Highlights
- mRNA vaccines are called messenger RNA vaccines
- mRNA vaccines send a message to our cells to trigger an immune response
- mRNA vaccines offer a strong immune response: Dr Parikh, Jaslok Hospital
New Delhi: Countries across the globe have started coronavirus vaccination programme in a fight against the COVID-19 disease caused by SARS-CoV-2. On December 11, 2020, the U.S. Food and Drug Administration issued the first emergency use authorisation to Pfizer-BioNTech’s COVID-19 vaccine for its use in the U.S. among individuals 16 years of age and older. Soon Pfizer-BioNTech’s COVID-19 was rolled out in the United Kingdom (U.K.), Canada and several mainland European countries. Other vaccine candidates like Oxford-AstraZeneca’s Covishield, Bharat Biotech’s Covaxin, Moderna’s COVID-19 vaccine among others have also got emergency use licenses in various countries. India too initiated its coronavirus vaccination drive from January 16 with restricted emergency use provided to Covishield and Covaxin. Though all vaccines aim at providing immunity from Novel Coronavirus, they are developed differently. For example, Pfizer-BioNTech’s BNT162b2 and Moderna’s mRNA-1273 use the genetic approach and have developed mRNA (messenger-RNA) vaccines. But what is an mRNA vaccine? NDTV spoke to experts to find out an answer.
What Are mRNA Vaccines And How Do They Work?
To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies but mRNA vaccines do not work like that. Explaining mRNA vaccines, Dr Rajesh Parikh, Director, Medical Research at Jaslok Hospital and the author of ‘The Vaccine Book for COVID-19’, said,
mRNA Vaccines are in the category of, ‘Subunit, recombinant, polysaccharide, and conjugate vaccines’. These vaccines use specific parts of the infectious agent like its protein, sugar, or coating.
As the name suggests, mRNA or messenger-RNA vaccine gives a message to our cells to make a protein or even just a piece of a protein which are like those of the SARS-CoV-2 virus. The protein then triggers an immune response inside our bodies. That immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies.
Further talking about mRNA vaccines, Dr Parikh said,
Because these vaccines use very specific regions, they offer a strong immune response targeting specific regions of the infective agent. They can be used on almost everyone, including those with compromised immunity.
Elaborating more on the immunity provided by mRNA vaccines, Dr Harsh Mahajan, Founder Of Mahajan Imaging and Chairman of CARINGdx, said, as part of its immune response, a human body produces T-cells and B-cells along with antibodies. He said,
T-cells and B-cells are called memory cells and they can retain the memory of infection for life; even after antibodies have faded. Since the memory cells remember the infection, they can trigger a faster and stronger immune response if the body catches the virus. However, in the case of the COVID-19, we don’t know for how long these cells retain memory.
How Are mRNA Vaccines Different From Oxford-AstraZeneca’s Covishield And Bharat Biotech’s Covaxin?
The Coronavirus vaccine developed by Oxford-AstraZeneca is called ChAdOx1 nCoV-19 or AZD1222 or Covishield in India. It is a viral vector vaccine; such vaccines use a safe virus to deliver specific sub-parts called proteins so that it can trigger an immune response without causing disease. The ChAdOx1 vaccine uses a chimpanzee adenovirus vaccine vector that usually causes the common cold in chimpanzees and does not infect humans.
The adenovirus has been weakened to an extent where it becomes incapable of causing an infection. When a vaccine is injected, it creates antigenic reaction and antibodies are formed and immune response of the host comes in, explained Dr Mahajan.
On the other hand, Bharat Biotech’s Covaxin is an inactivated vaccine. As part of the process, disease carrying virus, in the case of COVID-19 it is SARS-CoV-2, is inactivated or killed and then injected.
Inactivated vaccines have been around for ages and one example is polio vaccine, said Dr Mahajan.
Also Read: Oxford COVID-19 Vaccine Candidate Shows 70 Per Cent Efficacy Based On Data Of 11,636 Volunteers
How Are mRNA Vaccines Developed?
Dr Mahajan informed that mRNA vaccines are manufactured in a completely synthetic manner. As per the United States’ Centers for Disease Control and Prevention (CDC), since mRNA vaccines do not use the live virus that causes COVID-19, they cannot give someone COVID-19.
