CMAAO CORONA FACTS and MYTH Pfizer Vaccine : Dr K K Aggarwal

With input from Dr Monica Vasudev

India

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New Delhi, November 10, 2020 :

Pfizer Vaccine Data Show, 90% Efficacy in Early Results

A vaccine candidate against SARS-CoV-2 has been found to be 90% effective in preventing COVID-19 in trial volunteers who were without evidence of prior infection of the virus, results from an interim analysis of a phase 3 study demonstrated.

 BTN162b2, a messenger RNA–based vaccine candidate that requires two doses, is being developed by Pfizer and BioNTech SE. A global phase 3 clinical trial of BTN162b2 began on July 27 and has enrolled 43,538 participants to date; 42% of enrollees have racially and ethnically diverse backgrounds.

38,955 trial volunteers had received the second dose of either vaccine or placebo as of November 8. An interim analysis of 94 individuals conducted by an independent data monitoring committee (DMC) found that the vaccine efficacy rate was above 90% 7 days after the second dose. This means that protection was achieved 28 days after the first vaccine dose.

It validates the genetic strategy — whether its mRNA vaccines or DNA vaccines.

All of them have the same approach, which is that they introduce the gene that codes for the coronavirus spike protein into the cell. Your cell makes the spike protein, and your immune system makes antibodies to the spike protein. At least in these preliminary data, which involved 94 people getting sick, it looks like it’s effective.

According to Pfizer and BioNTech SE, final data analysis is planned once 164 confirmed COVID-19 cases have accrued. So far, the DMC has not reported any serious safety concerns. It recommends that the study continue to collect safety and efficacy data as planned. The companies plan to apply to the FDA for emergency use authorization soon after the required safety milestone is achieved.

The company cannot apply for FDA Emergency Use Authorization based on these efficacy results alone. More data on safety is also needed, and we are continuing to accumulate that safety data as part of our ongoing clinical study. At least two months of safety data following the second and final dose of the vaccine candidate is required by FDA’s guidance for potential Emergency Use Authorization and the same will be available by the third week of November.”

Administering it will be tricky. This particular vaccine has to be shipped and stored at –70° C or –80° C, which most countries have never done before. That means maintaining the product on dry ice.  [Medscape Excerpts]

1. They’re a whole new type of vaccine: It is first of its type. ‘It’s a very unique way of making a vaccine and, so far, no (such) vaccine has been licensed for infectious disease. Vaccines work by training the body to recognize and respond to the proteins produced by disease-causing organisms, such as a virus or bacteria. Traditional vaccines are made up of small or inactivated doses of the whole disease-causing organism,or the proteins that it produces, which are introduced into the body to provoke the immune system into mounting a response.

mRNA vaccines, in contrast, trick the body into producing some of the viral proteins itself. They work by using mRNA, or messenger RNA, which is the molecule that essentially puts DNA instructions into action. Inside a cell, mRNA is used as a template to build a protein. An mRNA is basically like a pre-form of a protein and its (sequence encodes) what the protein is basically made of later on.

To produce an mRNA vaccine, scientists produce a synthetic version of the mRNA that a virus uses to build its infectious proteins. This mRNA is delivered into the human body, whose cells read it as instructions to build that viral protein and therefore create some of the virus’s molecules themselves. These proteins are solitary, so they do not assemble to form a virus. The immune system then detects these viral proteins and starts to produce a defensive response to them.

2. They could be more potent and straightforward to produce than traditional vaccines

There are two parts to our immune system: innate (the differences we’re born with) and acquired (which we develop as we come into contact with pathogens). Classical vaccine molecules, usually only work with the acquired immune system and the innate immune system is activated by another ingredient, called an adjuvant. Interestingly, mRNA in vaccines could also trigger the innate immune system, providing an extra layer of defense without the need to add adjuvants.

All kinds of innate immune cells are being activated by the mRNA.

Thus the type of immune response that is triggered is very strong.

Because you’re not introducing the whole virus into the body, the virus can’t mount its own self-defence and so the immune system can concentrate on creating a response to the viral proteins without interference by the virus.

And by getting the human body to produce the viral proteins itself, mRNA vaccines cut out some of the manufacturing processes and should be easier and quicker to produce than traditional vaccines.

3. Most of what we know about mRNA vaccines comes from work on cancer

Most works on using mRNA to provoke an immune response have so far been focused on cancer, with tumor mRNA being used to help people’s immune systems recognize and respond to the proteins produced by their specific tumors.

Using tumor mRNA in this way activates the body’s T-cells – the part of the acquired immune system that kills cells, which is useful to destroy tumors. It could be important for coronavirus, too.  In viral infections, often we know that there is a need for a strong T-cell response because viruses like to hide in cells.

But to combat a virus such as SARS-CoV-2, it is likely that a different part of the acquired immune system also needs to be activated – the B cells, which produce antibodies that mark the virus out for destruction by the body.

4. There are a lot of unknowns

Outstanding questions include whether the proteins that have been chosen for the vaccine are the right ones to prevent a coronavirus infection in the body, how targeted the immune response is to this particular coronavirus, how long any immunity would last, and whether it causes side-effects such as increased inflammatory responses like redness and swelling or, in the worst case, aggravates the disease.

5. It would be possible to vaccinate on a large scale.

The manufacturing process is shorter than for other vaccines, there is potential for these vaccines to be scaled up quickly. [Excerpts from https://horizon-magazine.eu/article/five-things-you-need-know-about-mrna-vaccines.html]

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