the inside.

The virus has been so that its -containing genetic material cannot infect cells or replicate but can still trigger an synthesized immune response.

Russian researchers say that say it is because it is based on the whole virus, it will be effective against most variants or mutations.

Fever or chills, cough, shortness of breath, fatigue, muscle pain, headache, loss of taste or smell, throat, stuffy nose, nausea,

China National Pharmaceutical Group CoV2 is chemically inactivated (with propiolactone) so it all the proteins remain African variant but the effect is weaker as lactating women, cancer patients currently Flu-like symptoms, chills, fever, arthralgia, myalgia, asthenia, soarheadache vomiting, diarrhea Hypersensitivity, pregnancy and period of breastfeeding, acute Contraindicatio infectious and nonns infectious diseases, exacerbation of chronic diseases Free in Russia and US Price $10 in the international market per dose Country of Russia Russia origin Type of Vaccine Inactivated Virus Vaccine Beijing Institute of Biological Primary Developers Each Dose 2 mcg/dose Dosing 2 doses-21 days apart Efficacy 79% Storage 2-8℃ Targeted population 18-60 years SARS- a chemical called betaWorking cannot replicate but intact [32].

Triggers immune response Variants compared to the original variant.

Headache, fever, muscle and nausea, diarrhea, itchy Uncommon-loss of appetite, hypersensitivity. Rare-allergic drowsiness, nasal congestion, acne, ear discomfort. Very tonsillitis, gastritis, blurry mouth ulcers Severe allergic reactions, Contraindications on chemotherapy Price <$145 for 2 doses Country of origin China No severe side effects Severe allergic reactions, pregnancy, and breastfeeding.

Russia Inactivated Virus Vaccine Products; Sinovac 3 years 50% 2-8℃ 18-59 years SARS-CoV2 is chemically inactivated (with a chemical called betapropiolactone) so it cannot replicate but all the proteins remain intact [32].

against South Unknown, although a study in Brazil demonstrated 50.4% efficacy at preventing symptomatic infections.

joint pain, skin, cough.

constipation, reaction, Increase in blood pressure, pain at the limb pain, injection site, rashes, nausea, headache rare-tremors, vision, asthma, pregnant and Severe allergic reactions.

$60 per dose China

defense adenovirus type 5 as the vector to Each Dose Information not found Dosing 1 dose Storage 2-8℃ Targeted population 18 years and older The vaccine is a genetically vaccine candidate with the Working express SARS-CoV-2 spike protein.

Variants Information not found Side Effects Pain at the injection site, fever Contraindications Information not found Price Information not found Country of origin China

Conclusion

The article aims to get an understanding of the different vaccines available and also to get a fair idea about the similarities and differences among these vaccines. These vaccines could be categorized based on various factors such as their type or based on how they work, their route of administration, the number of doses given for a particular vaccine, the age group as to who are eligible to get the vaccine, their storage conditions, etc.

Based on the Type of Vaccine discussed earlier there are the Viral Vector type, Inactivated Virus Vaccine, the mRNA Vaccine and the Protein Subunit Vaccine. The Vaccines are further subcategorized in the following manner.

3 doses over a period of 2 months 18 years and older The vaccine targets the receptor-binding domain (RBD) of the SARS-CoV-2 S engineered protein which is responsible for the replicationengagement of its cellular receptor, ACE2 and is an attractive vaccine target to induce immune responses focusing on blocking receptor binding.

Showed neutralizing activity against the South African variants although with weaker activity than against the original virus.

Redness, swelling China Based on the number of doses, these vaccines are given as a single dose, two doses, and even three doses. The vaccines are further categorized as follows.

Based on age group, vaccines are given to the people. These vaccines are not given to children under a certain age group. This is because the trials conducted did not include children and hence no data has been established as to its effect on children. Vaccines are further categorized as follows.

Based on age group, vaccines are given to the people. These vaccines are not given to children under a certain age group. This is because the trials conducted did not include children and hence no data has been established as to its effect on children. Vaccines are further categorized as follows.

18 years Novavax, Janssen, Sputnik V, and older EpiVacCorona, CoviVac, Sino pharm, Sinovac, CanSinoBio, RBD-Dimer Based on storage conditions, most of these vaccines can be stored at normal refrigerator conditions whereas there are a few vaccines that need deep-freeze conditions. As per these conditions' vaccines are further categorized as follows.

Based on the route of administration, all these vaccines are Intramuscular Injections which are given in the deltoid muscle.

Hence, in this way, the similarities and differences between these vaccines can be understood.

March 2021, it's been 15 months since the first case of COVID-19 was reported in Wuhan, China, and now we have twelve or more authorized vaccines which are available to people across the globe. Covaxin, AstraZeneca (Covishield), Pfizer, Moderna, Sputnik V, Novavax, Johnson & Johnson, Sinovac, Sino pharm, CanSinoBio, CoviVac, EpiVacCorona, and still many more to come which are under clinical trials.

