December , 2020
Covid-19 vaccines: Top contenders, side effects and priority
11:23 am

Aritra Mitra

Researchers have been working worldwide to find a vaccine against SARS-CoV-2, the virus causing the Covid-19 pandemic. The pandemic has created unprecedented public/private partnerships with a few vaccines receiving authorisation till now. Operation Warp Speed (OWS) is a collaboration of several US federal government departments including Health and Human Services and its sub agencies and the private sector. OWS has selected three vaccine candidates to fund for Phase III trials: Moderna’s mRNA-1273, University of Oxford and AstraZeneca’s AZD1222, and Pfizer and BioNTech's BNT162.  In India, five of the 30 vaccine candidates developed are in clinical trials. They include the Oxford-AstraZeneca vaccine which is being tested by Serum and Covaxin developed by Bharat BioTech. From December 8, Britain started giving first doses of the Pfizer/BioNTech vaccine.

Following is a chart listing the top contenders for the Covid-19 vaccine:




Trial Phase



mRNA-based vaccine



Phase 3

Multiple study sites in Europe, North America and China


mRNA-based vaccine


Phase 3

Kaiser Permanente Washington Health Research Institute


Recombinant vaccine (adenovirus type 5 vector)

CanSino Biologics        

Phase 3

Tongji Hospital’ Wuhan; China


Replication-deficient viral vector vaccine (adenovirus from chimpanzees)

The University of Oxford; AstraZeneca; IQVIA; Serum Institute of India           

Phase 3

The University of Oxford, the Jenner Institute


Inactivated vaccine (formalin with alum adjuvant)


Phase 3

Sinovac Research and Development Co., Ltd.


Inactivated vaccine           

Bharat Biotech; National Institute of Virology     

Phase 3


JNJ-78436735 (formerly Ad26.COV2.S)           

Non-replicating viral vector     

Johnson & Johnson          

Phase 3

Johnson & Johnson

No name announced      

Inactivated vaccine           

Wuhan Institute of Biological Products; China National Pharmaceutical Group (Sinopharm)   

Phase 3

Henan Provincial Center for Disease Control and Prevention


Nanoparticle vaccine           


Phase 3


Sputnik V       

Non-replicating viral vector     

Gamaleya Research Institute, Acellena Contract Drug Research and Development  

Phase 3




Side effects

A latest report on by James Gallagher, health and science correspondent titled ‘Covid vaccine: What you need to know about vaccine safety’ stated that Pfizer claimed the efficacy of its vaccine candidate is about 95%. However, it has very common side-effects including pain from the injection, headache, chills and muscle pain. These could affect more than one in 10 people. It was also reported that two people who were given the Pfizer vaccine had allergic reactions. Medical experts are of the opinion that these are all symptoms of the immune system kicking into gear which can be managed with paracetamol. Dr Penny Ward, from King's College London and the Faculty of Pharmaceutical Medicine also said to, “The MHRA are very experienced, we can be reassured if the regulator says the benefits clearly outweigh the risks, that should be the end of it really.”

The report on mRNA-1273 on stated that the phase III study of the vaccine met with 94.5% efficacy. The report further stated, “A review of solicited adverse events demonstrated that the vaccine was generally well tolerated; majority of adverse events were mild or moderate in severity and the solicited adverse events were generally short lived.” According to the report, “Grade 3 (severe) events greater than or equal to 2% in frequency after the first dose included injection site pain (2.7%), and after the second dose included fatigue (9.7%), myalgia (8.9%), arthralgia (5.2%), headache (4.5%), pain (4.1%) and erythema/redness at the injection site (2.0%).”

The press release issued by AstraZeneca stated, “One dosing regimen (n=2,741) showed vaccine efficacy of 90% when AZD1222 was given as a half dose, followed by a full dose at least one month apart, and another dosing regimen (n=8,895) showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens (n=11,636) resulted in an average efficacy of 70%. All results were statistically significant (p<=0.0001). More data will continue to accumulate and additional analysis will be conducted, refining the efficacy reading and establishing the duration of protection.” An independent Data Safety Monitoring Board determined that the analysis met its primary endpoint showing protection from Covid-19 occurring 14 days or more after receiving two doses of the vaccine. No serious safety events related to the vaccine have been confirmed. AZD1222 was well tolerated across both dosing regimens.

