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Explained: Why AstraZeneca Halted Then Resumed Its Trial, And The Challenges In Vaccinating The Whole World

The unexplained illness of an AstraZeneca vaccine trial subject, challenges in manufacturing, storage and distribution, and the threat of Covid-19 reinfections will weigh heavy as the world raises to inoculate itself against the SARS-CoV-2 virus

Sep 14, 2020 / 02:25 PM IST

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Drugmakers are racing to come up with a vaccine to contain the Covid pandemic, which is known to have afflicted more than 28.9 million across the world and killed at least 922,735, of which 4.8 million people cases and nearly 80,000 deaths are from India. However, the recent unexplained illness of a trial subject, which led to the suspension of AstraZeneca’s vaccine trials, combined with Covid-19 reinfections and storage/distribution challenges, has raised concerns.

To be sure, vaccine and public health experts have been grappling with  these concerns all along. The compressed timelines in the race to find a vaccine may not provide enough of a window to sufficiently analyse safety and efficacy.

Here’s a reality check on the challenges in developing a safe and effective vaccine.

Why an adverse event halts a vaccine trial

Recently drugmaker AstraZeneca paused its clinical trial of Oxford University’s Covid-19 vaccine, after one of the trial participants developed a serious adverse reaction. There was no official clarification on what kind of reaction it was, or if it had anything to do with the vaccine.


COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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They were media reports stating that the ailment was Transverse Myelitis, a serious condition involving inflammation of the spinal cord, which can cause muscle weakness, paralysis, pain and bladder problems. In rare instances, transverse Myelitis can also be triggered by a vaccine.

Following a review by UK drug regulator MHRA and an independent safety review committee, AstraZeneca has now resumed its vaccine trials. But trials halted in India, Brazil, the US and South Africa are yet to resume. In India, Serum Institute of India (SII), which has partnered with AstraZeneca, is conducting phase 2/3 clinical trials.

There are a number of reactions that can qualify as suspected serious adverse reactions, symptoms that require hospitalisation, life-threatening illness and even death. But these are generally very rare. To be sure, vaccines cause side effects, most of which are mild, including soreness, swelling or redness at the injection site, and fever.


Another cause of concern is a possible reinfection of Covid-19. Recently, a 33-year-old Chinese male from Hong Kong was reportedly infected by Covid for the second time during a trip to Europe, four-and-a-half months after he first tested positive for the disease.

It was found through genomic sequencing that his second infection involved a different variant of the SARS-CoV-2 virus. While the person was found to be asymptomatic during his reinfection, his case nevertheless raised questions about antibodies waning over time and the viability of a vaccine itself.

The WHO still maintains that there is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.

But experts say the immunity induced by a vaccine is more enduring compared to that from a natural infection.

Is there enough manufacturing capacity?

The biggest global challenge is insufficient vaccine production capacity to inoculate even the most vulnerable populations. In an interview with the Financial Times, Adar Poonawalla, CEO of Serum Institute of India, the world’s largest vaccine maker, warned that there will not be enough Covid-19 vaccines available for everyone in the world to be inoculated until the end of 2024, at the earliest.

He expects the world would need 15 billion Covid-19 vaccines (two doses per person) to immunise everyone. Serum Institute has been trying to raise funds to produce 1 billion doses.

Cold storage and handling

Another big challenge in an immunisation drive is storing and handling vaccines. Many vaccines are sensitive to heat. If they are exposed to temperatures outside the recommended ranges, they lose potency and may not offer any protection. Storage and handling errors can result in the loss of patient confidence when repeat doses are required. Most conventional vaccines these days are heat-stable vaccines.

For instance, Pfizer-BioNTech’s Covid-19 vaccine, which is cruising ahead in clinical trials, has one major challenge. The mRNA vaccine cannot be stored in conventional refrigerators. Instead, it requires special ultra-low-temperature freezers that can store medicines at approximately 94 degrees below zero.

Pfizer will be making a custom-built freezer called a ‘cool box’ to distribute the vaccines and the company will remotely monitor the temperature in these boxes. This will have implications on the cost of the vaccine.

It is not known what the recommended temperature range for other vaccines is, but this will certainly be an important factor in a country like India, with its high temperatures, the absence of widespread cold-storage facilities, and likely challenges in handling the vaccines.
Viswanath Pilla is a business journalist with 14 years of reporting experience. Based in Mumbai, Pilla covers pharma, healthcare and infrastructure sectors for Moneycontrol.
first published: Sep 14, 2020 02:25 pm

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