COVID VACCINES SO FAR

January 5, 2021 0 By FM

ChAdOx1/AZD1222

Developed by the University of Oxford and AstraZeneca, ChAdOx1 nCoV-19 vaccine (AZD1222) consists of non-replicating simian adenovirus vector ChAdOx1, containing a full-length structural spike protein of SARS-CoV-2. The vaccine, given at a dose of 5 ×10¹⁰ viral particles, is reported to be safe. However, higher reactogenicity was observed when meningococcal conjugate vaccine MenACWY was used as control. The reactogenicity was managed through 1g paracetamol given during the first 24 hours after vaccination. Cellular responses were observed 14 days after the first dose of the vaccine and on the 28th-day, spike specific antibodies were found to be at the peak. The first dose induced neutralizing antibodies in all the participants and the reactogenicity also was found to be reduced after the second dose. Overall, the two doses of vaccine were found to be sufficient to induce potent cellular and humoral immunogenicity in all the participants and no serious side effects were reported. On December 6, Serum Institute of India became the first indian company to apply for Emergency Use Authorisation for the vaccine from Drugs Controller General of India.

mRNA-1273

Developed by Moderna and NIAID, the mRNA-1273 is a lipid-nanoparticle-encapsulated, nucleoside-modified messenger RNA (mRNA)-based vaccine. It encodes the S-protein (Spike glycoprotein) present on the surface of SARS-CoV-2. The vaccine was found to generate sufficient immunogenic response and induce vigorous binding antibody responses in all the participants after the first vaccination. The immune responses were found to increase with time and increasing doses of the vaccine. Of the three doses evaluated 250 μg, 100 μg and 50 μg, the 100 μg dose elicits high neutralization responses and more favourable reactogenicity profile than the higher dose. The two-dose vaccination schedule was finalized because of its low pseudovirus neutralizing activity even after 2 weeks of the first vaccination. No serious toxicity was reported after the two-dose series of vaccination. On 19 December 2020, Moderna became the second company to get emergency use authorization for its anti-coronavirus vaccine from the US Food and Drug Administration (FDA).

Ad5-nCoV

Developed by CanSino Biological and Beijing Institute of Biotechnology, Ad5-nCoV vaccine is a type of non-replicating adenovirus type vaccine. It is found to elicit both cellular and humoral response in 95% of the participants by day 28 post-vaccination in both doses i.e., 1 × 10¹¹ viral particles and 5 × 10¹⁰ viral particles. No serious adverse reactions were reported. Apart from the results, the major obstacle that the researchers face with this vaccine candidate was the high pre-existing anti-Ad5 immunity in participants of age 55 years or more, due to which a single dose of the vaccine could not induce a high level of humoral immune responses. Therefore researchers proposed to use an additional dose of the vaccine in the older population to gain the required effect. However, the rest of the population showed better results with the single immunization at dose 5 × 10¹⁰ viral particles, making it a potential candidate for emergency vaccination. The vaccine obtained approval to be used for vaccinating Chinese military personnel in June 2020.

BNT162b1

Developed by BioNTech and Pfizer, the BNT162b1 vaccine is a lipid nanoparticle encapsulated mRNA based vaccine. It consists of the nucleoside modified messenger RNA that encodes the receptor-binding domain of the SARS-CoV-2 spike protein. The vaccine was administered at three different doses of 10 μg, 30 μg and 100 μg and exhibited an acceptable safety profile and elicited adequate antibody levels. The participants receiving two of the doses, 10 μg and 30 μg, were given a second booster dose and found to show sharper immunogenic responses.Participants who received 100 μg were not given the booster dose to avoid adverse reactions. The study is still going on. Results indicated higher reactogenicity after the booster dose. Symptoms were limited to mild to moderate in severity, which was resolved within a few days of onset. However, a conclusive inference can be drawn only after the successful completion of phase 3 trials. On 12 December 2020, the Pfizer vaccine became the first to get Emergency Use Authorisation from the US Food and Drug Administration.

Sinopharm vaccine

Developed by Wuhan Institute of Biological Products and Sinopharm, this is an inactivated whole SARS-CoV-2 virus vaccine. The phase 1 trial was conducted using three doses with 2.5 μg, 5 μg and 10 μg antigen protein content per dose. The results showed that the inactivated vaccine candidate has  a better safety profile, and that the amount of neutralizing antibodies was adequate in all three doses. No serious adverse event was reported, and only mild to moderate self-limiting reactions were reported. The phase 2 trial was conducted using the middle dose of the vaccine i.e., 5 μg antigen protein content, and the results showed that the vaccine candidate is able to effectively produce antibodies with minimal adverse reactions. However, researchers came to the conclusion that a booster dose is required to generate an adequate immunogenic response. Longer intervals (21 days and 28 days) between the first dose and subsequent booster dose generated higher antibody levels as compared to a shorter interval group (14 day schedule). On 22 July 2020, China officially approved the urgent use of the Wuhan-Sinopharm vaccine while it was still going through clinical trials.

Covaxin

It is India’s first COVID-vaccine, and is based on inactivated whole SARS-CoV-2 virus. It was developed by Bharat Biotech headquartered in Hyderabad in collaboration with the US-based company, FluGen and the University of Wisconsin-Madison. Indian Council of Medical Research (ICMR) approved the research and National Institute of Virology (NIV) at Pune provided the virus for the vaccine research. On 29 June 2020, the company got permission from Drug Controller General of India to conduct phase I and phase II human trials. Permission for phase III in 12 hospitals selected by ICMR in different cities across the country was also granted by Drug Controller General of India. The vaccine was found to generate robust immune responses, thereby preventing infection and disease in primates even upon exposure to a high amount of live SARS-CoV-2 virus. However, the complete safety and immunogenicity data of the phase II trial is still not revealed. Bharat Biotech applied to Drug Controller General seeking Emergency Use Authorisation for its vaccine on 8 December 2020.

Sputnik V

It is a type of non-replicating adenovirus (rAd26-S+rAd5-S) vaccine developed by the Russian government’s Gamaleya Research Institute of Epidemiology and Microbiology in Moscow. The vaccine consists of two components, one with the recombinant adenovirus vector based on the human adenovirus type 26, and another with the adenovirus vector based on the human adenovirus type 5, both containing the protein gene for SARS-CoV-2 S. This was registered on 11 August 2020 and became the first vaccine against COVID-19 on the market. The vaccine is reported to have cleared phase 1 and 2 clinical trials in humans. The first component was given as the first vaccination dose and the other component was given as the second dose to all the participants. No
unwanted side effects were reported and the vaccine is said to induce strong antibody and cellular immune response. Currently, there are plans to execute the phase 3 trial in various other countries like UAE, India, Venezuela, Egypt and Brazil. On 13 October 2020, Dr Reddy’s Laboratories re-applied for approval from Drug Controller General for conducting phase 2 and 3 clinical trials of Sputnik V.

ZyCoV-D vaccine

It is India’s second vaccine, and is a type of DNA plasmid vaccine expressing SARS-CoV-2 S protein. It is developed by Zydus Cadila Healthcare Ltd headquartered in Ahmedabad, Gujarat. The company got permission from Drug Controller General of India to conduct human trials in July 2020. Currently, the phase II trial of the vaccine is underway. The phase I trial
of the vaccine was conducted on healthy volunteers and was reported to be safe in all the participants. On 4 December 2020, the company announced that it had received approval from Drug Controller General to start the phase III clinical trial of Pegylated Interferon alpha-2b, registered as ‘PegiHep’.