How Safe And Efficacious Are mRNA Vaccines?
mRNA vaccines being produced by Pfizer-BioNTech and Moderna have undergone the same set of clinical trials as other COVID-19 vaccine candidates. Trial results and efficacy analysis demonstrates Pfizer’s BNT162b2 to be 95 per cent effective against COVID-19. Moderna’s COVID-19 vaccine is also claimed to be 94.1 per cent effective.
On December 31, the World Health Organisation (WHO) listed the COVID-19 mRNA vaccine for emergency use, making the Pfizer-BioNTech vaccine the first to receive emergency validation from WHO since the outbreak began a year ago.
Regulatory experts convened by WHO from around the world and WHO’s own teams reviewed the data on the Pfizer-BioNTech vaccine’s safety, efficacy and quality as part of a risk-versus-benefit analysis. The review found that the vaccine met the must-have criteria for safety and efficacy set out by WHO, and that the benefits of using the vaccine to address COVID-19 offset potential risks, reads an official statement from WHO.
Also Read: COVID-19 Outbreak Explained: Can COVID-19 Vaccines Fight Against Virus Mutations?
How Many Shots Of mRNA Vaccines Are Required?
Currently, both available mRNA vaccines are two dose vaccines. The second shot is given three to four weeks from the first shot. The first shot gives some immunity; the second shot is a booster dose. According to the experts, it is important to stick to the vaccine schedule.
Do mRNA Vaccines Have Any Side-effect?
Most common side effects that an individual might witness after taking any vaccine are pain, swelling and redness in the arm where the shot is given. A person may also get chills, tiredness and headache. This is the reason, it is recommended to stay put at the vaccination centre for at least half-hour after vaccine inoculation.
mRNA vaccines have slightly more side effects as compared to live attenuated or killed virus vaccines. Significant allergic reactions were reported among two nurses in the U.K. who took Pfizer vaccine shot. These might be sporadic incidence. Generally, severe reactions show within half an hour of taking the shot and they can cause death, alerted Dr Mahajan.
What Are The Pros And Cons Of mRNA Vaccines?
According to Dr Parikh, mRNA is a novel technology and it’s very safe and efficacious. Adding to this, Dr Mahajan said, since mRNA vaccines are developed in a synthetic manner, there is no limitation to the number of vaccines we can manufacture. Further talking about the disadvantages, Dr Mahajan said,
Currently, these vaccines are expensive. Secondly, they need to be stored at an extremely cold temperature like Pfizer’s vaccine requires ultra-cold chain and need to be preserved at -70 degrees Celsius. Similarly, Moderna’s vaccine needs -25°C and -15°C temperature.
According to the CDC, Moderna’s vaccine vials may be stored in the refrigerator between 2°C and 8°C for up to 30 days.
Dr Ravindra M Mehta, Senior Consultant and HOD – Pulmonology and Interventional pulmonology, Apollo Speciality Hospitals Jayanagar, noted that since the technology is being used for the first time, there is a lack of knowledge. He said,
Surprisingly, vaccines are offering over 90 per cent efficacy but there is not much data on their long-term impact. The major advantages of mRNA vaccines are not very clear right now.
Also Read: Coronavirus Outbreak Explained: What Are Mild Symptoms Of COVID-19?
Do mRNA Vaccines Alter Host’s DNA?
According to the experts NDTV spoke to and CDC, mRNA never enters the nucleus of the cell, which is where our DNA (genetic material) is kept. In fact, the cell breaks down and gets rid of the mRNA soon after it is finished using the instructions.
Do We Have mRNA Vaccines For Any Other Disease?
According to the WHO, the nucleic acid approach that delivers a specific set of instructions to our cells is a new way of developing vaccines. Before the COVID-19 pandemic, none had yet been through the full approvals process for use in humans, though some DNA vaccines, including for particular cancers, were undergoing human trials, reads the WHO’s explainer on vaccine development and distribution.
mRNA vaccines have been studied before for influenza, rabies, Zika and cytomegalovirus. Besides mRNA technology has been used in cancer research to trigger immune responses to cancer cells, explained Dr Parikh.
Essentially, the technology has been there but it is the first time a vaccine based on mRNA has been produced and is being used.
Also Read: COVID-19 Pandemic Explained: What Is Reproduction (R) Number And Why Does It Matter?
NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene.
