Differences between various Covid Vaccines

 

Millions of doses of different Covid vaccines are now available. Which one should one get, is the question? My answer: Whichever is available in your community. All of them are effective, although none is 100% effective. It is however certain that vaccines will reduce the severity of the infection even if they cannot fully protect us against the virus.

Does everyone develop immunity after vaccination? We hope so. It depends on many factors. Individuals with less robust immune system due to factors such as age, underlying health conditions and current medications, may not develop enough protection. Some vaccines may have degraded during storage and transportation. We must be kept in mind of reports of fake vaccines that are being sold in some countries.

The race to develop and produce large quantities of vaccines against the coronavirus is on. Whereas many countries have developed vaccines and are on their way to vaccinate their respective citizens, billions of the people in the underdeveloped nations, still await their shots.

As of now, China, Russia, Europe and the United States have manufactured Covid vaccines. Each manufacturer has used a different technology, offers a different dosing schedule and may have different set of side effects. A paper in the recent issue of the  “New England Journal of Medicine” compared different vaccines that are currently available. This medical journal article is the source and basis of this blog.

Currently there are four types of coronavirus vaccines that are available:

  • mRNA
  • Viral Vectors
  • Inactivated coronavirus 
  • Spike Protein Subunit

·        The mRNA is a new technology that had never been used to successfully manufacture and market vaccines before the current pandemic. This technology involves taking the genetic code of the coronavirus spike protein, making its synthetic copy and encapsulating it in a tiny fatty particle. When injected into the body, the fatty covering dissolves releasing the synthetic messenger RNA (mRNA). Prompted by the synthetic mRNA, the body makes a protein which is the carbon copy of the real spike protein of the coronavirus. The immune system recognizes this as a foreign protein and makes antibodies (immune proteins) that protect us against the real coronavirus. The vaccines made by Moderna, Pfizer-BioNTech and GlaxoSmithKline, use the mRNA technology to manufacture their vaccines. The Moderna, Pfizer-BioNTech vaccines have completed the phase 3 trials and have been approved by the FDA for use. The GlaxoSmithKline is currently in phase 3 trials.

 

Johnson &Johnson / Janssen, AstraZeneca and the Russian Sputnik vaccines use the viral vector technology. Viruses belonging to the adenovirus family are genetically modified so that they cannot replicate. These viruses are then used as carriers (vectors) of the genomic information of the coronavirus. Once injected, the immune system makes antibodies against the genomic material delivered by the carrier viruses. J&J vaccines has been released for use after a brief suspension to study the rare side effects such as blood clots. The Russian vaccine is being used in multiple countries.

The Chinese vaccines (Sinovac and Sinopharm) use inactivated coronaviruses. The coronaviruses are grown in the virus culture in the lab and are then inactivated using various chemicals. The inactivation process makes the virus harmless but maintains its physical structure such as spikes, allowing the body to make antibodies and prevent future infection with coronavirus. China has been exporting the vaccine to many countries and has used it to vaccinate its own citizens.

The American company Novavax has developed a vaccine using the coronavirus’s spike protein subunit. A portion of the spike (subunit) is genetically engineered to make a protein. This protein is used in the vaccine to illicit the immune response and protection against the infection. The company is awaiting emergency use authorization (EUA) from the FDA.

The manufacturers are trying to stay on top as the virus mutates and new variants emerge. It seems that the current vaccines are effective against minor variation in the genomic code of the virus. If however, the mutation leads to a major change in the genomic code, then the vaccines will have to be modified accordingly.

The mRNA vaccines need two doses, 3-4 weeks apart. The J&J vaccines only need one dose to be effective. How long does the immunity lasts, is still not very well known. Based on the scientific knowledge from other viral illnesses, it is thought that one would need to be vaccinated every year just as is done with influenza vaccine.

If you have read this and have still not been vaccinated, I strongly suggest that you do. The risk of serious illness and even death is scores of times higher with Covid than it is with the vaccines.

                   Wishing all my readers, safety, sanity and good health.

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