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COVID-19 Vaccines

Published on Dec 22, 2020 and last reviewed on Jan 21, 2021   -  7 min read


A COVID-19 vaccine provides acquired immunity against the new Coronavirus. Read the article to know everything about the approved and undertrial vaccines.


Many pharmaceutical companies worldwide are working on potential vaccines for the new Coronavirus disease (COVID-19). With COVID-19 cases continuing to grow, scientists and doctors are working day and night to develop vaccines to slow the pandemic and lessen its damage.

How COVID-19 Vaccines Work?

Generally, when a virus or pathogen enters our bodies, they attack the cells and multiply. The body's immune system prevents this infection from progressing with the help of different types of white blood cells. Macrophages (one type of white blood cells) engulf and digest the virus and damaged cells. These macrophages leave behind some parts of the virus called antigens. B-lymphocytes, defensive white blood cells, produce antibodies that try to destroy the antigens left behind by macrophages. T-lymphocytes, another type of white blood cells, attack the infected cells in the body.

All these processes take a few days to weeks, and the immune system eventually fights the infection off (ideally). After the initial infection, the immune system remembers how to fight off that particular pathogen if it invades the body again. Some T-lymphocytes or memory cells remain in the body, and they attack immediately if the body reencounters the same virus.

COVID-19 vaccines are designed to provide the same immunity without getting infected with the virus. Different types of vaccines work in different ways, but in the end, all the vaccines lead to the formation of B and T-lymphocytes. These cells remember how to fight that virus in case the person gets infected in the future.

What Are the Types of COVID-19 Vaccines?

The four main types of COVID-19 vaccines are:

  1. Whole Virus Vaccines - Many vaccines use the entire virus, either in the live-attenuated form or inactivated form, to trigger an immune response. Live-attenuated vaccines use a weakened form of the virus, which cannot cause illness but can replicate. While viruses with a destroyed genetic material can no longer multiply, they can activate the immune system and are used in inactivated vaccines.

  2. Protein Subunit Vaccines - They contain viral protein, which triggers the immune system to make T-lymphocytes and antibodies. Only using the protein minimizes the risk of side effects, but the immune response might also be weak, which is why they often require adjuvants to boost the immune response.

  3. Nucleic Acid Vaccines - These vaccines either use viral spike protein or the viral RNA or DNA. When this genetic material enters the human cells, it uses our cells to make the viral antigen, which triggers an immune response. These vaccines are easier to make and are cheaper.

  4. Viral Vector Vaccines - These vaccines also give our cells instructions to produce viral antigens. But instead of using the nucleic acid from the virus, it uses a harmless virus (not the one against which the virus is targeted). Adenovirus (the virus that causes the common cold) is often used as a vector. The side effect of this vaccine is as many might already be exposed to various adenoviruses, and when it is used as a vector, the immunity destroys it, which results in an inadequate immune response.

COVID-19 Vaccine Timeline:

A COVID‑19 vaccine is intended to provide immunity or protection against the new Coronavirus (SARS-CoV-2). Before the current pandemic, as scientists were working on developing vaccines against SARS - Severe acute respiratory syndrome and MERS - Middle East respiratory syndrome, which are diseases caused by other strains of Coronaviruses, they already had an idea about the structure and function of this virus. This has accelerated the work that is being done for COVID‑19 vaccines. The work began on these vaccines in January, soon after the virus's genome was deciphered.

In November 2020, Moderna, BioNTech and Pfizer Inc, Gamaleya Institute, and the University of Oxford announced positive vaccine trial results. By December 2020, almost 40 vaccines were in Phase I to II of their clinical trials and 17 in Phase II to III. And by 19th December 2020, 16 countries had approved the BioNTech and Pfizer Inc vaccine (Tozinameran) for emergency use. United Arab Emirates (UAE) and Bahrain have authorized the vaccine manufactured by Sinopharm (China National Pharmaceutical Group Corp). By 16th December in the UK, around 1,38,000 people have received Tozinameran. The FDA (the United States Food and Drug Administration) granted an Emergency Use Authorization (EUA) for Tozinameran On 11th December 2020 and also granted a EUA for the Moderna vaccine (mRNA-1273) a week later.

