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Explained: How Moderna’s Covid-19 vaccine works, and why DCGI nod for its emergency use is significant

With the approval for Moderna, India now has four vaccines which have been granted emergency use authorisation, the other three being Covishield, Covaxin and Sputnik V.

Written by Deeptesh Sen , Edited by Explained Desk | Kolkata |
Updated: July 6, 2021 11:21:38 am
Moderna, Moderna vaccine, Moderna vaccine in India, Moderna vaccine efficacyA man is vaccinated against Covid-19 in Govandi, Mumbai on Tuesday amid the second wave of infections. (Express Photo by Amit Chakravarty)

The Drugs Controller General of India (DCGI) Tuesday granted permission to Mumbai-based pharmaceutical company Cipla to import Moderna’s Covid-19 vaccine for restricted emergency use in the country.

At a press conference, Dr Vinod K. Paul, member (health) at NITI Aayog and chairman of the National Expert Group on Vaccine Administration for Covid-19 (NEGVAC), said: “An application received from Moderna through an Indian partner, Cipla, has been granted new drug permission for restricted use, which is commonly known as emergency use authorisation…This new drug permission for restricted emergency use is now in operation.”

Cipla had earlier sought the DCGI nod for import and marketing authorisation of Moderna jabs in India.

With Moderna’s approval, India now has four vaccines which have been granted emergency use authorisation, the other three being Covishield, Covaxin and Sputnik V.

How does the Moderna vaccine work?

After being injected into the body, the Moderna vaccine particles bump into cells and fuse to them, releasing messenger RNA (mRNA), which are genetic material that our cells read to make proteins.

The cell’s molecules read the sequence and build spike proteins. These spike proteins in turn build spikes that move to the surface of cells and protrude out their tips. The immune system recognises these protruding spikes and the fragments generated by vaccinated cells by breaking up proteins.

The mRNA, which was released by the vaccine, is eventually destroyed by the cells of the body.

When immune cells known as B cells collide with the spikes on the protein fragments, some of them lock onto these spike proteins. All they need now is activation by helper T cells after which they start generating antibodies that target the spike protein.

When the virus enters the body of a vaccinated person, these antibodies latch onto coronavirus spikes and destroy them. They also prevent infection by blocking the spikes from attaching to other cells.

How effective is Moderna’s vaccine?

Clinical trials have shown that Moderna’s mRNA-1273 vaccine has an efficacy of approximately 94.1 per cent, starting from 14 days after taking the first dose.

According to a recommendation by SAGE, the Moderna vaccine should be administered in two doses (100 µg, 0.5 ml each) at a gap of 28 days.

But studies have shown there was a high public health impact whenever the interval between the two doses has been greater than that recommended by the EUL.

Moderna has also stated that its vaccine is 96 per cent effective for adolescents in the age group of 12-17 years.

The Moderna doses can be of particular benefit to India as WHO states that countries which have a high number of Covid cases and are facing vaccine shortages can consider delaying the second dose up to 12 weeks in order to achieve a higher first dose coverage in high priority populations.

Moderna is among the four vaccines that have been included on the list approved by European Medicines Agency for the “vaccine passport” programme that will allow free movement of people in and out of Europe starting from July 1.

How long do antibodies generated by the Moderna vaccine last?

According to a recent study published in the Nature journal, mRNA vaccines such as Moderna and Pfizer can offer protection for several years after being vaccinated.

“Overall, our data demonstrate a remarkable capacity of SARS-CoV-2 mRNA-based vaccines to induce robust and prolonged … reactions,” the study states.

It also found that “vaccine-induced GC B cells are maintained at or near peak frequencies for at least 12 weeks after secondary immunization. The persistence of S-binding GC B cells and PBs (plasmablasts) in draining LNs (lymph nodes) is a positive indicator for induction of long-lived plasma cell responses.”

Moderna, Moderna vaccine, Moderna vaccine in India, Moderna vaccine efficacy A vial of the Moderna Covid-19 vaccine is seen. (AP Photo: Eugene Hoshiko, File)

How potent is the Moderna vaccine against new Covid variants?

Early studies suggest the Moderna vaccine is effective against the Alpha variant (B.1.1.7) first detected in the UK and the Beta variant (B.1.351) that was first detected in South Africa.

A study carried out by a US pharmaceutical company recently showed that immunity induced by Moderna shots successfully detected the new Covid variants, though the neutralising effect produced was stronger in case of the UK variant.

Moderna is currently exploring whether administering a third booster shot can increase protection in the light of the new variants which have emerged.

There are no study results yet which determine the Moderna vaccine’s level of protection against the Delta variant. But Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases, recently told the Washington Post that since the mRNA vaccine by Moderna vaccine has certain similarities with Pfizer, it should offer the same level of protection.

A UK study cited by the Biden administration states that one dose of the Pfizer vaccine provided about 33% protection against the B.1.617.2 variant. After two doses, the vaccine’s efficacy goes up to 88%.

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Is the Moderna vaccine safe for everyone?

WHO has stated that people with a history of severe allergic reaction to any component of the vaccine should not take the Moderna vaccine.

Assessment should be made on a case-to-case basis while administering the vaccine to “very frail older persons with an anticipated life expectancy of less than 3 months”, WHO further stated.

In the case of pregnant women, WHO has said that Moderna doses can be administered when the benefits of vaccination outweigh the potential risks.

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