mRNA-1273: What you need to know
The UK rollout of the Moderna COVID-19 vaccine – known as mRNA-1273 – has commenced today in Carmarthen, Wales.
mRNA-1273 is the third COVID-19 vaccine to be authorized for human use in the UK. It joins Oxford–AstraZeneca's ChAdOx1 vaccine and Pfizer–BioNTech's BNT162b2 vaccine as part of the country's large-scale vaccination program.
The Moderna COVID-19 vaccine is a messenger RNA (mRNA)-based vaccine, the same type of vaccine as BNT162b2. It contains mRNA that encodes for a specific protein from the SARS-CoV-2 virus known as the spike, or "S", glycoprotein.
When injected intramuscularly, the mRNA instructs some of the body's cells to produce S protein antigens that are recognized by the immune system and trigger antibody and T-cell production. Manufacturing the mRNA-1273 vaccine does not require any actual virus, which means that production timelines can be expedited.
Video taken from Moderna on YouTube.
How effective is the vaccine?
The vaccine is administered in two doses, 1 month (28 days) apart. The majority of evidence demonstrating the effectiveness of mRNA-1273 is derived from a large-scale, randomized, placebo-controlled and double-blind Phase III clinical trial that has enrolled ~30,000 participants aged between 18-95 years.
The interim data from the trial demonstrates an overall vaccine efficacy of 94.1% in preventing symptomatic and laboratory-confirmed COVID-19 in individuals that did not show evidence of previous COVID-19 symptoms.
In total, 11 individuals from a sample of 14,134 vaccinated people developed COVID-19 with symptoms in this data set. The trial also found that the vaccine was 100% effective in preventing severe COVID-19. Clinical testing of the vaccine did not identify serious side effects, however short-term side effects – a common occurrence with many vaccines – were noted.
What quantity of the vaccine does the UK have?
In a Tweet, the UK Prime Minister Boris Johnson said, "The Moderna vaccine rollout begins today, starting with Carmarthen in Wales. We have ordered 17 million doses that will be going into arms across the UK in the coming weeks." 17 million doses equate to the full vaccination of 8.5 million people.
What about SARS-CoV-2 variants?
The impact of SARS-CoV-2 variants on COVID-19 vaccination efforts is being closely monitored. In January, Moderna stated that studies had found "no significant impact on neutralizing titers against the B.1.1.7 [United Kingdom] variant relative to prior variants. A six-fold reduction in neutralizing titers was observed with the B.1.351 [South African] variant relative to prior variants. Despite this reduction, neutralizing titer levels with B.1.351 remain above levels that are expected to be protective."
The six-fold reduction in neutralizing titers against the South African B.1.351 variant has led the company to develop a "variant" form of the mRNA vaccine, called mRNA-1273.351. The variant vaccine delivers instructions for making the SARS-CoV-2 spike protein, just like the "original" vaccine, but it incorporates mutations that have been identified in the South African B.1.351 variant.
Last week the National Institute of Allergy and Infectious Diseases (NIAID) confirmed that a Phase I trial of the novel vaccine had commenced.