Approved COVID-19 Vaccines:

1) Pfizer, BioNTech, and Fosun Pharma - The pharmaceutical company Pfizer, in collaboration with BioNTech (a German biotech company) and Fosun Pharma, developed a two-dose mRNA vaccine (Tozinameran or BNT162b2). After conducting trials on children and adults, on 9th November, the company's data showed that the vaccine was 90 % effective. The FDA then reported that the Pfizer vaccine, after the first dose, gave some protection, and almost full protection after the second dose on 8th December, and on 11th December, this vaccine was given the EUA by the FDA.

2) Moderna (National Institutes of Health) - It is a two-dose mRNA vaccine (mRNA-1273) that began testing in March. In August, the company's data showed a favorable immune response in 10 people between the ages of 56 and 70 and over the age of 70. In November, reports indicated the vaccine to be 94 % effective. And in mid-December, this vaccine was given EUA by the FDA.

3) Gamaleya Research Institute - It is a Russian institute, which developed a vaccine (Sputnik V or Gam-COVID-Vac) that has two components, a recombinant adenovirus type (rAd26) and type 5 (rAd5) vectors. In August, the vaccine received a "conditional registration certificate." The ongoing clinical trial in Russia involves 40,000 volunteers, and clinical trials have been announced in the UAE, India, Venezuela, and Belarus. The results of phase I and II trials found that the vaccine showed an immune response with mild side effects. The Sputnik V vaccine is 91.4 % efficient with mild side effects, and its vaccine efficacy against severe cases of Coronavirus is 100 %.

4) Sinovac Biotech - This is a Chinese company that developed an inactivated SARS-CoV-2 vaccine (CoronaVac). The phase III trials began in Brazil, Indonesia, and Turkey. The vaccine was granted emergency approval by the Chinese government for use on individuals at high risk of developing severe COVID-19 infection.

5) Wuhan Institute of Biological Products and Sinopharm - The vaccine BBIBP-CorV, an inactivated virus vaccine, is being tested by the Chinese company Sinopharm and developed by the Wuhan Institute of Biological Products. As the phase I clinical trial showed positive results, phase III trials began first in UAE and then in Morocco and Peru, which showed an efficacy of 86%. Bahrain and UAE have already approved the vaccine for use.

Ongoing COVID-19 Vaccine Projects:

1) Inovio - This pharmaceutical company designed the vaccine INO-4800, a nucleic-acid-based vaccine, in January 2020. Following authorization by the FDA, they started the human clinical trial in April 2020. After they got clearance from the FDA in November 2020, Phase II of the trial is ongoing.

2) Sanofi and GlaxoSmithKline (GSK) - These French and Britain pharmaceutical companies developed an adjuvanted protein vaccine. Initial results from a phase I/II clinical trial in December 2020 showed a poor immune response in older adults but sufficient immune response in adults between 18 and 49. The company is believed to launch the next phase of the trial in February 2021.

3) Sanofi and Translate Bio - The French drugmaker Sanofi is also working with Translate Bio, and they developed an mRNA vaccine in February 2020. Nonhuman trials conducted on monkeys and mice showed a strong immune response. The phase II trial results will be available soon, and the phase III study will start in early 2021. The vaccine is expected to be approved in the second half of 2021.

4) CanSino Biologics - China's CanSino Biologics Inc., backed by the Chinese military, is also developing a potential COVID-19 vaccine. They are using an adenovirus Ad5 to carry coronavirus proteins into the cells. The protein elicits an immune response when combined with another compound, called the adjuvant. This vaccine is called Ad5-nCoV or Convidecia. In July 2020, it was reported that the participants in the phase II trial showed a strong immune response to the vaccine. As older adults had a weaker response, two doses might be needed for them. The Chinese military approved the vaccine in June, and it was administered to the armed forces. As of December 2020, over 20,000 participants have enrolled for late-stage human trials in Pakistan, Saudi Arabia, and Russia.