Although it would not be lawful to compare vaccines based on their efficacy rates but still looking at the efficacy numbers, it is often assumed that Pfizer and Moderna are better in efficacy as compared to the rest of the vaccines, but this is not the case as the trials of each is done in very different circumstances. Trials of each vaccine were done in different seasons, different epidemiological seasons, different countries, different clinical trials, and most importantly with different strains of the virus. For example, trials for Pfizer and Moderna were executed within the U.S. during the summer whereas Johnson & Johnson held their U.S. trials when there were more opportunities for participants to be exposed to infection, moreover, most of the trials took place in countries such as South Africa and Brazil where not only their case rates were high but also the virus there was different (variants). These variants have a higher chance of getting the participants infected. Even though the trials were taken in such situations, the vaccine showed a significant reduction of the infection. If the Pfizer and Moderna vaccines were tested under such conditions it is possible that their efficacy numbers would be different.

Dr. Adalja an adjunct assistant professor at the Johns Hopkins Bloomberg School of Public Health, attached to the John Hopkins Center for Global Health and is emergency medicine, critical care, and infectious disease specialist in Pittsburgh says that „the goal of a vaccine program for COVID-19 is not necessarily to get to COVID zero but to tame this virus, defang it and the most important thing about COVID-19 vaccines is that they remove the ability of the virus to cause serious hospitalization or death.‟ All of these vaccines are effective and safe. The important thing about all these vaccines is that they will protect us from hospitalization and death and this will help us end the pandemic. The answer to the question 'Which vaccine is the best?' is 'The one which is offered to you.

Conflict of Interest

There is no conflict of interest in research for the literature, writing and documenting this review article.

Authors Contribution

Ms. Simona D‟Souza, Ms. Maria Alva have contributed in collecting the relevant data for this review, Ms. Sanya Lisboa and Mr. Tanmay Golekar have contributed for the doing the literature survey and Mr. Sohail Sayyed has contributed in editing the manuscript as per authors instruction and Dr. Deepak Bharati has done proof reading of the manuscript.

Authors Funding

Authors have not received any funds/grants from any funding agency to conduct this review.

Acknowledgement

Authors are thankful to Chairman, Aldel Education Trust and Principal, St John Institute of Pharmacy and Research for their motivation and support.

