- Oxford-AstraZeneca COVID-19 vaccine (ChAdOx1) is a viral vector vaccine
- COVID-19 vaccine Covishield uses Chimpanzee adenovirus known as ChAdOx1
- Covishield is a 2 dose vaccine given at a gap of 28 days
New Delhi: The COVID-19 vaccine ChAdOx1 nCoV-19 or AZD1222 being developed by the University of Oxford in partnership with AstraZeneca Plc is one of the two vaccines currently being used against COVID-19 in India. The Serum Institute of India (SII), the world’s largest vaccine maker by the number of doses produced, had partnered with AstraZeneca to conduct the trials in India and manufacture AZD1222. The phase 3 trials for Oxford’s COVID-19 vaccine which is called Covishield here are currently underway in India, Brazil, the United Kingdom, South Africa, Kenya and the USA. In this report, we explain the making and functioning of the Oxford COVID-19 vaccine, its efficacy and everything else that you need to know about it.
What is the Oxford vaccine and how does it work?
The Oxford-AstraZeneca vaccine is a viral vector vaccine. It is a genetically modified vaccine where a part of the SARS-CoV-2 specifically the spike protein is added to a modified version of a chimpanzee adenovirus, known as ChAdOx1. Chimpanzee adenovirus is a harmless, weakened adenovirus that usually causes the common cold in chimpanzees.
Explaining how chimpanzee adenovirus helps fight Coronavirus, Dr Rajesh Parikh, Director, Medical Research at Jaslok Hospital and the author of ‘The Vaccine Book for COVID-19’, said,
The adenovirus acts as a vehicle known as a vector to transport the spike protein into the human cell which will then trigger the immune response. It is genetically modified so that it cannot replicate.
Further elaborating on how the vaccine produces an immune response, Dr Parikh said,
After the vaccine is injected into a person’s arm, it induces an immune response. After the vaccinated cells die, the debris are stored in T cells which can recognise the spike protein when the individual is exposed to SARS-CoV-2 and induce the immune response.
The Ebola vaccine is an example of a viral vector vaccine.
How did Oxford produce a vaccine so quickly?
The teams of scientists from both the Jenner Institute and the Oxford Vaccine Group had been working on producing vaccines using ChAdOx1 or viral vector vaccine technology against a number of pathogens including flu, Zika and Middle East Respiratory Syndrome (MERS), another coronavirus.
They had already begun work on pandemic preparedness with the technology behind ChAdOx, in preparation for ‘Disease X’. When the disease emerged in China, they moved quickly. As soon as the genetic sequence was available, they began work on a trial, reads a document uploaded on the University of Oxford’s official website.
How effective is the Oxford-AstraZeneca COVID-19 vaccine?
The initial results of the Phase-III trials released in December 2020 have shown an overall efficacy of 70.4 per cent, combining data from two dosing regimens. The efficacy data is based on 11,636 volunteers across the United Kingdom and Brazil, and combined across three groups of people vaccinated – two groups who received a standard dose prime vaccination followed by a standard dose booster vaccination and one group (in the UK only) who received a low dose prime vaccination followed by a standard dose vaccination.
Suresh Jadhav, Executive Director at the Serum Institute of India told NDTV that the efficacy of the Covishield vaccine goes up if the gap between two doses is more than 28 days. He told,
Even if the difference is of four weeks, it gives good protection, but around 70-80 per cent. If the gap is increased further up to six weeks or eight weeks or 10 weeks, the results are much higher.
However, according to the latest study published in The Lancet medical journal on February 19, Covishield is more effective when the second dose is given three months after the first, instead of six weeks. As per the study, a single standard dose of vaccine provided protection against primary symptomatic COVID-19 in the first 90 days with an efficacy of 76 per cent. The findings are based on 332 cases of primary symptomatic COVID-19.
NEW—Post-hoc exploratory analyses suggest 3-month interval between doses of Oxford #COVID19 #vaccine results in higher efficacy than 6-week interval, with first dose offering 76% protection in the 3 months between doses. https://t.co/pjslBd6ncW pic.twitter.com/S3V07aV8Ri
— The Lancet (@TheLancet) February 19, 2021
How many doses of Covishield are required?