5) Johnson & Johnson - In late July 2020, Johnson & Johnson began a phase I/II trial in humans after their adenovirus vaccine (Ad26.COV2.S) showed positive results in monkeys. In September 2020, a phase III trial with 60,000 participants began to test their one-dose vaccine. Due to unexplained illness in one of the participants, the trial was paused in October 2020. The study will resume in the US, and the company said that the vaccine would be ready for FDA approval by February 2021.

6) AstraZeneca and the University of Oxford - In April 2020, AstraZeneca and the University of Oxford announced the development of a recombinant adenovirus vaccine (AZD1222), which was based on a chimpanzee adenovirus that carries coronavirus proteins in the body. Phase III clinical trials began in Brazil, the US, and South Africa in August. When a volunteer developed transverse myelitis (a spinal inflammatory disorder), the study was halted in September 2020. A week later, the trials restarted in the UK and Brazil, and the FDA authorized the US trial to resume in October 2020. It was reported in November 2020 that the vaccine produced a strong immune response in a clinical trial involving participants over 70 years of age. But, the data released on 8th December 2020 showed that the vaccine was only 70 % effective.

7) Novavax - The SARS-CoV-2 recombinant spike protein nanoparticle with an adjuvant vaccine (NVX-CoV2373) developed by Novavax received massive funding from the Coalition for Epidemic Preparedness Innovations (CEPI). The virus proteins are attached to microscopic particles to form this vaccine. In August 2020, a phase II trial was launched in South Africa, and a phase III trial began in the UK a month later. In September 2020, a COVID-19 vaccine manufacturing agreement was made with the Serum Institute of India to produce over 2 billion doses annually.

8) University of Queensland and CSL - The university, along with CSL, developed the UQ-CSL v451 COVID-19 vaccine. Phase I trial of this vaccine showed a robust response towards the virus. The vaccine was developed by growing viral proteins in cell cultures. No serious side effects or safety concerns were reported in the 216 participants. Still, as participants returned false-positive test results for HIV, it was decided that the vaccine will not go into phase II/III clinical trials.

9) Beijing Institute of Biological Products and Sinopharm - Sinopharm is also testing another inactivated virus vaccine developed by the Beijing Institute of Biological Products. In June 2020, phase III trials began in the UAE and Argentina (in September). In September 2020, this vaccine was approved by UAE to use on healthcare workers.

10) Bharat Biotech, Indian Council of Medical Research, and Indian National Institute of Virology - The inactivated virus vaccine (BBV152 or Covaxin) developed by the Indian company Bharat Biotech in collaboration with the Indian National Institute of Virology began the phase III trial in October. The report on Phase I trials showed the vaccine to be safe and produce antibodies against SARS-CoV-2.

11) Medicago and GlaxoSmithKline (GSK) - GSK and Medicago developed a COVID-19 candidate vaccine combining recombinant Coronavirus Virus-Like Particles (CoVLP) with an adjuvant system. CoVLP mimics the structure of the SARS-CoV-2 virus, resulting in an immune response. Pre-clinical results using this single-dose vaccine demonstrated high levels of neutralizing antibodies.

12) CureVac and Coalition for Epidemic Preparedness Innovations (CEPI) - This company has developed an mRNA vaccine (Zorecimeran or CVnCoV), which showed antibody responses comparable to the one found in recovered COVID-19 patients. The phase IIb and III trials will begin in December 2020.

There are various other vaccines, such as INO-4800, EpiVacCorona, Lunar-COV19/ARCT-021, LV-SMENP-DC, etc., are expected to release the phase I report shortly.

