Covaxin and Covishield were the two primary vaccines that spearheaded India’s massive COVID-19 vaccination drive. The main difference between them lies in their manufacturing technology: Covaxin is an inactivated virus vaccine developed and produced in India, while Covishield is a viral vector vaccine based on a chimpanzee adenovirus, developed by Oxford-AstraZeneca and manufactured in India by the Serum Institute of India.
Understanding the Technology Behind Each Vaccine
The core difference between Covaxin and Covishield is the scientific platform used to create them. This determines how they trigger an immune response in the body.
Covaxin: The Inactivated Virus Vaccine
Covaxin, developed by Bharat Biotech in collaboration with the Indian Council of Medical Research (ICMR), uses a traditional and time-tested vaccine technology. It contains an ‘inactivated’ or ‘killed’ coronavirus. The virus is chemically treated to make it incapable of causing disease, but its surface proteins (like the spike protein) remain intact. When injected, the immune system recognizes these proteins as foreign and produces antibodies against them, preparing the body to fight off a future infection from the live virus.
Covishield: The Viral Vector Vaccine
Covishield, developed by Oxford University and AstraZeneca, uses a newer viral vector technology. It uses a modified, harmless version of a different virus (a chimpanzee adenovirus) as a ‘vector’ or carrier. This carrier virus is genetically engineered to carry the code for the coronavirus’s spike protein. Once injected, the vector virus enters human cells and instructs them to produce the spike protein. The immune system then detects these spike proteins and generates a strong immune response against them.
A Detailed Comparison: Covaxin vs. Covishield
While both vaccines aim to protect against COVID-19, they have several differing characteristics.
| Feature | Covaxin (BBV152) | Covishield (AZD1222 / ChAdOx1) |
|---|---|---|
| Developer | Bharat Biotech (India) | Oxford University / AstraZeneca (UK) |
| Manufacturer in India | Bharat Biotech | Serum Institute of India (SII) |
| Vaccine Type | Inactivated Virus Vaccine | Viral Vector (Chimpanzee Adenovirus) Vaccine |
| Mechanism | Presents the killed coronavirus to the immune system. | Uses a harmless virus to deliver the genetic code for the spike protein. |
| Number of Doses | 2 doses | 2 doses |
| Recommended Gap Between Doses | Initially 28 days (4-6 weeks) | Initially 4-6 weeks, later extended to 12-16 weeks. |
| Efficacy (Trial Results) | Reported an interim efficacy of around 78% against symptomatic infection and 100% against severe disease. | Reported an overall efficacy of around 70-76%, which increased with a longer dose interval. |
| Storage Temperature | 2°C to 8°C | 2°C to 8°C |
Safety and Side Effects
Both vaccines were approved by Indian regulatory authorities after being deemed safe and effective. The side effects reported for both were generally mild and temporary, similar to those of other common vaccines.
Common Side Effects included:
- Pain at the injection site
- Headache
- Fatigue
- Muscle pain
- Fever
Rare side effects, such as blood clots (thrombosis with thrombocytopenia syndrome), were reported in a very small number of cases globally for viral vector vaccines like Covishield. However, health authorities, including the Ministry of Health and Family Welfare, maintained that the benefits of vaccination far outweighed the risks.
The successful rollout of these vaccines was a monumental public health achievement, requiring a deep understanding of logistics and supply chain, not unlike the process of understanding a consignment number for tracking. The technology behind them is a key topic in courses like B.Pharma.
Frequently Asked Questions (FAQs)
What is the main difference between Covaxin and Covishield?
The main difference is their technology. Covaxin is an inactivated vaccine, meaning it uses a killed coronavirus to trigger an immune response. Covishield is a viral vector vaccine, which uses a harmless different virus to carry the genetic code for the coronavirus’s spike protein into human cells.
Which vaccine is better, Covaxin or Covishield?
Both vaccines were proven to be safe and highly effective in preventing severe COVID-19 disease and death. Health experts in India advised that the best vaccine was the one that was available to you at the earliest. There was no official recommendation of one over the other for the general population.
Were the side effects different for the two vaccines?
The common side effects like fever, headache, and body ache were similar for both vaccines. Some studies suggested that the intensity of these immediate side effects might be slightly higher after the first dose of Covishield and after the second dose of Covaxin, but both were generally mild.
Why was the gap between Covishield doses longer?
The gap between Covishield doses was extended from 4-6 weeks to 12-16 weeks based on scientific data from global studies. The evidence showed that a longer interval between the first and second doses of the AstraZeneca vaccine led to a stronger and more durable immune response, increasing its overall efficacy.
Are Covaxin and Covishield approved internationally?
Both Covaxin and Covishield received Emergency Use Listing (EUL) from the World Health Organization (WHO), which facilitated their recognition by many countries around the world for international travel and other purposes during the pandemic.