The data available on about 20,000 people who were immunised in the Pfizer trial, 15,000 for the Moderna vaccine and 10,000 for the one developed by Oxford/AstraZeneca is enough in showing that the vaccines work and detect the common problems. However, there can be cases where the vaccines may not be able to pick up something that affects one-in-50,000 people who are immunised. It is always possible that vaccines have health consequences that have not yet become clear. Dr. Ward pointed out that it is almost impossible to spot an extremely rare side effect before licence and without a trial of millions of people.

Who will get it first?

General principles regarding who will get vaccinated first have been discussed for months. on their website stated after their vaccine candidate is authorised for emergency use, the government and the health authorities would first offer the vaccine to those who have the greatest need. In the US, the U.S. Centers for Disease Control and Prevention (CDC) have defined the high-risk populations. It is believed that the priority will be front line healthcare workers, essential workers, immunocompromised individuals, nursing homes, and public safety officials but ultimately it is the governments that will make this determination. A report on The Washington Post titled, ‘What you need to know about the Pfizer, Moderna and AstraZeneca vaccines’ stated, “Healthy younger adults who don’t have medical conditions or high-risk jobs are likely to begin to get vaccinated starting in April, but not everyone will be able to get the shots immediately.”

In India, the deciding factor is going to be tricky. Health Minister Harsh Vardhan said that private and government health care workers and frontline workers of other departments will receive the early doses. However, experts believe that this is not going to be easy. There is an ambiguity whether a private health worker will be prioritised over a public one where majority of the healthcare is private. Whether the permanent workers will be prioritised over contractual workers also has to be decided. Further, rolling out vaccines to all the states is also going to be a problem. Whether the states worst-hit by the pandemic will get priority has to be decided. How the co-morbidities will be priorities also has to be considered. India has more than 70 million diabetics - if all of them will be given a blanket preference is under question. Furthermore, the BJP has promised the people of Bihar free vaccines as a poll promise for the recently concluded assembly elections. So, the process of distributing the vaccines throughout the country is definitely going to be a challenge for the authorities.

Challenges related to vaccination in India

Prime Minister Narendra Modi is confident about vaccinating 1.3 billion people in India. He recently said, “We have a vast and experienced vaccination network and the country will capitalise on these advantages.” In fact, India can boost of the world’s largest vaccination scheme – the universal immunisation programme. Every year, it administers vaccines for diphtheria, polio, measles and other childhood diseases to around 26 million infants and immunises about 30 million pregnant women. Still, there are certain challenges in relation to the Covid-19 vaccines in India.

A report on The Guardian titled ‘India's biggest challenge: how to vaccinate 1.3bn people against Covid-19?’ stated that India has 27,000 cold chain points (deep freezers and ice-lined refrigerators) to keep vaccines at the right temperature, 700 refrigerated trucks, around 50,000 cold chain technicians and about 2.5 million health workers to administer doses. However, in many places, the cold chain systems are not fully functional. Moreover, power cuts for long hours may leave the vaccines unfit for use.

The Guardian report adds, “Given the summer heat, the government is unlikely to opt for the Pfizer/BioNTech vaccine because its temperature requirement of -70C will be near-impossible to provide.” However, even the more standard 2-8C refrigeration requirements of the Moderna or Oxford AstraZeneca vaccines will still mean a massive scaling up of India’s existing cold chain supply. In such a way, the moment the vaccine is available, refrigerated trucks can start making the long journeys to deliver doses to every corner of the country.

BBC report ‘India coronavirus: How do you vaccinate a billion people?’ by Soutik Biswas stated that India's immunisation programme is powered by nearly four million doctors and nurses but there will be requirements for more to carry out Covid-19 vaccinations. Kiran Mazumdar Shaw, Founder of Biocon, the country's leading biotechnology enterprise, said, “I worry about how we can (extend all the resources) to rural India.”

An India Today report titled ‘India readies for 600 million Covid vaccine doses, to use standard cold storage, electoral rolls for distribution’ states that at present Indian regulators are considering three vaccines for emergency use authorisation including those from Pfizer Inc., AstraZeneca and Bharat Biotech. VK Paul, who heads the group of experts on vaccine administration for Covid-19 that advises the Indian Prime Minister stated that in a theoretical scenario, -70C capacities will have to be created where there are no such arrangements. He also informed that India will utilise its vast election machinery to deliver 600 million doses of Covid-19 vaccines to the most vulnerable people of the country in the next six to eight months.


There is no lack of ambition in India in getting the whole country vaccinated with Covid-19 vaccines but how the prevalent challenges are overcome in order to make the vaccines available has to be seen.

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