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Explained: What next for Pfizer’s Covid-19 vaccine?

Covid-19 vaccine: Pfizer has reported that its vaccine, BNT162b2, has been more than 90 per cent effective in late-stage trials. How does it work, and what do the promising results mean for the US and other countries, including India?

The company's first interim efficacy analysis signals that the vaccine is able to demonstrate an effectiveness against Covid-19. (Reuters)

US drug-maker Pfizer has released preliminary data from late-stage human trials of the Covid-19 vaccine it developed with German biotech firm BioNTech. The vaccine has been found more than 90% effective.

The findings are critical as the vaccine is headed for a review by the US Food and Drug Administration (FDA) later this month, and talks of the shot receiving emergency authorisation are closer to reality.

What type of vaccine have Pfizer and BioNTech developed?

This is a vaccine that was developed using mRNA technology — it makes use of the messenger RNA molecules that tell cells what proteins to build. The mRNA, in this case, is coded to tell the cells to recreate the spike protein of the novel coronavirus. Once the mRNA is injected into the body, the cells will use its instructions, creating copies of the spike protein, which is in return expected to prompt the immune cells to create antibodies to fight it.

Unlike several other vaccine candidates, mRNA vaccines are synthetically developed — they don’t need the virus to be cultivated and replicated, just the code for the most crucial part that the body’s immune system is to target. Another advantage is that they can be manufactured at a large scale in large vats called bioreactors.

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These are platforms that can work “on demand”, said an Indian vaccine maker who spoke to The Indian Express on condition of anonymity. After getting the code for the virus, it is possible to develop the vaccine within weeks for pre-clinical testing, compared with months taken for more traditional platforms.

What do the early results say?

The company’s first interim efficacy analysis signals that the vaccine is able to demonstrate an effectiveness against Covid-19. According to the findings, the vaccine was “more than” 90% effective in preventing Covid-19 among participants who had received a second dose as opposed to those participants who had only received a placebo.

The firm also said that analysis of the late-stage trial data showed that there were no serious safety concerns.


Considering that the US FDA as well as several international regulators and health organisations have suggested that a Covid-19 vaccine has to be able to protect at least 50% of those receiving it, the findings in Pfizer and BioNTech’s case seem promising.  📣 Express Explained is now on Telegram

“The results demonstrate that our mRNA-based vaccine can help prevent Covid-19 in the majority of people who receive it. This means we are one step closer to potentially providing people around the world with a much-needed breakthrough to help bring an end to this global pandemic,” said Albert Bourla, CEO, Pfizer, in a statement upon the release of the results.

“This is a first but critical step as we continue our work to deliver a safe and effective vaccine,” Bourla said.


The phase 3 trials of this vaccine candidate — BNT162b2 — began on July 27 and has so far enrolled 43,538 participants, 38,955 of whom had received a second dose as of November 8.

Also in Explained | Pfizer Covid-19 vaccine breakthrough: Talks with regulators next, India cold chain a challenge

Does this mean the vaccine will receive emergency approval in the US?

Not necessarily. The interim results released today were of only 94 out of nearly 40,000 volunteers who were injected with the vaccine candidate. “It’s important to note that we 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,” said Bourla.

Pfizer and BioNTech are currently accumulating this additional safety data and estimate that it will take until the third week of November for the company to make available two months’ worth of safety data following the second and final dose of the vaccine. Since this is the amount of safety data specified by the US FDA in its guidance for potential Emergency Use Authorisation, it is likely that the firms will be able to approach the regulator for emergency approval then.


Another mRNA candidate, by US firm Moderna in collaboration with the National Institute of Allergy and Infectious Diseases, has also been a frontrunner in the race towards an Emergency Use Authorisation from the US FDA. The firm also expects the required readout from late-stage human trials later this month, and can reportedly approach the regulator for an EUA towards end-November.

Also in Explained | Status check: Apart from Pfizer, where are we on the development of other Covid-19 vaccines?


Will India get access to the Pfizer vaccine?

So far, no. The firms have so far inked deals for hundreds of millions of doses of the vaccine with countries like the US, UK, Japan and the European Union region.

Based on current projections, the firms expect to produce globally up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021. While the Indian government had held an “initial meeting” with representatives of Pfizer’s Indian subsidiary in late August after early phase 1 data of the vaccine had come out, there has been no major movement on that front since.


The launch of this Covid-19 vaccine in India would depend on whether Pfizer and BioNTech, either on their own or through a partnership with another Indian vaccine firm, approach India’s drug regulator (Central Drugs Standard Control Organisation) for approvals to conduct human trials of the candidate here.

As per India’s regulatory requirements, a vaccine would have to undergo local trials in the country before it can receive an approval for a launch.

India is majorly focused on five other Covid-19 vaccine candidates, being tested by Serum Institute of India, Bharat Biotech, Zydus Cadila, Dr Reddy’s Laboratories and Biological E.

What major roadblocks could prevent a quick scale up of this vaccine?

The vaccine may run into logistical issues on account of cold storage — the candidate reportedly needs to be stored at temperatures below -90°F. This would require an ultra-cold storage system, as storing it at refrigerated temperatures reportedly for more than two days may render it ineffective.

This means major constraints in storage and distribution in countries like India, which is still mapping and scaling up its cold storage footprint to store even vaccines at refrigerated temperatures. Even countries with more robust cold chain systems may have to invest more to adhere to these stricter conditions.

First published on: 09-11-2020 at 06:52:10 pm
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