Release date:2021/8/20 11:09:37
In the field of new drug research and development, mRNA is a hot star technology. Among them, the mRNA vaccine born with the COVID-19 epidemic has attracted global attention.
Injecting a small fragment of mRNA into the human body can turn the human body into a vaccine production factory, which stimulates the immune response, thereby producing antibodies and memory cells. This unique immune method is exactly the working principle of the mRNA vaccine. In controlling the global COVID-19 epidemic, this new mechanism of vaccines has played a vital role.
However, the application of
mRNA vaccines has also encountered new challenges, the most prominent of which is to deal with the more "virulent" novel coronavirus mutant strains. At present, there are many mutant strains in the world: Alpha (B.1.1.7), Gamma (P.1), Beta (B.1.351), Delta (B.1.617.2), etc. These mutant spike proteins have been mutated, showing faster transmission than the wild type, and some of them are even more lethal.  
COVID-19 mRNA vaccine

Can mRNA vaccines that stand out from the COVID-19 epidemic take on the challenge of the COVID-19 variant?
First of all, in terms of the effectiveness of existing vaccines, the marketed mRNA-1273 (moderna) and BNT162b2 (Pfizer/BioNTech) still have a protective effect on the mutant virus.
In early May of this year, two real-world research data showed that Pfizer/BioNTech's BNT162b2 was more than 95% effective against serious diseases or deaths caused by Alpha and Beta variants. On July 21, the Department of Public Health of the United Kingdom published real-world data on the BNT162b2 vaccine against Delta variants in the New England Journal of Medicine. Data showed that after two doses of BNT162b2 vaccine, the effective rate of preventing symptomatic diseases is 88%.
Source: NEJM

Moderna's mRNA-1273 showed good data on the effectiveness of against the variant. On July 10, Moderna published real-world research data in Qatar on Nature Medcine. The data showed that two weeks after two doses of mRNA-1273, the effective rates for Alpha and Beta were 100% and 96.4%, respectively.
Nature Medcine
Source: Nature Medcine
Secondly, in terms of development, even if a new vaccine does need to be developed from the ground up, mRNA vaccines have great potential, because one of the advantages of mRNA vaccines is that they can be made quickly in the laboratory, as long as the genetic sequence of the viral protein is determined, and the generated mRNA can be packaged into a vaccine within a few weeks.  This is why mRNA vaccines have been able to rise rapidly during COVID-19.  
From now, under the circumstances that
the existing vaccines are still capable of protecting the mutant strains, it should not be the first choice of Moderna and BioNTech to develop a new vaccine against a single mutant strain. Because in addition to the effectiveness of the vaccine itself in preventing infection, there is another way to enhance the protective effect of the vaccine: inject a booster shot, that is, another shot or several shots.
On August 5,
Moderna announced the data of booster vaccination. After the third dose of mRNA-1273, the neutralizing antibodies to Beta, Gamma and Delta variants increased by 32 times, 43.6 times and 42.3 times, respectively.
Source: Moderna

The FDA also approved the emergency use authorization (EUA) for the third booster vaccination of mRNA-1273 (Moderna) and BNT162b2 (Pfizer/BioNTech) on August 13. However, this approval is aimed at specific immune-compromised people, and the general population is still only able to get two shots.
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Vaccines highly effective against B.1.617.2 variant after 2 doses
[2] Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. N Engl J Med (2021)
mRNA-1273 COVID-19 vaccine effectiveness against the B.1.1.7 and B.1.351 variants and severe COVID-19 disease in Qatar. Nat Med (2021)
Coronavirus (COVID-19) Update: FDA Authorizes Additional Vaccine Dose for Certain Immunocompromised Individuals (Source:FDA)

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[2] Overview of mRNA-Lipid Nanoparticle COVID-19 Vaccines
[3] Nature: First Confirmed That mRNA Vaccines Can Really Bring Lasting Protection
[4] Why Still Infected With The Delta Variant After Vaccination?
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