References

References

1. Coronavirus disease 2019 (COVID-19) - Prognosis | BMJ Best Practice US.
2. Pathophysiology, Transmission, Diagnosis, and Treatment of Coronavirus Disease 2019 (COVID-19): A Review | Critical Care Medicine | JAMA | JAMA Network.
3. Genomic epidemiology of superspreading events in Austria reveals mutational dynamics and transmission properties of SARS-CoV-2 | Science Translational Medicine (sciencemag.org).
4. Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study - The Lancet Infectious Diseases.
5. Harrison AG, Lin T, Wang P. Mechanisms of SARS-CoV-2 transmission and pathogenesis. Trends in immunology. 2020 Oct 14.
6. Lalchhandama K. The chronicles of coronaviruses: the bronchitis, the hepatitis and the common cold. Science Vision. 2020; 1:43-53.
7. https://en.wikipedia.org/wiki/COVID-19.
8. https://en.wikipedia.org/wiki/File:Fphar-11-00937-g001.jpg.
9. Verdecchia P, Cavallini C, Spanevello A, Angeli F. The pivotal link between ACE2 deficiency and SARS-CoV-2 infection. European journal of internal medicine. 2020; 76:14-
11. www.who.int.Coronavirus disease (COVID-19): How is it transmitted? Available from: https://www.who.int/newsroom/q-a-detail/coronavirus-disease-covid-19-how-is-ittransmitted.
12. www.who.int. How do vaccines work? Available from: https://www.who.int/news-room/feature-stories/detail/how-dovaccines-work.
13. World Health Organization. WHO position on HPV vaccines. Vaccine. 2009; 27(52):7236-7.
14. Healthline.com. Everything You Need to Know About Vaccinations. Available from: https://www.healthline.com/health/vaccinations
15. Wikipedia.org.Vaccine. Available from: https://en.wikipedia.org/wiki/Vaccine.
16. Wikipedia.org. COVID-19_vaccine. Available from:.https://en.m.wikipedia.org/wiki/COVID-19_vaccine.
17. www.gavi.org. What are whole virus vaccines and how could they be used against COVID-19? Available from: https://www.gavi.org/vaccineswork/what-are-whole-virusvaccines-and-how-could-they-be-used-against-covid-19.
18. www.gavi.org. What are whole virus vaccines and how could they be used against COVID-19? Available from: https://www.gavi.org/vaccineswork/what-are-whole-virusvaccines-and-how-could-they-be-used-against-covid-19.
19. cglife.com.mrnna-vaccines-what-you-need-to-know. Available from:https://cglife.com/blog/mrna-vaccines-what-you-need-toknow/
20. theconversation.com. From adenoviruses to RNA: the pros and cons of different COVID vaccine technologies Available from: https://theconversation.com/from-adenoviruses-to-rna-thepros-and-cons-of-different-covid-vaccine-technologies
21. https://www.google.com/amp/s/www.researchgate.net/figure/ Advantages-and-disadvantages-of-major-viralvectors_tbl1_281623861/amp
22. https://www.researchgate.net/figure/Advantages-anddisadvantages-of-different-vaccine-platforms-for-parasiticdiseases_tbl1_335954958
23. https://youtu.be/huFLxbBw9OM
24. towardsdatascience.com. pfizer and moderna vaccine efficacy calculated from data. Available form: https://towardsdatascience.com/pfizer-and-moderna-vaccineefficacy-calculated-from-data-9566897173c
25. https://youtu.be/R0wn_vIfNKQ
26. sputnikvaccine.com. The sputnik v vaccine‟s efficacy is confirmed at 91.4% based on data analysis of the final control point of clinical trials. Available from:https://sputnikvaccine.com/newsroom/pressreleases/thesputnik-v-vaccine-s-efficacy-is-confirmed-at-91-4-based-ondata-analysis-of-the-final-control-po/
27. www.news18. bharat-biotechs covaxin has 81% efficacy heres how it compares to serum institutes covishield com . Available from https://www.news18.com/amp/news/india/bharatbiotechs-covaxin-has-81-efficacy-heres-how-it-compares-toserum-institutes-covishield-3496130.html
28. https://www.novavax.com/sites/default/files/202011/2019nCo V302Phase3UKVersion2FinalCleanRedacted.pdf
29. https://youtu.be/K3odScka55A
30. www.raps.org. covid 19vaccine tracker. Available from. https://www.raps.org/news-and-articles/newsarticles/2020/3/covid-19-vaccine-tracker
31. nytimes.com. covid 19vaccine tracker . Available from: .https://www.nytimes.com/interactive/2020/science/coronaviru s-vaccine-tracker.html
32. www.seruminstitute.com. Available from:.https://www.seruminstitute.com/pdf/covishield_fact_she et.pdf
33. https://www.facebook.com/lapipette.labs/?ref=py_c
34. www.bharatbiotech.com.Available from: https://www.bharatbiotech.com/images/covaxin/covaxin-factsheet.pdf
35. www.cdc.gov.Availbale from:https://www.cdc.gov/coronavirus/2019- ncov/vaccines/different-vaccines/Pfizer-BioNTech.html
36. www.fda.gov.emergency preparedness and response coronavirus disease. .Available from: https://www.fda.gov/emergency-preparedness-andresponse/coronavirus-disease-2019-covid-19/pfizer-biontechcovid-19-vaccine
37. www.cdc.gov.Availabe from:https://www.cdc.gov/vaccines/covid-19/info-byproduct/clinical-considerations.html
38. www.cdc.gov. Available from:https://www.cdc.gov/coronavirus/2019- ncov/vaccines/different-vaccines/Moderna.html
39. www.ema.europa.eu. Available from: https://www.ema.europa.eu/en/documents/productinformation/covid-19-vaccine-moderna-epar-productinformation_en.pdf
40. www.cdc.gov.Available from:https://www.cdc.gov/vaccines/covid-19/info-byproduct/moderna/index.html
41. wikipedia.org. Available from:https://en.wikipedia.org/wiki/EpiVacCorona
42. www.precisionvaccinations.Avaible from:https://www.precisionvaccinations.com/vaccines/epivacc orona-vaccine
43. www.precisionvaccinations.com. Available from:https://www.precisionvaccinations.com/vaccines/covivac -russia-covid-19-vaccine
44. wikipedia.org. Available from:https://en.wikipedia.org/wiki/CoviVac
45. www.bbc.com. Covid: What do we know about China's coronavirus vaccines?. Available from. https://www.bbc.com/news/world-asia-china-55212787
46. wikipedia.org. Available from. https://en.wikipedia.org/wiki/BBIBP-CorV
47. wikipedia.org. Available from: https://en.wikipedia.org/wiki/CanSino_Biologics
48. wikipedia.org.Availabe from:https://en.wikipedia.org/wiki/ZF2001
49. www.precisionvaccinations.com. Available from:https://www.precisionvaccinations.com/vaccines/zf2001- covid-19-vaccine
50. www.yalemedicine.org. Available from:https://www.yalemedicine.org/news/covid-19-vaccinecomparison
51. https://www.vizientinc.com/- /media/documents/sitecorepublishingdocuments/public/covid1 9_sidebyside_vaccinecompare.pdf.