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Vaccine summary : Three main approaches to design vaccine. 1. Use a whole virus or bacterium. 2.Just the parts of the germ that triggers the immune system 3. Just the genetic material that provides the instructions for making specific proteins and not the whole virus
This can be further categorised into different approaches. 1.Inactivated vaccine:Virus/bacteria is killed. known to be safe and scalable production. Requires special laboratory facilities to grow the virus/bacterium safely, can have a relatively long production time. (Covaxin)
2.Live-attenuated vaccine(LAV): Weakened version of the virus or one that’s very similar. Ex-measles, mumps and rubella (MMR) vaccine and the chickenpox and shingles. Can be manufactured at scale but may not be suitable for people with compromised immune systems (HIV etc). cntd.
Covi-Vac being tested in US. right now in phase-1. Further reading mentioned in the link. Not yet in use. https://clinicaltrials.gov/ct2/show/NCT04619628
3.Viral vector vaccine: This type of vaccine uses a safe virus to deliver specific sub-parts – called proteins – of the germ of interest so that it can trigger an immune response without causing disease. A particular protein is incorporated in a safe virus and then
the safe virus serves as a platform or vector to deliver the protein into the body. The protein triggers the immune response. The Ebola vaccine is a viral vector vaccine and this type can be developed rapidly. None of the popular vaccines for Covid come in this category.
The genetic approach (nucleic acid vaccine):
Uses a section of genetic material that provides the instructions for specific proteins, not the whole microbe. DNA and RNA are the instructions our cells use to make proteins. In our cells, DNA is first turned into messenger RNA,
Uses a section of genetic material that provides the instructions for specific proteins, not the whole microbe. DNA and RNA are the instructions our cells use to make proteins. In our cells, DNA is first turned into messenger RNA,
which is then used as the blueprint to make specific proteins. A nucleic acid vaccine delivers a specific set of instructions to our cells, either as DNA or mRNA, for them to make the specific protein that we want our immune system to recognize and respond to.
(Pfizer and Moderna are m-RNA based vaccines.)Here comes the interesting part that you must pay utmost attention to: Inactivated vaccine methodology has been in practice for many years. Its safety is preestablished. m-RNA based research has gained traction only due to pandemic.
Here is what WHO site says,"The nucleic acid approach is a new way of developing vaccines. Before the COVID-19 pandemic,none had yet been through the full approvals process for use in humans, though some DNA vaccines, including for particular cancers, were undergoing human trials
Research in this area has progressed very fast due to pandemic and some mRNA vaccines for COVID-19 are getting emergency use authorization, which means they can now be given to people beyond using them only in clinical trials." Link attached. https://www.who.int/news-room/feature-stories/detail/the-race-for-a-covid-19-vaccine-explained
Making an inactivated vaccine takes time and you need a predeveloped well established ecosystem to do the same but keep in mind the method is tried and tested. Given India is the hub of vaccine manufacturing in the world, we could make Co-vaxin.
The initial (Covid Virus) strain was provided by ICMR(Govt agency) to Bharat Biotech. Why making an Inactivated vaccine is difficult? Here is the reason explained via an example. First the strain needs to be identified and isolated. Take for example a flu vaccine.
After its identification, the candidate flu vaccine virus is grown for about three weeks to produce a hybrid virus, which is less dangerous and better able to grow in hens’ eggs.
The hybrid virus is then injected into a lot of fertilized eggs and incubated for several days to make more copies. Then the fluid containing virus is harvested from eggs, the vaccine viruses are killed, and the viral proteins are purified over several days.
Compared to this mRNA based vaccines are easy to develop. Why? Coz: mRNA molecules are simpler than proteins. These molecules are synthesized by chemical route rather than biological synthesis. Further reading: https://theconversation.com/how-mrna-vaccines-from-pfizer-and-moderna-work-why-theyre-a-breakthrough-and-why-they-need-to-be-kept-so-cold-150238
Now, lets come to the burning question around Covaxin: Merits in its favour: The mechanism is well established. Phase 1 and Phase 2 data available. Safe. The trial population was Indian. So, we know that the data will hold good for our population.
Only thing against it is, it is third phase of trial but please note the mechanism is safe. USA has approved Pfizer despite the fact that the mechanism is being tested on humans for the first time. So, who is taking more risk? USA or us.
Development of Co-vaxin is the hallmark of a good collaboration between the govt agency and the private sector to rise upto a national emergency by utilising our already available resources. Folks who are creating brouhaha over it are either ignorant or paid to do so.
Coming to Covishield( By SII):Covishield uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein. Ref tweet 5
The key is the viral vector: meaning which will carry the protein inside ur body. Think, it is like a capsule. So, this adenovirus can be extracted from humans or primates(animals) who are our close relatives (in terms of evolution). So, the current vaccine Covishield(SII) has
got its adenovirus(capsule that will carry the necessary protein inside ur body) from Chimpanzee. The below link provides info on its reactivity etc. Scientists have been apprehensive about its long term effect. Research urself on that. Give it a read. https://www.the-scientist.com/news-opinion/vector-based-vaccines-come-to-the-fore-in-the-covid-19-pandemic-67915
Despite this all you see is a targeted campaign against Co-vaxin. Why? Make ur own judgement. To prevent the progression of infection vaccination is the only way. Some vaccines will have some effects. What effects, I have tried to give pointers.
PS: I am just a science graduate. All the information have been collected from internet. Some more fine tuning of the information can always be done by the experts. This thread is aimed at making you read more credible sources. This is just a collation of information.
