How exactly do Moderna, Pfizer's COVID-19 vaccines work? Top doctor explains

In a positive news related to coronavirus vaccine, two of the most promising vaccine candidates from the US-based Moderna Incm, and Pfizer Inc and BioNTech SE have revealed very high efficacy of 90 and 94.5 per cent, respectively, during the initial analysis of less than 100 participants.

Setting the bar high for AstraZeneca Plc, another prominent company that's about to release the early stage data in a few days, these two companies have raised hopes that coronavirus could be defeated sooner than we think. Both of these vaccines have been developed using the new messenger RNA or mRNA technique, and they work differently than vaccines made with traditional methods.

Dr Ali Nouri, molecular biologist and President, Federation of American Scientists, has explained how these vaccine candidates work in simplest possible way on Twitter. In mRNA technique, coronavirus or SARS Cov2 is covered with 'spike proteins', with which it grabs human cells, says Nouri. When someone is given the vaccine, the mRNA genetic material present in it instructs the human cell to make the 'spike protein'.

The mRNA is encased in a formulation of 'fatty material' that helps it get inside our cells, says Dr Nouri. The mRNA then translates into spike protein that activates our immune system to make antibodies and T cells, says Dr Nouri. If we are exposed to a virus, it just clears it by producing antibodies, he adds. The mRNA-based vaccines do not contain the virus but the 'spike portion', so there's no risk of infection either, he says.

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Is there any way to estimate immunity after using these vaccines?

Dr Nouri says the data on vaccine lifespan is yet to come out, and that two dose vaccines could provide a solution towards the problem of reinfection. "Already seeing some (though very few) re-infections after ~4 months. With other (seasonal) coronaviruses we see frequent re-infections after 12 months. Reason for the 2 dose vaccine is to boost immunity, but we'll have to wait and see how long it lasts," he adds.

Were all the participants who got vaccine shots 'symptomatic'?

Yes. "That's right. The interim analysis comprised 95 cases of symptomatic COVID-19," says Dr Nouri.

Also Read: Moderna COVID-19 vaccine 94.5% effective; can be stored in homes, clinics for 30 days

Will it be of any use for 'asymptomatic' patients?

Dr Nouri says yes it should, and that it could lower the likelihood of transmission to those who are not affected due to COVID-19 as yet. "Haven't seen data on the impact of the vaccine on asymptomatics but one would expect the vaccine to bring down viral low across the board and lower likelihood of transmission," he adds.

Also read: Pfizer, BioNTech COVID-19 vaccine found 90% effective in fighting virus

What is mRNA technique?

The "messenger RNA" technique will be used for the first time if these vaccines get the required approvals after the trials are over. Though the technique was developed in the 1990s, scientists Weissman and colleague Katalin Kariko were the first one to use the mRNA technique to address a dangerous inflammatory response seen in animals. Notably, Kariko is now a senior vice president at BioNTech and Weissan served as adviser in the company. German pharma company BioNTech developed the vaccine along with Pfizer.

Using the mRNA technique, the vaccine directs our cells to grow Covid-19 antigens or spike proteins. Seeing these spike proteins, our immune system develops antibodies without being exposed to the virus.

This new technique is believed to be safer but more expensive than the traditional ones and there's little chances of spike proteins infecting a person from COVID-19. It's also faster to develop than traditional ones and helps in the making of immune cells, which further help in building antibodies against the virus.

Also Read: '90-95% effective': Top US health expert vouches for Pfizer coronavirus vaccine's efficacy