Covishield is a two dose vaccine given 28-days apart. Dr Jadhav explained that the Phase-III clinical trials that were conducted in India were done with a 28-days gap because of which this time period became the standard in the country. Dr Jadhav asserted,
While a gap of 28 days will provide a good immune response, but if you want the protection of a higher level and for a longer period, it is better to take the second dose of the COVID-19 vaccine after six to eight weeks.
What are the pros and cons of Covishield?
According to Dr Harsh Mahajan, Founder Of Mahajan Imaging and Chairman of CARINGd, since the vaccine is genetically modified so that it cannot replicate, it cannot cause the disease and is safe. The vaccine can be manufactured on a large scale and uses a well-known technology.
Another advantage of using a Covishield vaccine is that it can be stored in a fridge in a temperature range of 2 to 8 degree Celsius, which makes it easier to deliver and administer in existing healthcare settings.
Dr Mahajan believes that as of now, there is no reported disadvantage of Covishield.
What are the side-effects of Covishield?
Dr Mahajan asserted that after inoculation, some individuals may witness minor side effects like pain at the injection site, myalgia (muscle pain), fever, headache, lethargy. This is similar to the side effects that occur post any other kind of vaccination and can be overcome through minor medication.
Is Covishield suitable for people with compromised immune systems?
There is no strong evidence supporting or contraindicating the use of the vaccine in individuals with compromised immunity. It is likely that the vaccine may not be as effective. However, some immunity is better than no immunity. It is therefore recommended for this group to also take the vaccine, said Dr Parikh.
Dr K K Aggarwal, President, Confederation of Medical Associations in Asia and Oceania who got the COVID-19 vaccine Covishield three weeks ago at the National Heart Institute in Delhi shared his experience and said,
I have compromised immunity. As a doctor, I got the vaccine and I am perfectly fine.
When will Covishield be available for children?
Currently, no COVID-19 vaccine is available for children. Whenever a vaccine or drug is developed, it is first tested among adults and once the efficacy is proven, the trials are conducted among children. However, Covishield will now be tested among children and young adults aged 6-17 years. On February 12, the University of Oxford announced that it along with three partner sites in London, Southampton and Bristol, is to launch the first study to assess the safety and immune responses in children and young adults of the ChAdOx1 nCoV-19 coronavirus vaccine.
This new trial, a single-blind, randomised phase II trial, will enrol 300 volunteers, with up to 240 of these volunteers receiving the ChAdOx1 nCoV-19 vaccine and the remainder, a control meningitis vaccine, which has been shown to be safe in children but is expected to produce similar reactions, such as a sore arm, reads the official document.
Can Covishield fight virus mutations?
In an explainer video shared by the World Health Organisation (WHO) in January, its Chief Scientist Dr Soumya Swaminathan asserted that possible mutations are kept in mind while developing a vaccine as some vaccines need to be updated with the change in the strain of the virus. Explaining the same with an example, Dr Swaminathan said,
We have some vaccines, like measles, which you don’t need to change at all. You make the vaccine; it works pretty much all the time. But you also have vaccines like against the influenza virus, where you have to change the structure of the vaccine every year, based on the circulating strains and WHO coordinates this global network that actually identifies which strain should be used every year.
SARS-CoV-2 is mutating significantly but Dr Swaminathan is of the opinion that a couple of changes or mutations in the virus should not make the current vaccines ineffective. But right now, there are studies going on in labs around the world to actually confirm that, she added.
Till now, COVID-19 variant identified in the UK and South Africa had one change in common that is the N501Y mutation. According to Dr Julian W Tang, Consultant Virologist, Clinical Microbiology, University Hospitals of Leicester NHS Trust, vaccines work well against N501Y variant. However, now, there is a new UK variant, the 484k, which is causing the problem.
If the 484K starts to spread, then the existing vaccine may not be so protective. That’s why both Oxford and Moderna have proposed to change vaccines to incorporate the new mutations, said Dr Tang in a conversation with NDTV.
Dr K K Aggarwal said that scientifically the second dose of the vaccine can be given even after three months from the first dose. He is of the opinion that the companies should use these three months to manufacture a vaccine against the new strain and administer that.
NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene.
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