Repurposed Vaccines against SARS-CoV-2:

Using an already approved vaccine (for some other infection) for protection against the new Coronavirus is called a repurposed vaccine. An Australian Institute (the Murdoch Children's Research Institute) is conducting a phase III trial using the bacillus Calmette-Guérin (BCG) tuberculosis vaccine to see its capacity to prevent COVID-19 in Australia, the Netherlands, Brazil, Spain, and the UK.

It is also believed that the polio vaccine might help the immune system to fight SARS-CoV-2, and the measles, mumps, rubella (MMR) vaccine to protect against inflammation and sepsis due to COVID-19. Nothing is proved yet.


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Frequently Asked Questions


Are Moderna and Pfizer's COVID-19 Vaccines Given in Two Doses?

Yes, both Moderna and Pfizer's vaccines are given in two doses. The time between two doses is 21 days for Pfizer's vaccine and 28 days for Moderna.


How Effective Is the Pfizer COVID-19 Vaccine?

The Pfizer vaccine is 95 % effective at preventing symptomatic COVID-19 cases, according to the FDA.


How Effective Is the Moderna COVID-19 Vaccine?

According to the FDA, the Moderna vaccine is 94.1 % effective at preventing symptomatic COVID-19 cases.


Can Patients Currently Infected With COVID-19 Get Vaccinated?

Infected patients carry the risk of spreading the virus during vaccination. To avoid this, vaccinations should be scheduled 14 days after the resolution of symptoms.


Should Previously COVID-19 Infected People Get Vaccinated?

Yes, people who have already recovered from COVID-19 can get vaccinated. Such people already might have some level of immunity against the virus, but doctors are still advising them to get vaccinated when the vaccine becomes available to them.


Why Should People Who Have Had COVID-19 Still Be Vaccinated?

A few COVID-19-recovered patients do not seem to have a good immune response, and some reinfection cases have been reported, which is why getting vaccinated even if you were infected previously is the best thing to prevent COVID-19.


Should You Continue to Wear a Mask After COVID-19 Vaccine?

Getting the COVID-19 vaccine will prevent symptomatic COVID-19 infection, but scientists do not know if it can prevent you from spreading the virus to others. Until we know for sure, keep wearing your mask when you go to crowded places to protect others who might not have been vaccinated yet.


Can You Spread the New Coronavirus if You Get Vaccinated?

Even after getting vaccinated, you could still possibly carry and spread the new Coronavirus to others. So wear masks, maintain social distancing, and practice frequent hand-washing to protect others until the majority of the population gets vaccinated.


Can a Pregnant or Breastfeeding Woman Get the COVID-19 Vaccine?

There is no data available to determine if the COVID-19 vaccine poses a risk to pregnant and breastfeeding women. In the United Kingdom, pregnant and breastfeeding women are excluded from vaccination programs, and in the US, only women who volunteer will be given the vaccine.


What Are the Common Side Effects of COVID-19 Vaccine?

The common side effects noted so far during various drug trials are pain and swelling at the site of infection, fever, chills, headaches, and tiredness.


How Soon After Taking the COVID-19 Vaccine Are You Immune?

It can take a few weeks for the body to build immunity after getting vaccinated. So, it is possible to get infected with the new virus just before or after vaccination.


Who Will Get Vaccinated First?

With a limited supply of vaccine and scientists still trying to figure out how to safely transport big batches of vaccine, the available vaccine will be given to older adults, younger adults with comorbidities, and healthcare workers first.


Will COVID-19 Vaccine Provide Prolonged Protection?

It is too early to comment on the long-term protection of COVID-19 vaccines. While initial data from the clinical trials are encouraging, we just have to wait and watch.


Is It Compulsory to Get the COVID-19 Vaccine?

You can choose not to get vaccinated, and it is totally voluntary. But, it is advisable to receive all the doses of the COVID-19 vaccine for protection against the infection and to prevent the spread to others.

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Last reviewed at:
21 Jan 2021  -  7 min read




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